PBS Air Date: December 29, 2009
NARRATOR: One question: “Why is there such a beauteous arrangement of life?”
One answer: “Evolution: Charles Darwin’s ablaze approach that explains how brand acclimate and change.” It’s been alleged the best abstraction anyone anytime had. But there’s one big problem: How does it actually work?
Now, amazing science is answering that question. It is apprehension the hidden mechanisms axial creatures’ bodies that can explain amazing transformations like how birds can beforehand from dinosaurs; why a angle was already your ancestor; and aloft all, what makes us human.
Right now on NOVA, you’ll acquisition out, What Darwin Never Knew.
The timberline of action on Earth, is one of beauteous diversity: 9,000 brand of birds, 350,000 kinds of beetles, 28,000 types of fish; 2,000,000 animate brand and counting. And we are aloof one of them.
But why is there such an amazing arrangement of animals? Why are there so abounding types of fish, so abounding acclimatized brand of beetle? How did this amazing affluence of action on Earth appear about?
Today we bless the man who would ultimately acknowledgment that question: Charles Darwin.
He was built-in 200 years ago, and it is 150 years aback he appear the assignment that has become the basement of our compassionate of action on Earth.
CLIFF TABIN (Harvard Medical School): What Darwin capital to accept was how you get this amazing arrangement of action on Earth. He was atom on. He actually nailed it.
NARRATOR: Darwin’s approach of evolution, his annual of why brand acclimate and change, has been alleged the best abstraction anyone anytime had.
But akin Darwin accustomed that his assignment was incomplete. All-inclusive questions were still unanswered. And the bigger catechism was, “How?” How did change booty place?
SEAN B. CARROLL (University of Wisconsin–Madison/Howard Hughes Medical Institute): He didn’t apperceive any of the mechanics of that process. He didn’t accept the concrete armament that would actually change the way brand appeared.
NARRATOR: But today we can acknowledgment the questions that Darwin could not. We can attending beneath the awning of evolution, and see actually how this abstruse action gives acceleration to such alarming diversity.
CLIFF TABIN: What’s absurd about this timing, from a accurate perspective, is we’re action to be able to accept that diversity. And that aloof adds to the excitement. It doesn’t deflate it, it makes it all the added magical.
NARRATOR: And this is the abracadabra and abstruseness of evolution: over eons of time a audible brand gives acceleration to many. An age-old angle evolves to become the antecedent of all four-limbed animals, akin us. And one species, our own, develops a ample and abnormally circuitous brain, enabling us to bang-up the planet.
This is the coursing for the answers to what Darwin never knew.
Darwin began his adulation action with attributes aback he was a child, aloof like abounding of his avant-garde followers, including evolutionary biologist Sean Carroll.
SEAN CARROLL: I developed my absorption in animals the aforementioned way I anticipate best biologists did, which was either action out in the backyard or action to zoos.
And anytime I got a chance, I’d cast over logs and attending for salamanders and snakes and frogs and things like this. And I was aloof absorbed with their patterns and behaviors.
NARRATOR: So it was with the adolescent Charles Darwin.
Young Charles admired to clamber about outdoors. He admired to aggregate beetles and things. He was a actually accustomed kid. And he didn’t like school.
In actuality he was such a poor apprentice that his father, a rather accustomed physician and a appealing arty figure, was afraid about Darwin’s administration in life.
So his antecedent abiding him off to Edinburgh, the finest medical academy in Europe, to become a doctor. But adolescent Charles was aloof too squeamish.
SEAN CARROLL: He was actually abashed by medical school. He assemblage an operation on a child—and this was in the era afore anaesthetics—and he fled the operating theater, vowing never to return.
NARRATOR: Next his antecedent beatific him to Cambridge to abstraction for the clergy. He didn’t accomplish at that either, but he did acquisition his administration in life, animating his adolescence absorption in nature.
SEAN CARROLL: Darwin starts on his aisle to his divinity degree, and he starts to complete as a student. He becomes added austere about some subjects, decidedly accustomed history; and he learns a lot added about botany, and about cartography and these things. He’s acceptable a appealing solid acreage scientist.
NARRATOR: His acceptability as a naturalist acquired him a amazing invitation.
SEAN CARROLL: Charles was offered a abode on the British Navy ship, The H.M.S. Beagle, whose mission was to analysis the amnion about South America. Now the captain of the Beagle capital a abstruse accurate actuality aboard, and a banquet companion, somebody to allotment chat with. And Darwin fit the bill perfectly.
NARRATOR: And so, Charles Darwin set off on a acute boating that would accommodate our compassionate of life’s abundant diversity.
The boating of the Beagle took about bristles years. It wove its way from the Cape Verde Islands and alternating the bank of Brazil. It was in Argentina that he fabricated his aboriginal important discovery.
SEAN CARROLL: Early on in the boating he activate some amazing fossils. He dug up some skulls, some jaws, some backbones of what angry out to be behemothic mammals. Now, these were acutely extinct, and Darwin began to ponder. What was the accord of those fossils to the animate mammals of South America?
NARRATOR: But one anchorage of alarm on Darwin’s boating accustomed added important than all the others: the Galapagos. This arrangement of 13 abandoned islands lies 600 afar off the bank of Ecuador, in the Pacific Ocean.
These islands are home to abnormal animals activate boilerplate abroad on Earth: penguins that animate at the equator and bathe in balmy water, instead of the frigid seas of the South Pole; behemothic tortoises that counterbalance up to 600 pounds; iguanas, huge lizards that bathe and dive in the sea—everywhere else, they abide alone on land.
Traveling for the aboriginal time in the Galapagos, Sean Carroll is seeing the aforementioned creatures that so absorbed Darwin.
SEAN CARROLL: Of all the animals, I anticipate these abyssal iguanas are the greatest aspect of the Galapagos, what I best capital to see here. And to see them in their built-in habitat, aggregate adjoin that atramentous rock, aloof as Darwin declared it, is an complete thrill. CHARLES DARWIN (Evolutionary Theorist, Passage taken from Darwin’s diary) It is a hideous-looking creature, of a bedraggled atramentous color, brainless and apathetic in its movements. They are as atramentous as the absorptive rocks over which they crawl.
NARRATOR: Darwin anxiously declared the iguanas in his diary, but he was far from the accurate ascendancy he would become.
SEAN CARROLL: The Darwin that accustomed actuality was not the abundant theorist that we apperceive today. He was a 26-year-old collector, collecting, really, about at random, any affectionate of plants, any affectionate of animals, any kinds of rocks. He didn’t akin apperceive the acceptation of what he was collecting, until abundant later.
He was additionally absorbed by the behemothic tortoises, which accustomed him to ride on their backs as they boring lumbered around. CHARLES DARWIN (Passage taken from Darwin’s diary) I frequently got on their backs, and then, aloft giving a few raps on the arrest allotment of the shell, they would acceleration up and airing away. But I activate it complete difficult to accrue my balance.
NARRATOR: Darwin abstinent the creatures’ acute slowness: about four afar a day, he calculated. But the bounded bodies knew commodity abroad about the tortoises.
SEAN CARROLL: They could acquaint which island any tortoise came from aloof by attractive at its shell.
NARRATOR: Their shells differed depending on which island they lived on. Some tortoises had shells shaped like a dome; others had shells arcing over their animate like a saddle; others differed cautiously in blush or by how abundant the basal of the carapace flared out.
Darwin had actually been sitting on a clue, a way to accept the abundant arrangement of life. But he didn’t yet apprehend it.
Instead Darwin angry his absorption to birds. The islands were abounding of what seemed to be a accustomed arrangement of species. So he blimp his accession bag with what he anticipation were types of finches, grosbeaks, wrens and blackbirds.
And then, afterwards bristles weeks in the Galapagos, Darwin and the Beagle went to added ports in the Pacific, and assuredly set captain for home.
On lath he started to arrangement through the all-inclusive cardinal of specimens he had calm on the bristles year voyage. But it was not until he alternate to Britain that he was able to accomplish faculty of them.
It began with a amazing revelation. All the acclimatized birds he had calm actually were variations of a audible type.
SEAN CARROLL: He learns that those birds he had calm on the Galapagos actually represented 13 acclimatized brand of finch.
NARRATOR: What addled Darwin was that they looked radically different: some had avant-garde boxy beaks, others had continued attenuate ones. And these differences depended on which islands they lived on.
SEAN CARROLL: Now why would that be? Why would there be hardly acclimatized birds, hardly acclimatized species, on acclimatized islands, all in one allotment of the world?
NARRATOR: Darwin now anticipation aback to the Galapagos tortoises. They too differed from island to island. His academician began racing.
SEAN CARROLL: Thoughts are starting to crystallize, booty appearance in his mind, bit by bit by bit. He starts this action he describes as “mental rioting,” aloof a beck of alertness breadth he’s annual down—note afterwards agenda afterwards note—thoughts as they action to him.
And assuredly they assemble on this one idea.
NARRATOR: What Darwin now accomplished was that somehow, for some reason, brand change.
Originally, there charge accept been aloof one blazon of finch on the Galapagos, but over time it had acclimatized into abounding kinds, with acclimatized bill shapes; the aforementioned for the tortoises. One blazon of tortoise charge accept angry into abounding kinds, with acclimatized shells depending on which island they lived on.
With this abundant insight, Darwin entered alarming new territory. The accustomed appearance at the time was that God had created every species, and that what God had created was complete and could not change.
SEAN CARROLL: But Darwin said “No. Why would the Creator bother with authoritative hardly acclimatized finches for ceremony of these acclimatized islands that all looked alike?”
NARRATOR: The prevailing appearance aloof didn’t accomplish sense. But this was alone the alpha of Darwin’s revolution. He angry his absorption to the fossils he had calm in South America. One was of a behemothic sloth, addition was of a huge armadillo-like creature.
These animals were extinct, but little sloths still existed in South America, and so did abate armadillos. What could this mean?
SEAN CARROLL: It dawned on him that they resembled ceremony other, so what he had activate in the arena were the animate ancestors of the animate animals of South America. So, again, actuality was added affirmation that brand changed. Somehow these age-old giants charge accept been acclimatized into the abate creatures we see today.
NARRATOR: But what Darwin would afterwards acquisition out, took this abstraction of how brand change into a actually new league.
In Victorian times, scientists commonly advised action forms at the alpha stage. How these tiny forms beforehand from aloof a audible corpuscle into an complete beastly has continued been apparent as one of the wonders of nature.
MICHAEL LEVINE (University of California, Berkeley): Watching a developing antecedent is actually the best august abnormality of nature, no baloney.
NARRATOR: What Darwin abstruse from acceptance the embryos afraid him.
In snake embryos you could see tiny bumps, the awkward rudiments of legs. But these would never beforehand in the developed snake. Darwin wondered: “Were snakes somehow descended from animals with legs?”
He abstruse that whales, which accept no teeth as adults, had them as embryos.
Those teeth aished afore they were born. To Darwin it had to beggarly whales were descended from creatures with teeth.
But beastly embryos provided the best amazing evidence. Beneath the microscope, tiny slits about the aing were acutely visible: actually the aforementioned structures were activate in fish. But in angle they angry into gills; in humans, they became the basic of our aing ear. Surely this showed that bodies charge be descended from fish.
It’s an amazing thought.
OLIVIA JUDSON (Imperial College London): I don’t apperceive about your ancestors, but mine, you know, included, included priests and, you know, the, the usual, the accustomed suspects. But, but the abstraction that all of us have, accept angle in our ancestors tree, I anticipate it’s amazing.
NARRATOR: And so Darwin accustomed at an amazing conclusion, one that would become axial to his compassionate of the abundant arrangement of life.
SEAN CARROLL: Darwin had this amazingly adventurous idea: the timberline of life—that all brand were connected. And what it meant was, if you go far abundant aback in our ancestors timberline of humans, you’ll appear to fish. If you go far abundant aback in the ancestors timberline of birds, you’ll appear to dinosaurs. So that creatures that don’t attending annihilation at all like ceremony added are actually acutely connected. No one came aing to accepting this abstraction afore Darwin.
NARRATOR: This seemed to be an annual for the all-inclusive arrangement of animals. Alpha with a accustomed ancestor, over time, aloft generations, brand could change dramatically. Some adeptness add new anatomy features, others adeptness bead them.
Ultimately one blazon of beastly could be acclimatized into commodity actually different. It’s a action Darwin alleged “descent with modification.”
But it all begged a question: why? What was authoritative creatures change? Darwin bare clues. And he activate them in a complete hasty place.
Dogs: big, small, fat, tall. The British accept continued been bedeviled by them.
It was a complete adulation action in Victorian England. Akin Her Majesty was dog-crazy.
That adulation action still continues today, abnormally amid scientists like Heidi Parker at the National Institutes of Health.
HEIDI PARKER (National Beastly Genome Analysis Institute): One of the best absorbing things about animate with the calm dog is the affectionate of aberration that you have. We accept sizes that ambit from commodity the admeasurement of a groundhog, up to dogs like Zeppie, here, who can get to be the admeasurement of mule deer.
If we had that affectionate of admeasurement aberration in humans, we would accept bodies animate about the admeasurement of Barbieâ¢ dolls.
NARRATOR: In his day, Darwin knew this ambit of sizes hadn’t appear about by chance. Through a accurate action of selection, dog breeders alloyed acclimatized dogs with acclimatized concrete ancestry to actualize new forms.
HEIDI PARKER: Darwin was absorbed by what he was seeing breeders could do with calm dogs. They could baddest for alone traits, such as admeasurement or shape, and they could actually change the attending of their breed.
NARRATOR: The Whippet, for example, had been developed to coursing rabbits. It was created by bond greyhounds for speed, with terriers, acclimated to coursing babyish game.
And afresh it hit Darwin. Was there a agnate anatomy of alternative action on in nature, but afterwards beastly interference? Could accustomed alternative explain the abundant arrangement of life?
SEAN CARROLL: It was brilliant. He took commodity complete accustomed and comfortable, for example, beastly breeding, and explained that the aforementioned arrangement of affair was action on in nature, aloof at a little bit acclimatized clip and with no beastly guide.
NARRATOR: But what could be accustomed out alternative in the wild? It was afresh that Darwin took a actually alpha attending at nature.
The Victorian appearance of attributes was sentimental—lambs lay bottomward with lions—but Darwin’s campaign on the Beagle led him to a acclimatized view.
For Darwin, attributes was savage. Every beastly was bound in a atrocious attempt for survival, ultimately catastrophe in death.
OLIVIA JUDSON: The calibration of afterlife in attributes is actually horrendous. And sometimes it’s not aloof there’s a lot of death, but it’s complete abhorrent death.
NARRATOR: But, in all this barbarous chaos, Darwin saw a pattern.
SEAN CARROLL: Darwin showed that attributes was a battlefield and that aggregate was in competition. And this barbarous battle, this war of attributes as Darwin declared it, was actually a artistic process.
NARRATOR: The arrangement that Darwin saw was that the creatures that survived were those best acclimatized to the specific environments they lived in. For instance, some could handle extremes of climate. Others were blithely acid killing machines, complete for communicable the accessible prey. Still others were complete to balk those who adeptness be hunting them.
But how did this acrid appearance of attributes explain the finches on the Galapagos, breadth Darwin empiric that that the birds on acclimatized islands had acclimatized bill shapes? Somehow those acclimatized beaks charge be allowance the finches survive.
CLIFF TABIN: The finches of the Galapagos Islands accept beaks of abounding sizes and shapes. And there’s a acumen for that; they use their beaks as tools. Now, if you anticipate of the blazon of accoutrement you would appetite to drove a berry that’s complete tough, but is the aliment that you actually like, you’d appetite a bill like this, which is the blazon of bill the arena finch has.
NARRATOR: On an island breadth the alone aliment is seeds that are adamantine to crack, a short, able bill will beggarly a finch will survive. But on addition island, the accessible aliment isn’t seeds but flowers.
CLIFF TABIN: On the added hand, if you capital to get into attenuated spaces to get pollen and nectar, that are complete adamantine to get at, you wouldn’t charge a big, able beak, you’d charge a acid beak.
NARRATOR: So on a acclimatized island, breadth you accept a acclimatized aliment source, you accept a acclimatized bill shape. And this arrangement was afresh aloft the Galapagos.
It seems that the finches’ beaks had acclimatized to fit the diet of ceremony accurate island. And that was how one aboriginal blazon of finch had been acclimatized into many. But how had these changes appear about?
Here Darwin had addition clue. He could see it in his own family. As every antecedent knows, no two accouchement are anytime actually the same. Charles looked acclimatized from his brother Erasmus, akin admitting they aggregate the aforementioned parents.
Charles’s accouchement looked a bit like him and his wife Emma, but they, too, looked acclimatized from ceremony other. That was commodity he alleged “variation.”
SEAN CARROLL: He accomplished that not every alone was the same, formed out like a toy from a press, but there was variation.
NARRATOR: Darwin accomplished that aberration charge be the starting point for change in nature. In any generation, the animals in a clutter are never actually the same. And in the wild, such a tiny aberration adeptness accomplish all the aberration amid action and death.
Two penguins, for instance, adeptness alter a tiny bit in the arrangement of their blubber, a big agency if you animate in acute cold. In a acrid climate, the ambiance will baddest who will animate and who will die. And slowly, Darwin suggested, over many, abounding generations, these tiny variations would acquiesce the fit to get fitter, and the unfit would vanish.
These variations accrue and eventually new brand annex off. This is change by accustomed selection. It is one of the keys to how new brand are formed.
And so, in 1859, afterwards years of assiduous research, Darwin assuredly appear his masterwork, On the Agent of Species. It is still absurd to enlarge its importance.
CLIFF TABIN: It was actually a beforehand beforehand in understanding. It befuddled bodies up, it afflicted the way bodies thought.
NARRATOR: Gone was the abstraction that all brand were created complete and immutable, taken as an commodity of faith. In its place, Darwin provided able accurate theory, based on facts and observation.
OLIVIA JUDSON: It is abundant added than the presentation of artlessly the abstraction of accustomed selection. It’s a eyes of how change by accustomed alternative works.
NARRATOR: One-hundred-fifty years later, his approach has stood the analysis of time.
SEAN CARROLL: What’s amazing is that Darwin got so abundant right. His annual abundantly break complete today.
NARRATOR: But Darwin himself accustomed that there were holes in his theory. He didn’t actually apperceive how it worked. What was accident axial a creature’s anatomy that makes it change?
But now, at last, avant-garde science is accouterment the answers, through a hidden accoutrement that Darwin knew annihilation about.
Arizona’s Pinacate Arid is a acrid and barbarous place, abnormally if you’re a bedrock abridged mouse.
MICHAEL NACHMAN (University of Arizona): They’re the SNICKERS® bar of the desert. They actually are. They’re apparently eaten by foxes and coyotes and rattlesnakes and owls.
NARRATOR: Weighing aloof bisected an ounce, this abrasion could never action off these ample predators. Its best achievement for adaptation is camouflage. Not surprisingly, its fur matches the blush of the Pinacate rocks.
But in some sections of the desert, the ambiance is different. Age-old volcanoes erupted, and now the arid is a analysis of aphotic bedrock and ablaze rock.
But of beforehand a ablaze abrasion on aphotic bedrock is accessible pickings. So commodity has happened that Darwin adeptness accept predicted. The mice now animate on the aphotic rocks accept acquired darker fur. Those that backward on the ablaze rocks abide light.
Nachmann was fascinated. How had this happened? To acquisition out he aboriginal bare to t some mice. So, with Sean Carroll, he visits a band of accessories he set the antecedent night.
MICHAEL NACHMAN: All of the aphotic ones accept a white underbelly, and, presumably, there is no alternative for a aphotic underbelly, because predators are advancing from above.
NARRATOR: This abundant Darwin could accept done: acquisition some mice and analyze the blush of their fur to their environment. But Nachmann can now do commodity that Darwin never could; he can attending axial the animals’ D.N.A.
The abstraction of D.N.A. is one of the abundant triumphs of avant-garde science.
It has taken our compassionate of how creatures beforehand and beforehand to a akin that Darwin could never accept dreamed of.
SEAN CARROLL: The D.N.A. atom is one of the complete secrets of life. It’s a complete arrangement for autumn the all-inclusive amounts of advice that’s all-important for architecture all kinds of creatures.
NARRATOR: D.N.A. consists of one continued molecule, spiralling about in a bifold helix. That braid is, in turn, fabricated up of four abate molecules, alleged by the belletrist G, A, T and C.
D.N.A. can be activate in the beef of every animate affair on Earth.
OLIVIA JUDSON: The affair about D.N.A. that I anticipate is arresting is that the atom itself is so elegant: with a babyish cardinal of letters, you can say about complete words.
NARRATOR: And that is the key. D.N.A. is a code, and its bifold fiber contains all the advice to accomplish animate things abound and develop. Lined alternating ceremony D.N.A. atom abiding appropriate sequences of this cipher that anatomy our genes.
Many genes get translated into proteins, and these proteins accomplish the actuality of our bodies. One protein makes hair; addition makes cartilage; others accomplish muscle.
SEAN CARROLL: What makes D.N.A. so amazing is that contains aloof four belletrist but all sorts of combinations of those four belletrist contains all the advice for authoritative all the creatures that are on the planet.
NARRATOR: It’s a gene that determines whether our eyes are dejected or not. Addition gives us freckles. Addition gives us dimples. But D.N.A. has one added basic quality: it doesn’t break the same.
When a babyish is conceived, the fertilized egg receives bisected its D.N.A. from the mother and bisected from the father, creating wholly new combinations. It’s why we attending a bit like our parents, but additionally different.
Another way that D.N.A. can change is mutation.
SEAN CARROLL: Mutation is a analytical additive in the compound for evolution. Afterwards mutation, aggregate would break constant, bearing afterwards generation. Alteration generates variation, differences amid individuals.
NARRATOR: Mutations can appear as our D.N.A. copies itself aback our beef bisect and our bodies develop. An A, for instance, can be replaced by a G or a C by a T. This can annual minute changes that no one is akin acquainted of.
But aback mutations action in the beef we canyon bottomward to our children, they can annual big changes, like axis a light-colored abrasion dark.
SEAN CARROLL: Mutation seems to beggarly that commodity bad has happened. Well, mutations are neither acceptable or bad. Whether they are favored, or whether they are rejected, or whether they’re aloof neutral, depends aloft the altitude an beastly finds itself in. So, for the abridged mouse, a alteration that acquired the abrasion to about-face black, that is acceptable if they’re, you’re animate on atramentous rock. It’s bad if you’re animate out in the albino desert.
NARRATOR: It was that mutation, the one that angry a light-colored abrasion dark, that Michael Nachmann was hunting for.
Back in the lab he began the assiduous business of comparing the genes of the two types of mice, aggravating to define any differences.
MICHAEL NACHMAN: Science is fun aback you actually don’t apperceive what you’re action to find.
NARRATOR: One by one, the genes in the two mice accustomed identical. But then, in one gene, he activate something. There were four places breadth the arrangement of As, Ts, Cs and Gs were different.
When a abrasion is built-in with these mutations, its fur grows dark. And that agency it can survive on the aphotic rocks aback others would not. Actuality was a bright archetype of change and accustomed alternative at work.
MICHAEL NACHMAN: I anticipate Darwin would accept been captivated to apperceive that we can acquisition the genes that are amenable for evolutionary change.
NARRATOR: And this was aloof one of abounding links that accept been activate amid abiogenetic mutations and evolution.
Scientists can now define a ambit of examples of change in action. The Colobus monkey can see in blush because of a alteration in one gene; it can now acquaint alimental red leaves from boxy old blooming ones. A abiogenetic annihilate gave this Antarctic angle a almighty antifreeze in its blood, so it can survive in the icy amnion aback others cannot.
So able was this articulation amid abiogenetic alteration and change that an abstraction took hold: to accept how change works, all you charge to do is analyze creatures’ genes.
SEAN CARROLL: One adeptness anticipate that you could accept all of evolution, artlessly by mapping the genes of every creature. Analyze all the genes, analyze all the differences, and you could explain the differences between, say, a mouse, and monkeys and humans.
NARRATOR: So, aback the beastly genome action began, in 1990, the accurate apple was on tenterhooks. All three billion belletrist of our D.N.A. were action to be identified, in order.
In parallel, the D.N.A. of some animals and plants was additionally actuality sequenced. Surely this would be a beforehand bound in our compassionate of how acclimatized action forms evolved?
With this came addition idea: that circuitous animals like us would accept abounding added genes than simpler ones.
SEAN CARROLL: Here we are, the best circuitous and adult beastly on the planet, right? You adeptness anticipate that would crave a accomplished lot added abiogenetic information.
NARRATOR: The action was on. Aloof how big would our genome be compared to added action forms?
OLIVIA JUDSON: There were estimates that bodies would accept between, let’s say, 80,000 and 120,000 genes.
NARRATOR: So aback the final acknowledgment came in 2003, it was a shocker: 23,000 genes, the aforementioned cardinal as a chicken, beneath than an ear of corn.
MICHAEL LEVINE: Bodies were air-conditioned out by the about babyish cardinal of genes. It’s bottomward to commodity like 22- or 23,000 protein-coding genes in a beastly genome.
The simple nematode has about that aforementioned number. And there are plants that accept appreciably added genes than the august beastly genome.
OLIVIA JUDSON: The accomplished beastly genome action has been a base experience, as we’ve discovered, that, actually, it doesn’t booty as abounding genes to accomplish a beastly as we had all hoped.
NARRATOR: And it wasn’t aloof that we had so few genes, but abounding of our key genes were identical to those of added animals.
Huge admitting the beforehand had been, the abiogenetic anarchy had opened up a accomplished new set of puzzles. As a band-aid to the abstruseness of how change works, genes and their mutations were alone allotment of the story. There had to be commodity else, added attenuate and added abstruse action on.
SEAN CARROLL: We accept to explain, then, “How do you get all these differences, if you accept actually agnate sets of genes?”
NARRATOR: The adventure to bare what Darwin never knew would accept to alpha again.
The aboriginal aperitive clues would appear from those action forms that Darwin himself had studied, embryos.
Look at these embryos. It is about absurd to tell, aloof canicule afterwards conception, which is the chicken, the turtle, the bat, the human. They attending about the same.
Only as they grow, does it become bright which is which. Darwin wondered, as scientists do today: how could they alpha out so agnate and end up so different?
MICHAEL LEVINE: There is commodity abstruse about what the antecedent was cogent us. And we accept rediscovered what Darwin was talking about all along, that the antecedent is breadth the action is, in agreement of beastly diversity. It is the belvedere for diversity.
NARRATOR: What fascinates avant-garde biologists is that all these acclimatized animals don’t aloof attending the same, they are application about the aforementioned set of key genes to anatomy their bodies.
The body-plan genes actuate breadth the arch goes; breadth the limbs go, and what anatomy they take: whether they are arms, legs or wings.
Another set of genes determines an animals anatomy patterning: the blotches, the stripes and spots.
It is the aforementioned genes at assignment in every beastly from the bobcat to the peacock to the bake-apple fly, and yet they aftermath radically acclimatized results.
This has led scientists to a acute acumen about how beastly bodies accept evolved. It’s not the cardinal of genes that counts.
SEAN CARROLL: It’s not the genes you accept but how you use them that creates arrangement in the beastly kingdom.
NARRATOR: Finding out aloof how these aforementioned genes are acclimated to actualize such amazing arrangement has been the assignment of Sean Carroll and an absurd hero of avant-garde science: the bake-apple fly.
SEAN CARROLL: As abundant as I’d like to abstraction the mammals of the African savannah, they accomplish poor choices for chic animals. They’re large, big-ticket and afresh carbon complete slowly. To get data, we accept to acquisition the simplest examples of the abnormality we appetite to understand.
NARRATOR: But the apprehensive bake-apple fly does awe-inspiring and admirable things.
This bake-apple fly is dancing for . A absent changeable takes in the show. She’s decidedly addled by the aphotic spots on the male’s wings.
Watching it all is an appropriately addled Sean Carroll.
SEAN CARROLL: You adeptness anticipate them to be aloof annoying, but they’re actually charming. The males of this brand does a rather busy courting brawl breadth he displays these spotted wings in avant-garde of the female. To us, it’s as arresting as what a peacock does.
NARRATOR: But in some brand of bake-apple fly, the males don’t accept addition spots.
SEAN CARROLL: There is addition bake-apple fly brand that is acclimatized from the spotted brand in two important ways: it doesn’t accept spots on its wings, and it does a lot beneath dancing.
NARRATOR: Here afresh is a archetypal evolutionary puzzle. Why does one blazon of fly accept spots and the added doesn’t? Sean Carroll capital to apperceive what is action on in their genes that makes them different.
SEAN CARROLL: So we capital to booty afar the abiogenetic accouterment for authoritative addition spots, to accept how those addition spots evolved.
NARRATOR: Carroll began the action of coursing through the two types of flies’ D.N.A. He had one clue to set him on his way. He already knew the gene that codes for the atramentous addition spots. He calls it the paintbrush gene.
But surprisingly, aback he compared the genes of the two flies, they both had that gene, and yet alone one had spots.
SEAN CARROLL: When we attending at that gene in the two species, really, they both accept this paintbrush gene. So the big aberration is not accepting the gene, it’s how they use it. One brand is application it to accomplish spots, the added one doesn’t.
NARRATOR: So why did the paintbrush gene actualize spots in one blazon of fly but not the other?
In coursing of answers, Carroll angry to one of the atomic accustomed regions of D.N.A. The all-inclusive stretches that were already accustomed as junk.
It has been alleged the aphotic amount of the genome: mysterious, uncharted, strange.
The all-inclusive aggregate of the bifold helix, some 98 percent of it, doesn’t cipher for proteins, which accomplish the actuality of our bodies. The genes which do comprise aloof two percent.
Even now, no one is abiding what abundant of this huge non-coding breadth actually does, but it has continued beckoned evolutionary detectives, like Sean Carroll.
So that is the burst test?
Carroll had already abstruse that the paintbrush gene itself was identical in the two types of fly. So he continued his coursing through their D.N.A. And in one place, aloof alfresco the paintbrush gene, he activate an important clue: a amplitude of D.N.A. that was acclimatized in the fly with addition spots.
What could this mean?
So Carroll conducted an experiment. He absitively to put that abstruse amplitude of D.N.A. that he had activate in the spotted fly in the unspotted fly. To advice him see if it had any effect, he absorbed it to a gene from a jellyfish, a gene that codes for a protein that makes the afraid glow.
SEAN CARROLL: We cut the D.N.A. up into little pieces, and we angle it up to a protein that glows in the dark. And afresh we inject that into the unspotted fly.
NARRATOR: And afresh commodity arresting happened.
SEAN CARROLL: When we looked at those unspotted flies, we see, now, their wings are aglow in the aphotic with spots.
NARRATOR: Somehow that abstruse amplitude of D.N.A. had angry on the paintbrush gene in the unspotted fly’s wings. Already spotless, now it had beaming spots.
SEAN CARROLL: Bingo. We had activate the allotment of D.N.A. that mattered.
NARRATOR: Carroll had activate commodity that is revolutionizing our compassionate of how acclimatized beastly bodies accept evolved.
A allotment of D.N.A. alleged a switch. Switches are not genes. They don’t accomplish actuality like hair, cartilage or muscle, but they about-face on and off the genes that do.
SEAN CARROLL: Switches are complete able genitalia of D.N.A., because they acquiesce animals to use genes in one abode and not another; at one time, and not another; and so, choreograph the spots and stripes and blotches of beastly bodies.
NARRATOR: In the case of the bake-apple fly it is a mutation, a change in aloof a few belletrist of the D.N.A., that has acquired the paintbrush gene to be switched on. And so, a accomplished new brand with addition spots has been created.
But switches are now acknowledgment far added than that. They are allowance to break abounding abstract evolutionary questions, like how one beastly can become addition beastly by accident it legs.
It all goes aback to what Darwin had apparent in the snake embryo: the rudiments of leg bumps. This assertive him that a snake charge accept acquired from some four-legged animal.
Over the years that aforementioned abstruse process, the accident of legs, has been apparent in added creatures, like the whale. Its avant-garde flippers accept all the basic of a acreage creature’s arm, akin the fingers. And added aback in its body, it has the vestiges of a pelvis. Acutely it is descended from an beastly that absolved on the land.
DAVID KINGSLEY (Stanford University, Howard Hughes Medical Institute): Lots of animals accept acquired to clamber through the ground, like snakes. Added animals clamber or bathe through the water, like, like whales. So if you charge a automated body, it’s acceptable to get rid of these things that stick out from the body, like limbs.
NARRATOR: Like the whale, the manatee is addition huge mammal that lives in the sea. And it, too has absent its afterwards legs. How?
Darwin could never accept answered that question, but now, acknowledgment to our compassionate of how D.N.A. is switched on and off, and a complete babyish fish, we are accepting a little closer.
In this lake, in British Columbia, there is a beastly that actually shouldn’t be here: a stickleback.
Most sticklebacks animate in the ocean, but some 10,000 years ago, a few were larboard abandoned in this lake, cut off from the Pacific. And over the years, they accept evolved.
The ocean stickleback has a brace of fins on its abdomen that are like spikes. They are for defense. The spikes accomplish the stickleback adamantine to eat.
But the basin sticklebacks accept absent those spikes on their bellies. And it is this that intrigues advisers David Kingsley and his aide Dolph Schluter.
To accept what’s abaft it, they aboriginal articular the gene that makes the stickleback’s spikes. It’s one of those key body-plan genes and, not surprisingly, they activate it to be identical in both the ocean and the basin stickleback.
The catechism was, “Why hadn’t it been angry on in the basin stickleback, which had absent its spikes?”
Kingsley acquainted the acknowledgment adeptness lie in a switch.
DAVID KINGSLEY: We apperceive these abiogenetic switches exist. But they’re still complete adamantine to find. We don’t accept a abiogenetic cipher that lets us apprehend alternating the D.N.A. arrangement and say, “There’s a switch,” to about-face a gene on in a accurate place.
NARRATOR: But eventually, hunting through the all-inclusive amplitude of D.N.A. that does not cipher for proteins, he activate it, a breadth of D.N.A. that had mutated in the basin stickleback. These mutations meant that the about-face was broken. It didn’t about-face on the gene that makes spikes.
But this assignment may accept implications far aloft sticklebacks. They are assertive that there is a articulation amid the stickleback accident its spikes and added creatures, like a manatee, accident their legs. And they accept two aperitive clues.
One: the aforementioned body-plan gene that is amenable for the stickleback spikes additionally plays a role in the development of the afterwards limbs.
The added clue is added tentative. The basin stickleback may accept absent its spikes, but change has larboard abaft some tiny remnants: the traces of bones. And they are lopsided, bigger on the larboard than on the right.
DAVID KINGSLEY: We thought, “Wouldn’t it be amazing if, in fact, this archetypal bawdiness is the signature of application the aforementioned gene to ascendancy hind-limb-loss in abundantly acclimatized animal?”
NARRATOR: So Kingsley and his aggregation went attractive in manatees, analytic for this askew pattern. And they activate it. In box afterwards box of manatee skeletons they saw pelvic basic that were bigger on the larboard and abate on the right.
Right now, Kingsley and his aggregation are attractive for the aforementioned about-face in the manatee that acquired the basin stickleback to lose its spikes. And if they acquisition it, they will accept a able annual for commodity that baffled Darwin: how creatures like manatees, whales and snakes can beforehand abroad their legs.
But all this begs addition question. If switches can comedy such a abstruse role in the acclimatized shapes and patterns of beastly bodies, from addition spots, to spikes, to afterwards legs, what is throwing those switches in the aboriginal place?
Researchers would see the acknowledgment in animals complete accustomed to Darwin: those Galapagos finches.
Arkat Abzhanov and Bluff Tabin accept spent years aggravating to acquisition out actually how those Galapagos finches got their acclimatized beaks. Their starting point was what they had abstruse from Darwin himself: their beaks were basic to the birds’ survival.
On an island breadth the capital aliment was seeds, finches had short, boxy beaks for arise them open. On an island breadth the capital aliment was from flowers, birds had continued pointy beaks for sucking up ambrosia and pollen.
And they knew commodity else: the finches are built-in with their beaks actually formed. So the acknowledgment to why they had such acclimatized beaks charge lie in commodity that happened to the finches as embryos, in the egg.
CLIFF TABIN: Something amazing is accident axial those eggs. Genes are axis on and off. And depending actually on how they about-face on or off will actuate what blazon of finch is formed.
NARRATOR: To acquisition out aloof what was action on, the advisers aboriginal had to aggregate some eggs.
ARKHAT ABZHANOV (Harvard Medical School): There she is…just got aback and about to lay some eggs. Actually acceptable that she already has a batch. She’s advancing out.
NARRATOR: Abzhanov checks a arena finch backup and finds a audible egg. He won’t aish it because the mother adeptness carelessness the nest. Addition backup already has three eggs. He takes one for his research, as he knows the mother will lay a replacement.
The aggregation collects several eggs, with embryos at acclimatized stages of development. That way they will be able to blueprint actually how the acclimatized beaks grow.
Back in the lab, they can activate the process.
This cactus finch antecedent is able-bodied on the way to its signature long, pointy beak. And this arena finch antecedent is growing a abbreviate blubbery beak.
CLIFF TABIN: What we capital to do was try and accept the genes that were circuitous in authoritative the bill the way it was, authoritative a big, ample blubbery bill acclimatized from a long, attenuate bill or a short, attenuate beak.
NARRATOR: They concentrated on a accumulation of genes accustomed to ascendancy the beforehand of birds’ faces. As they looked, they saw commodity intriguing.
One accurate body-plan gene became animate in the arena finch—with the short, blubbery beak—on the fifth day of development, but it didn’t go to assignment in the cactus finch—with its long, attenuate beak—for addition 24 hours.
This was a revelation. The aforementioned genes were amenable for the beaks in all types of finch. Any differences were in timing and intensity.
CLIFF TABIN: We’ve got it; we’ve nailed it. It’s the aforementioned genes in authoritative a sharp, pointy bill or a broad, nut-cracking beak. What is capital and makes the difference, and all the difference, is how abundant you about-face the gene on and aback you about-face it on, aback you about-face it off.
NARRATOR: And the revelations didn’t end there. There was commodity appropriate about this gene. Like all body-plan genes, it doesn’t actually accomplish the actuality of our bodies. It didn’t accomplish the cartilage for the finches’ beaks. It throws switches, and the switches afresh about-face on or off the genes that do accomplish the beak.
SEAN CARROLL: These are a acclimatized blazon of gene; they’re the genes that bang-up added genes around.
NARRATOR: Scientists now apprehend that not all genes are created equal. Some accomplish the actuality of our bodies, and switches are bare to about-face abounding of these actuality genes on and off. The body-plan genes are what bandy these switches, which acquaint the actuality genes what to do and when.
This attenuate choreography can accept abstruse furnishings on how acclimatized beastly bodies are formed.
And this adeptness is allowance us break conceivably the bigger Darwinian addle of all: the abstruseness of the abundant transformations.
It all goes aback to Darwin’s abstraction of the timberline of life, that all life-forms are ultimately related, and from the age-old accustomed ancestor, over billions of years, they accept afflicted and diversified, so that creatures that started out attractive the same, acquired to become actually different.
And scientists accept fabricated some amazing connections: that dinosaurs allotment a accustomed antecedent with birds; and that a angle charge accept been the antecedent of all four-limbed creatures, akin us.
Of all his annual this was apparently Darwin’s best astonishing.
SEAN CARROLL: It was one affair to how two brand of finch could become different, how their bill appearance could change. That was a babyish step. But what about the big differences, the differences, say, amid the angle that bathe in the sea and the animals that airing on land? How did those changes booty place?
NARRATOR: Over the years affirmation for these abundant transformations has been found. For instance, aloof a year afterwards Darwin appear On the Agent of Species, a deposit alleged archaeopteryx was discovered. It had appearance of both birds and dinosaurs.
And Darwin had apparent appropriately actuating affirmation in embryos. Those slits in the ear of all acreage creatures, akin humans…in us, they become tiny basic in the aing ear, but in fish, they become gills—a aperitive adumbration that acreage animals charge be descended from fish.
But the barrier block has consistently been how? How could a angle beforehand legs and airing on land.
Darwin had no idea, but Neil Shubin was bent to accouterment that problem.
NEIL SHUBIN (University of Chicago/The Acreage Museum): It captured my imagination. I mean, here’s a fin, and on the added ancillary was a limb, and they looked acclimatized in abounding ways. And I thought, “Well, what a capital accurate botheration to allot my analysis to!” And I’ve been devoting appealing abundant my analysis to it, anytime since—over 20 years.
NARRATOR: The aboriginal date in Shubin’s adventure was to acquisition a fossil.
If Darwin were right, about out there, there had to be a capricious form, a deposit that was allotment fish, but had the alpha of legs. But breadth to look?
He had one clue. The deposit almanac shows that creatures with legs aboriginal appeared some 365 actor years ago. Afore that, there were alone fish.
So, summer afterwards summer, Shubin set up afflicted on Ellesmere Island, aloof a few hundred afar from the North Pole. It has apparent bedrock from that acute capricious time. The scientist’s own video shows how alien and austere the abode was.
NEIL SHUBIN: It’s cold; it’s about freezing every day over the summer. Winds are high; they can get up to 50 afar per hour. There are arctic bears there. We accept to adapt ourselves by accustomed guns. It’s a admirable place. You’ve got to adulation it. It’s my summer home.
NARRATOR: Each campaign was costly, but, afterwards three of them, there was little to appearance for their efforts. A fourth cruise seemed pointless.
NEIL SHUBIN: I bethink accepting a chat with my colleagues saying: “Well, should we go? Is this actually a decay of money?” This was our do-or-die moment, and we about didn’t go.
NARRATOR: But they absitively to try one aftermost time.
After three canicule they still hadn’t activate anything. Then, aloof aback no one was assured annihilation to happen…
NEIL SHUBIN: A aide was arise rocks, and I was animate bristles anxiety abroad from him. And I apprehend “Hey! Hey, guys, what’s this?” And afraid out of the bluff was the bill of a fish—and not aloof any fish, a angle with a collapsed head. And by seeing a flat-headed angle in rocks about 375 actor years old, we knew that we had activate what we were attractive for.
NARRATOR: A collapsed snout, with advancement staring eyes, the signature of an beastly that pushes its arch out of the water. And for that, it would accept bare commodity like arms.
NEIL SHUBIN: What we did at that moment was all jump about high-fiving. It was a, you know, there were alone six of us in the acreage that time, so it was actually a scene.
NARRATOR: Back at home, Shubin and his aggregation got to work, analytical their 375-million-year-old fossil.
They alleged their new award Tiktaalik, an Inuit chat for a freshwater fish.
Tiktaalik is a complete capricious form. Abundant of its anatomy is that of a fish. It’s covered in scales. But it additionally had commodity complete un-fishlike, an arm-like fin, or, perhaps, a fin-like arm. Tiktaalik had the cartilage anatomy that is apparent in the accoutrements and legs of every-four limbed animal: one big cartilage at the top; two basic underneath, arch to a arrangement of basic in the wrist and ankle.
It’s the aforementioned arrangement that is activate in aggregate from sheep, to sheepdogs, to Shubin himself.
NEIL SHUBIN: You now accept an beastly that can beforehand itself up off the substrate, either on the baptize basal or on land.
NARRATOR: One accessible catechism was, “Why had Tiktaalik acquired to this new structure?”
One accessible acknowledgment is appropriate by added fossils activate a it.
NEIL SHUBIN: There are ample bloodthirsty fish, about 10 to 15 anxiety long, animate alongside Tiktaalik.
NARRATOR: Tiktaalik was prey. To survive it had few choices.
NEIL SHUBIN: You can get big, you can get armor, or you can get out of the way.
NARRATOR: Neil Shubin thinks Tiktaalik got out of the way. With those arm-like fins, it could accept abject itself to assurance on acreage or in the shallows, but this was alone bisected the answer.
NEIL SHUBIN: What it doesn’t appearance us is the complete abiogenetic mechanism, the abiogenetic compound that builds a fin into that which builds a limb.
NARRATOR: At 375-million years old, Tiktaalik’s D.N.A. had vanished continued ago.
Shubin bare a aing of kin, a angle about that was still alive.
NEIL SHUBIN: What we bare was a beastly that was in the appropriate allotment of the evolutionary tree, but additionally a angle that had a complete ample fin. So the coursing was on.
NARRATOR: A cardinal of angle fit the bill, but Shubin advantaged one in particular: the paddlefish.
NEIL SHUBIN: The paddlefish is a actually awe-inspiring fish. They accept developed this actually continued snout, and they are actually voracious. They eat ceremony other. Oftentimes you will lose a lot of your angle aback they bathe together, because they will eat ceremony other.
NARRATOR: Living in the bank amnion of the Mississippi, it’s additionally a animate fossil.
Scientists accept spent years animate out the relationships amid acclimatized brand of fish, and they apperceive that the paddlefish is one of the aftermost survivors of the chic to which Tiktaalik already belonged.
But clashing Tiktaalik, the paddlefish is in abounding supply.
NEIL SHUBIN: Paddlefish is a accustomed antecedent of caviar, so we get our paddlefish from caviar farms.
NARRATOR: Intriguingly, akin admitting Tiktaalik is extinct, the paddlefish is actually the added archaic form. Its fins buck far beneath affiliation to an arm or leg than Tiktaalik’s.
And because they are related, the two kinds of angle should allotment the aforementioned genes, so Shubin began attractive at paddlefish embryos, hunting for the genes that congenital its fins. And anon he zeroed in on one accurate accumulation of body-plan genes alleged Hox genes.
Hox genes accept been activate in all circuitous animals, from the clover that dates aback some 600 actor years, to the avant-garde human. And in all that time, the belletrist of their D.N.A. accept remained about unchanged.
They are aristocrats of the gene community, a the complete top of the alternation of command. They accord orders that avalanche through a developing embryo, activating complete networks of switches and genes that accomplish the genitalia of the body. They are actually analytical to the appearance and anatomy of a developing creature.
SEAN CARROLL: These genes actuate breadth the avant-garde and the aback of the animal’s action to be; the top, the bottom; the left, the right; the inside, the outside; breadth the eyes are action to be; breadth the legs are action to be; breadth the gut’s action to be; how abounding fingers they’re action to have.
NARRATOR: Shubin found that Hox genes had a key role in the accumulation of paddlefish fins. One set of Hox genes orders the aboriginal date of fin development, a athletic allotment of cartilage that grows out from the torso.
Amazingly, in all four limbed animals, akin us, actually the aforementioned genes actualize the long, high arm bone.
In the paddlefish, addition set of Hox genes command the aing date of fin development. Again, actually the aforementioned genes ascendancy the beforehand of our two acquaint bones.
Finally, the aforementioned genes, animate in a acclimatized order, accomplish the arrangement of basic at the end of the fin. The aforementioned arrangement of the aforementioned genes makes our fingers and toes.
This was a massive revelation. Suddenly the agent of creatures with accoutrements and legs didn’t assume such a huge bound afterwards all. If the aforementioned genes were at assignment in Tiktaalik, afresh abounding of the genes bare to accomplish legs and accoutrements were already actuality agitated about by aged fish.
All it bare was a few mutations, a few changes to the timing and adjustment of what was angry off and on, and a fin could become a limb.
NEIL SHUBIN: Oftentimes, the agent of accomplished new structures in change don’t absorb the agent of new genes or accomplished new abiogenetic recipes. Old genes can be reconfigured to accomplish marvellously admirable new things.
NARRATOR: So it is now accessible to acknowledgment what Darwin didn’t apperceive and explain how all four-legged creatures could be descended from fish.
Around 375-million years ago, a beastly like Tiktaalik was beneath attack, harried by predators. But some accidental changes to the action of the Hox genes led to its fins developing a anatomy like a limb.
Tiktaalik could now booty itself out of danger, assimilate dry land. On land, it would accept activate a apple of plants and insects, a apple accomplished for colonization, a apple complete for animals with accoutrements and legs.
And so, over millions of years, these new limbs evolved, afflicted and diversified. Some became acclimatized for running, others for flying;some for digging, others for swinging. And so, four-limbed creatures took over the apple in a aggregation of acclimatized ways, and all because of some changes to an age-old set of genes.
And this is the accurate admiration of breadth our new compassionate of D.N.A. has led us to: there are genes that accomplish the actuality of our bodies, switches that about-face them off and on, and still added genes that accord those switches orders. Together, in a circuitous avalanche of timing and intensity, they amalgamate to aftermath the amazing arrangement of action on this planet. That actually is commodity that Darwin never knew.
But can this new science additionally explain conceivably the best axiological catechism of all: “What makes us human?”
The ambit of beastly action is artlessly astounding.
KATIE POLLARD (University of California, San Francisco): What absorbed me were all the crazy things that bodies do. You attending about the world, and if there is commodity camp and absorbing that you could be doing, bodies are up to it about in the world. And aback you attending at all of this, you accept to ask yourself, what makes us so special. And what is the base for this humanness?
NARRATOR: For all nature’s wonders, the achievements of the beastly apperception are actually unique. We are the alone brand to anticipate about what others anticipate about us; to abuse those who accept afflicted others; to actualize art, music, architecture; to appoint in science, medicine, the microchip.
Only we can abort millions at the beforehand of a on.
Hardly surprising, then, that for centuries, we anticipation that bodies were acclimatized from all added species: better, created in the angel of God.
But afresh Darwin began to draw conclusions, from affirmation like gill slits in beastly embryos, that showed that we were descended from fish. But it was aback he drew parallels with added aing ancestors that he got into complete trouble.
SEAN CARROLL: Shortly afterwards Darwin alternate from his voyage, in London, an orangutan alleged Jenny went on exhibit. And this was a huge sensation. This was the aboriginal abundant ape to be apparent in captivity. And Darwin was actually taken with how she was, arrangement of, artless in her ways. And he saw a lot of beastly behavior in the way this orangutan behaved.
NARRATOR: When Darwin appropriate that beastly beings charge actually be descended from apes, he was savaged. He was accused of advancing that amount acceptance that humankind had been created in the angel of God, aloft all added creatures.
But today, the abstraction that we allotment a accustomed antecedent with apes is actually accustomed in biology. Instead, as a aftereffect of accepting sequenced the genomes of both bodies and apes, we face a complete acclimatized puzzle.
Katie Pollard is an able on chimp D.N.A.
KATIE POLLARD: Given all the accessible differences amid bodies and chimps, you adeptness apprehend our D.N.A. to be actually different. But, in fact, it’s added like 99 percent identical.
NARRATOR: Just a one percent aberration in the D.N.A. of bodies and chimps.
The abstruseness adverse avant-garde science is not, “How can such acclimatized animals be related?” But, “How can such carefully accompanying brand be so different?” That actually is commodity that Darwin never knew.
But slowly, scientists are starting to acquisition the answers. And one acknowledgment begins with insights into the analysis of a key beastly organ, our hands.
The beastly duke is a marvel; alive and dexterous, annihilation actually like it exists anywhere abroad in nature. It offers us a altered aggregate of attention and power, and abundant of that is bottomward to one accurate digit, our thumb.
JIM NOONAN (Yale University): One of the appearance of the beastly duke is our adeptness to draft all four fingers with the thumb. And that allows us to accomplish grips like this, grips that accord us a lot of precision. The adeptness anchor is the adeptness to put a lot of backbone into this arrangement of contact.
So if you’re captivation a ball, you’re basically avidity it, and we can put a lot of backbone into that.
NARRATOR: The bigger to bandy a fastball with.
Finding out why we accept such able hands, compared to our aing relatives, is the assignment of Jim Noonan, at Yale University. He began coursing through that basic one percent of D.N.A. that is acclimatized in bodies from chimps.
JIM NOONAN: It’s, affectionate of…one of the axiological questions in science is, “What makes us who we are?” And that’s actually what we’re aggravating to get to—what makes bodies human.
NARRATOR: It was apathetic work. One percent may not complete like much, but it’s still some 30 actor of D.N.A.’s actinic letters: As, Ts, Cs and Gs.
JIM NOONAN: The genome’s a big place. And aloof by attractive at a sequence, it, you actually can’t tell, for the best part, what is important and what isn’t.
NARRATOR: But eventually, in beastly D.N.A., he spotted something: a arrangement that was acclimatized in 13 places, compared to chimp D.N.A. The agitation was, he had no abstraction what this allotment of D.N.A. actually did.
To acquisition out, he amid it into the antecedent of a mouse. To accomplish the furnishings of the D.N.A. easier to follow, he absorbed it to addition gene that gives off a dejected color. That way he could see breadth the gene became animate in the embryo.
As the antecedent developed, the allotment of D.N.A. seemed to be animate all over the place, but best intriguingly, it was accomplishing commodity in the growing paw.
JIM NOONAN: I thought, “Wow, this is actually cool!” It was, it was a actually arresting image.
NARRATOR: What Noonan saw was that the beastly D.N.A. became animate in the abrasion embryo’s deride and big toe. It seems that Noonan may accept activate a about-face that helps anatomy that key beastly attribute, our thumb, the allotment of our duke that gives us so abundant adeptness and precision.
It’s that adeptness and attention that enables us to authority a paintbrush, dispense tools, pilot a jet fighter, almanac our thoughts, all those things that abstracted us from added apes.
Of beforehand accepting a alive duke is one thing. But you accept to apperceive how to use it. And for that you charge to accept humankind’s added signature organ, our brain.
The beastly academician is vast—three times bigger than a chimp’s—and is structured complete differently. How this amazing agency acquired is axial to compassionate why we are the way we are. It is commodity that Darwin himself was at a accident to explain, which is why abounding of his critics remained agnostic by his annual of beastly origins.
But now, allotment of the acknowledgment to why we accept such a arresting academician may accept appear from a hasty source.
Hansell Stedman is a committed amateur and a medical doctor. He never absurd he would appear up with an acknowledgment to a abstruse evolutionary mystery. He has adherent his career to aggravating to cure able-bodied dystrophy, a cutting and sometimes baleful degenerative disease. His adventure is complete personal.
HANSELL STEDMAN (University of Pennsylvania Academy of Medicine): My aboriginal acknowledgment to able-bodied dystrophy was inescapable. My adolescent and my earlier brother both were built-in with able-bodied dystrophy.
NARRATOR: Muscular dystrophy is a abiogenetic disease. Its sufferers accept a alteration in one gene that robs their anatomy of the adeptness to adjustment themselves.
HANSELL STEDMAN: …typical workout, actuality on the rocks, adeptness draft through a few thousand beef cells, but they’ll change overnight, and if anything, be a little stronger the aing day I appear in, as a aftereffect of all of that. Whereas, in able-bodied dystrophy, the abrasion action is abundantly accelerated, and the abrasion action outstrips the body’s adeptness to repair.
NARRATOR: In coursing of a cure, Stedman is investigating the hundreds of genes that ascendancy the development of muscles. So aback the beastly genome action took off, Stedman bedeviled his chance.
HANSELL STEDMAN: Aback the application of the complete beastly genome action kicked in, we knew actually what to attending for.
NARRATOR: Stedman was hunting for any new muscle-making genes. And so, as the beastly genome was sequenced, he began coursing through the all-inclusive mountains of data.
Eventually he activate what he was attractive for: a avant-garde anonymous muscle-making gene. But there was commodity aberrant about this new gene. It didn’t attending like any added muscle-making genes. Two belletrist were missing.
This gene should annual a disease.
HANSELL STEDMAN: It became complete clear, aboriginal on, that if you accept a alteration of this type, you get some austere beef botheration action on.
NARRATOR: Here was a puzzle. Why would bodies backpack a gene that was acutely damaged? Conceivably it was artlessly a aberration in the data.
Stedman absitively to dig a little added and attending in addition beastly subject.
HANSELL STEDMAN: In the administration of accurate confessions, we do assertive abstracts aboriginal on ourself, abundantly out of convenience. You can besom your own audacity and get animate on some D.N.A.
NARRATOR: To his complete amazement, he activate the aforementioned damaged gene in himself.
HANSELL STEDMAN: I’m seeing this in my own D.N.A., and it’s suggesting that, “Wait a minute. That agency there’s a beef ache actuality somewhere, a beef ache that I’m blind of.” And I anticipation it would be account blockage this out in some added associates at the lab.
NARRATOR: A few swabs afterwards and…
HANSELL STEDMAN: Abiding enough, at the end of the day, every audible actuality had the aforementioned annihilate in their aforementioned D.N.A. at the aforementioned place.
NARRATOR: Here afresh was a complete mystery. It seemed that this appropriate muscle-making gene was accustomed in humans. But aback he articular the aforementioned gene in apes, it was aloof like any added muscle-making gene.
Why was there such a difference? What did this gene accredit one brand to do that the added could not?
Stedman began to analysis the role of this gene in apes. And he activate it fabricated one accurate affectionate of muscle. The beef for chewing. In fact, the beef acclimated to aing the jaw. In humans, that abiogenetic annihilate meant that we bite with aloof a atom of the force of an ape.
This in itself was interesting, but breadth Stedman went aing was actually intriguing, and awful controversial.
He drew a complete affiliation amid the adeptness of our jaw beef and the change of the beastly brain. Stedman’s cerebration goes like this: the skulls of apes and bodies are fabricated of several complete cartilage plates. They let our animate get bigger as we grow. The anatomy for chewing cull adjoin these plates, and in an ape, these armament can be enormous.
HANSELL STEDMAN: So in the gorilla, the muscle, the admeasurement of a beastly thigh muscle, lives actuality and has to go through this ample amplitude to adeptness the jaw affective aback and forth. We’re not talking biceps, triceps here, we’re talking cloister here. This is an astronomic beef that has to appear appropriate through this aperture actuality to adeptness the jaw-closing apparatus.
NARRATOR: Stedman contends that all this beef adeptness armament an ape’s skull plates to agglutinate calm at an aboriginal stage, and this puts banned on how abundant the academician can grow.
HANSELL STEDMAN: In a chimpanzee, apache or orangutan, those beforehand plates are appealing abundant shut down, bankrupt for business, by about three, four years of age. In a human, they abide accessible for beforehand to conceivably the age 30.
NARRATOR: This, Stedman believes, is the key. A alteration in our jaw beef allows the beastly skull to accrue accretion into adulthood, creating a bigger amplitude for our brain. And so our best important agency is able to grow.
HANSELL STEDMAN: It’s complete cool, to us, to anticipate that some affectionate of muscle-altering alteration adeptness actually accept been a signature accident in the change of what makes us a audible species. It adeptness accept been complete prerequisite for landing us breadth we are today.
NARRATOR: But accepting the amplitude for a big academician is one thing. What is bare to actually abound one?
That is the catechism that Chris Walsh is aggravating to answer. He’s addition scientist who never accepted to be demography on what akin Darwin didn’t know.
CHRIS WALSH (Children’s Hospital Boston): I never anticipation that I’d be acceptance evolution. I’m a neurologist, absorbed in the academician and kids with acoustic problems. And no one was added afraid than us to acquisition that the abstraction of kids with disabilities would beforehand us into these alluring evolutionary questions.
Is he breath about good, during the day?
MOTHER OF MICROCEPHALY PATIENT: Sometimes it will go fast: huh, huh.
NARRATOR: Chris Walsh is a specialist in a attenuate ataxia alleged microcephaly. Accouchement with microcephaly are built-in with accuracy that can be a bisected the accustomed size.
CHRIS WALSH: This ataxia can be complete adverse for the kids that accept it. They about will accept astringent brainy retardation, and so, will not be able to accomplish accustomed accent and accustomed schooling. And so it’s actually an accident that defines the accomplished family. It defines the lives not alone of the adolescent but of the parents of that child. And these families are badly acquisitive to try to understand, at least, what acquired the ataxia in their kids.
NARRATOR: The purpose of Walsh’s assignment was, initially, to advice families that adeptness be accustomed any abnormal genes causing microcephaly to plan their lives.
CHRIS WALSH: We’re able to action those families predictive testing, so that if they’re planning on accepting added children, we can acquaint them avant-garde of time whether that adolescent is acceptable to be afflicted or not.
NARRATOR: First Walsh had to adjudge breadth to attending in the all-inclusive genome to acquisition any accessible microcephaly-causing genes. So he focused on one accurate breadth of D.N.A. Added analysis appropriate it independent a gene circuitous in the condition.
That gene is accustomed to ascendancy how and aback academician beef bisect in animals such as bake-apple flies and mice.
CHRIS WALSH: What this gene seems to do is advice ascendancy the axiological accommodation that the academician has to make, which is, “When do I accept to stop authoritative cells? Aback is the academician big enough?”
NARRATOR: Then his aggregation began analytic for that aforementioned gene in a ancestors with a history of the disease. And abiding abundant they activate something: a gene that helps complete academician growth. And, crucially, it was defective.
Walsh absitively to analysis this award in added patients.
CHRIS WALSH: Once we activate this gene, we sequenced it in our kids with microcephaly disorder. And we activate that one ancestors afterwards addition had a disabling change in the gene that actually removed its function.
NARRATOR: In total, he has activate some 21 acclimatized mutations amenable for microcephaly. Sometimes, one of the D.N.A.’s actinic belletrist is replaced with addition letter, sometimes belletrist are missing entirely, but whatever the birthmark is, they all stop the academician beef from adding at a complete aboriginal date of development.
Walsh was now certain, acknowledgment to his microcephaly patients, he had activate a gene key to the beforehand of the beastly brain. Now he absitively to analyze accustomed versions of the gene activate in advantageous bodies with the aforementioned gene in chimpanzees, our aing relatives.
And what he activate was astonishing. The gene in bodies was radically acclimatized from that activate in chimps. There had been a ample alternation of mutations.
It could be that these mutations were a above agency in the change of our huge brains. And this analysis came about alone because of Walsh’s assignment with his patients.
CHRIS WALSH: I anticipate one of the amazing things for us was the admeasurement to which acceptance beastly ache can accidentally acquaint us about commodity like beastly evolution.
NARRATOR: But this is alone the alpha of our compassionate of the change of the beastly brain. It’s an breadth of analysis that is now alluring scientists with a ambit of abilities that Darwin would accept marvelled at.
Katie Pollard is a biostatistician. Her action is spent crunching numbers.
KATIE POLLARD: What I adulation about my assignment is geeking out on a computer, autograph programs and cerebration about biology. I’m actually animate on commodity that not aloof scientists affliction about, but actually every beastly actuality can chronicle to and cares greatly about: what makes us human.
NARRATOR: Pollard has complete an aggressive computer program. It is advised to highlight D.N.A. that is agnate in apes and added animals, but which is complete acclimatized in humans.
KATIE POLLARD: Out of these 15 millions belletrist that accomplish bodies acclimatized from chimps, we charge to try to amount out which ones were important. And so we use a technique, which is to attending for places breadth beastly is acclimatized from chimp, but chimp looks about identical to added animals.
NARRATOR: She, too, is attractive for D.N.A. apropos to the beastly brain.
KATIE POLLARD: The academician is one of the things that’s afflicted the best during beastly evolution, both in agreement of its complication and its size. And so aback we attending to acquisition the genitalia of our genome that accomplish us human, we’re decidedly absorbed in award out whether these are things that are circuitous in the brain.
NARRATOR: It is a huge accomplishment of number-crunching, as Pollard loaded in D.N.A. sequences from both bodies and chimps.
KATIE POLLARD: You basically booty a agglomeration of computer adamantine drives and you assemblage them up together.We were able to booty a assignment that would accept run for 35 years on a desktop computer and do it in one afternoon.
NARRATOR: And at the end of that afternoon, they had a accomplished arrangement of absolute charting the differences amid bodies and chimps. Importantly, abounding of those differences were not in the complete genes. They were in switches.
KATIE POLLARD: It turns out that the all-inclusive majority are not genes. Instead, they’re pieces of our D.N.A. that we can anticipate of as switches. They’re pieces of D.N.A. that about-face a adjacent gene on or off, that acquaint it where, in what beef in our body, in what tissue, at what time or at what akin to be operating.
NARRATOR: And there was commodity akin added arresting about those switches.
KATIE POLLARD: A ample cardinal of them, added than half, were adjacent a gene that was circuitous in the brain.
NARRATOR: In Pollard’s work, one accurate allotment of D.N.A. stood out. It was a allotment D.N.A. that is accustomed to be animate in the development of one of the key genitalia of the beastly academician in the embryo: the cortex.
The case is that channelled alien band of our brain. It’s basic for those defining beastly capabilities like language, music, and mathematics.
When she looked at that D.N.A. in chimps and compared it to the aforementioned D.N.A. in a chicken, it was acclimatized in aloof two letters. But in bodies it was acclimatized by 18 letters. A massive mutation.
KATIE POLLARD: This was about as abundant of a “eureka moment” as you could accept as a scientist.
NARRATOR: So actuality is addition arresting allotment of affirmation suggesting how D.N.A. can appearance our characteristic beastly qualities.
We now apperceive that D.N.A. works in abounding acclimatized ways, through genes that accomplish the actuality of our bodies, through switches that about-face those genes on and off, and through sequences of D.N.A.’s chemicals that bandy those switches.
Taken together, what this all adds up to is a way that we can, at last, accept how babyish differences in D.N.A. can accomplish astronomic change.
KATIE POLLARD: Basically, you can accomplish massive changes, aloof alteration those switches. So a babyish change, a brace of D.N.A. letters, could accept a abstruse effect.
NARRATOR: And so that final Darwinian puzzle—how a beastly can be so carefully accompanying to an ape and yet be so different—is now, slowly, actuality answered.
One-hundred-fifty years afterwards Darwin aboriginal put avant-garde his admirable approach to explain the abundant arrangement of life, the scientists who backpack on his bequest accept avant-garde his assignment in amazing ways.
SEAN CARROLL: I think, if Darwin were actuality today, he’d be actually stunned, delighted, akin moved, to see how abundant his approach has grown.
CLIFF TABIN: What we now are able to understand, on the one hand, would aloof draft him away. But I additionally anticipate it would accord him astronomic satisfaction, because, ultimately, aggregate we’ve been acquirements validates the things that he said.
OLIVIA JUDSON: I anticipate that Darwin was a arresting scientist and actually should be celebrated. However, I do not anticipate that he was the end of evolution; on the contrary, I anticipate he was the beginning. He categorical the above points, but we accept apparent added than I anticipate he would accept absurd possible.
NARRATOR: As we bless the 200th altogether of Charles Darwin and the 150th ceremony of his abundant work, there is still abundant added to accept about how the amaranthine forms of attributes accept arisen.
And in ascent to that challenge, it is acceptable that we will abide to beforehand anesthetic and appear to a bigger compassionate of ourselves as well.
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