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The Evolution of Sex Documentary - Full HD Movie Uncut
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00:01Sex is a battlefield.
00:04Animals will go to every extreme to mate and ensure their survival.
00:09Without sex, a species is history.
00:13Its genes a dead end.
00:15From violent couplings, to sperm wars, to mating rituals,
00:20and finally, amazingly, to love.
00:25Sex drives evolution.
00:28And evolution drives sex.
00:32In nature, it really is all about sex.
00:37Just off the coast of Bimini Island in the Bahamas,
00:46scientists are studying a marvel of evolution.
00:55Over millions of years, evolution has built the protruding jaw and razor-sharp teeth of the ocean's master predator.
01:04But sharks are more than just killing machines.
01:14They are pioneers of sex.
01:27Half a billion years ago, sharks really invented what people would call sex.
01:33Sam Gruber has studied sharks for 45 years.
01:39People basically don't know much about sharks.
01:42And they think of them as the deaf fish from hell.
01:45But really, they're highly, highly sophisticated, tremendous animals.
01:49In addition to complex navigation and communication systems,
01:54sharks were one of the first to develop a whole new way to have sex.
01:58It may not look like very much, but it represents a huge evolutionary leap in reproductive behavior.
02:07If you look very closely, you'll see these two little finger-like projections, which are called claspers,
02:13are actually the penis of the male shark.
02:17400 million years ago, sharks became one of the first vertebrates to evolve a penis.
02:26But they were hardly the last.
02:32Over millions of years, the penis proved so valuable
02:36that it evolved independently in animals as different as insects, birds, and reptiles.
02:42The penis is a good example of convergent evolution because it serves one purpose,
02:48but it's arisen in many different ways in a variety of organisms.
02:51But how did the penis become so vital?
02:59700 million years ago, sharks, fish, and other vertebrates have yet to evolve.
03:05Sea life is instead comprised of simple, single-celled creatures.
03:11To pass on their genes, they don't have to partner up.
03:15They can reproduce by themselves.
03:18Reproduction before sex was all asexual.
03:23Asexual reproduction means that you just make copies of yourself and send them off into the environment.
03:28They have all of your genes and no one else's.
03:32Asexual reproduction does guarantee that 100% of an organism's genes are passed on.
03:41But on the evolutionary battlefield, this strategy has one serious flaw.
03:48When each and every creature shares the exact same genes, they also share the same genetic weak spots.
03:55Imagine that a virus shows up on the scene, and that virus attacks you if you have a very specific gene sequence in your DNA.
04:03Now, if everyone in your population has the same DNA, that means that that virus is going to wipe everyone out.
04:09But with sexual reproduction, the mixing and matching of genes increases the odds of at least some individuals living on.
04:23The secret to survival is sex.
04:26The first animals to adopt sexual reproduction emerged 600 million years ago.
04:34But the sex they practiced is not what humans might imagine.
04:39These passive creatures, relatives of modern coral, were tightly anchored to the sea floor.
04:45How can you mate when you can't move?
04:48Cast sperm and eggs on the waves and hope they meet.
04:54Each summer, billions of coral polyps simultaneously launch their reproductive cells into the current.
05:04Each coral releases both sperm and egg.
05:09But instead of combining with each other, they wait until they encounter the seeds of another coral.
05:15No one knows how they do it.
05:18This mass spawning is one of nature's most arresting spectacles.
05:23But it evolved as a matter of survival.
05:28Mass spawning by corals could be called a defense mechanism.
05:31Having all of the eggs and sperm released at the same time allows some of the offspring to survive even when there are predators around.
05:39You swamp the predators, you produce so many that they can't all be eaten by those predators at that point in time.
05:45For stationary animals, casting DNA into the ocean may have been the only way to sexually reproduce.
05:52But a new class of creatures was about to evolve, and sex would evolve with them.
05:58About 570 million years ago, in a very brief period of time, we see the origin of many different, often very complex body forms, some of which are still with us today.
06:14Many forms that resemble modern invertebrates, crustaceans. We even see the first fish.
06:19These early fish could move like no other creatures that came before.
06:26Instead of relying on ocean currents to carry their fate, males could directly target the females' eggs with their sperm.
06:33But even this method of mating had its pitfalls.
06:38The eggs, once fertilized, were not only tiny and fragile, they were exposed.
06:45This forced the parents to either stand guard or abandon them altogether.
06:49It would take another 200 million years for evolution to come up with a new plan, which is where sharks come in.
07:03In sharks, evolution gave rise to an innovation that allowed males to deploy sperm directly inside the females.
07:12Sharks invented sex, so to speak.
07:17This is just a huge difference from what we see in animals that lived a half a billion years ago.
07:25Instead of two fish just randomly spraying their eggs and sperms out into the water, helter-skelter, these animals have to actually come in contact.
07:35Sharks are one of the first vertebrates to physically connect during sex.
07:43It may sound friendly, but with sharks, it's anything but.
07:49Cute guys, right?
07:55The male will bite her pectoral fin, her arm fin, and roll her over.
08:02Then the male has these two claspers, or penii, and one is rotated around while the other stays back.
08:13And that's inserted into the female's cloaca, which is the common duct.
08:20This vertical hold may look brutal, but biologically speaking, it's a thing of beauty.
08:26It looks to me like a ballet, because they have very difficult tasks to go through to bring themselves together.
08:36Each seemingly violent act has a necessary sexual function.
08:42The male flips the female shark to her back to relax her for penile insertion.
08:46He sinks his teeth into her skin to trigger her ovulation.
08:52She's even protected from his gashing.
08:55Female sharks have skin twice as thick as male sharks.
08:59They have amazing healing properties.
09:02They can have huge lacerations, which would kill a human, and they're perfectly fine with it.
09:07But the crucial innovation of shark sex is the penis.
09:16Once the male is firmly attached, a spur at the appendage's tip prevents it from slipping out.
09:23A sack in the male's abdomen fills with seawater,
09:27and propels the sperm directly into the female's womb, where eggs await fertilization.
09:33So not only did they invent copulation, but they also invented getting pregnant.
09:41That is to say, internal fertilization.
09:44This represents a whole new stage in reproductive biology.
09:48Internal fertilization has been a foundation of sharks' 400 million year reign as the ocean's top predators.
09:55Not only does it protect their developing eggs from enemies, it leads to the birth of large, fully formed pups that are literally born to kill.
10:11For hundreds of millions of years, animals would remain confined to the Earth's oceans.
10:16Three hundred and seventy million years ago, a unique lineage of fish began to move towards land.
10:24Called tetrapods, they evolved legs from fins.
10:29In time, those legs became sturdy enough to let them move out of the water.
10:35But this new world presented new problems.
10:40If you look around today, there are creatures that spend all their time on land.
10:45But to do that, you have to have a whole lot of tricks.
10:48You have to be able to lay eggs or give birth to live young.
10:52If you are laying eggs, your eggs have to be waterproof.
10:55The fish ancestors of tetrapods simply dropped sperm into the current to fertilize eggs.
11:00But that wouldn't work on land.
11:04So one group of tetrapods, the ancestor of reptiles and mammals, successfully changed their method of reproduction.
11:13As sharks had before them, reptiles developed internal fertilization.
11:19And then, they went beyond, evolving an extraordinary adaptation to protect their young.
11:25The amniotic egg.
11:29This marvel of evolutionary engineering not only nourished the developing young within.
11:35Its hard shell kept the egg from drying out.
11:39The amniotic egg gave reptiles the ability to conquer land.
11:44Reproducing, spreading and growing on a whole different scale.
11:49And for the dinosaurs, this scale would be a big problem.
11:56When you're 40 feet long and weigh 6 tons, how do you do it?
12:06If you can't mate, if you can't pass on your genes, you are evolutionary history.
12:12But what happens if your own size gets in the way of mating?
12:23Some dinosaurs evolved to be the biggest animals ever to live on land.
12:33With dinosaurs like T-Rex topping out at more than 15 feet, sex gets complicated.
12:39And for all we know about dinosaurs, the details of their sex life remains a mystery.
12:47Imagine a 40-ton dinosaur trying to reproduce.
12:51Obviously, two of these behemoths would have had to get together.
12:55But exactly how they did so is still a huge question for paleontologists.
12:58Fossilized eggs are clear evidence that dinosaurs had intercourse and reproduced through internal fertilization like birds today.
13:11And the bones of dinosaurs are littered across all seven continents.
13:17Testament to creatures that dominated the earth for 160 million years.
13:22Clearly, these enormous animals must have evolved an extremely successful method of mating.
13:33Paleontologist Ken Carpenter has puzzled for years over the mystery of dinosaur reproduction.
13:39It's a whole process of trying to understand what dinosaurs were like as living animals.
13:47They had to have been able to reproduce in order to be so successful for over 200 million years.
13:52How did the males and females get together?
13:54What made Carpenter's investigation difficult was that all he had was bones.
13:59No reproductive organs have survived the fossil record.
14:05To discover what dinosaur sex might have been like, Carpenter turned to a creative mix of comparative anatomy,
14:13physics, and deduction.
14:17Starting with the dinosaur's reptile cousin, the crocodile.
14:23Male crocodiles have unique sex organs, not like the claspers of the shark, but not a penis as we humans know it either.
14:35Unlike humans, dogs, cats, they don't have this very long organ that sticks out all the time.
14:41It's actually a much smaller organ that's kept inside the body.
14:45Most of the time, the male's genitalia is kept inside a slit on his underbelly called the cloaca.
14:51During sex, however, muscles inside the cloaca contract, averting the animal's penis.
15:00Just three inches long in the 12-foot crocodile, the male must insert this tool into the female's cloaca to deposit his sperm.
15:10For creatures the size of dinosaurs, that would be like trying to stick a key in a lock by moving the whole building.
15:17Was it possible?
15:22To find the answer to that question, Carpenter turned to another present-day creature.
15:28One that shares the dinosaur's problem of how to fertilize an internal egg, despite its enormous size.
15:35The elephant.
15:40To reproduce, the male elephant rears up and leans on the female.
15:46But doing so puts a huge amount of weight on her back.
15:51Over time, this pressure causes permanent damage, creating small fractures in the female's backbones.
15:57If dinosaur sex took the same form, Carpenter should find similar fractures in their fossils.
16:07This vertebrae here comes from a duck-billed dinosaur.
16:12Possibly this breakage was due to the male climbing on top of a female during sex.
16:18Well, maybe.
16:20But we'd have to know what gender this vertebrae is.
16:24If it's a male, it would mean one male trying to mate with another male.
16:29Maybe that's why dinosaurs became extinct. I don't know.
16:31But the elephant-like rear mount posed a more fundamental problem.
16:40The male would have climbed up, put his weight on her back.
16:44Could her bones have supported it?
16:47Elephants weigh up to seven tons.
16:51But some dinosaurs weighed as much as 25 tons.
16:56Carpenter calculated the bone strength needed to withstand that much force.
17:01And concluded that it was too much.
17:04The elephant weigh was out.
17:10Undeterred, Carpenter retraced his steps to crocodiles and alligators.
17:16Creatures with a mating style that avoids load-bearing altogether.
17:21They've got the water to suspend them. It's almost like being in space.
17:25The male and females can basically rotate together.
17:27The male can stick his penis into the female's cloaca and interject sperm.
17:33So could dinosaurs have had sex under water?
17:37Carpenter consulted the charts.
17:39There were no huge bodies of water except in a very few places.
17:44Which would mean then that dinosaurs would have to traipse for sometimes literally thousands of miles in order to have sex.
17:51That's an awful lot of work just for sex.
17:55Another dead end.
17:57Birds were next.
17:58They are the direct descendants of dinosaurs and they lay eggs like dinosaurs.
18:04Could they copulate the same way?
18:07Birds do it basically as a bunch of quickies.
18:11Mostly because they're trying to fly at the same time as they're trying to reproduce.
18:15The males would be fluttering their arms as they're trying to get up against the female.
18:18Birds quick transfer of sperm known as a cloacal kiss would have its advantages for creatures as large as dinosaurs.
18:27But again, there are problems.
18:31Most dinosaurs don't have wings.
18:34And just as importantly, how could they do it with their massive armor in the way?
18:39The dinosaur's bony tail is heavy and rigid and not easily moved.
18:45The normal procedures of comparative anatomy had left Carpenter with a trail of false leads.
18:52Racking his brain for any idea that might work, Carpenter found one right at his feet.
19:00The household cat.
19:02And while cats are no more like dinosaurs than dogs or like lizards, Carpenter believes the cat's way would work for T-Rex.
19:17If the female lowers herself much like a cat, raises her rear end up, the tail would certainly go up in the air and would expose her sex organ to the male.
19:26And the male can then climb up there and grab her on her neck and then they can go at it.
19:32In the feline position, with the female's head lowered and tail lifted, the problem of the male's enormous weight would be lifted off the female's back.
19:43At the same time, the position would allow easy access for the male.
19:48Carpenter's theory is the first to offer a workable answer to the mystery of dinosaur sex.
19:54And the first to explain how dinosaurs were able to reproduce their way into history as the unrivaled rulers of Earth for 160 million years.
20:09Dinosaurs were the largest animals to mate on land.
20:14Insects are some of the smallest.
20:16And in their tiny world, sex is a war story that's been going on for millions of years with its own villains and heroes.
20:27You know, when it comes to looking at reproductive biology, you've got to say that cockroaches are a superstar.
20:3265 million years ago, an asteroid six miles wide hurdles down from the sky and smashes into the Gulf of Mexico.
20:49The impact signals the end of the dinosaur age.
20:57Their extinction claims half of all species turning the Earth into a wasteland.
21:04But insects endure.
21:06How insects out-survived so many other animals is still a mystery.
21:15Some scientists believe the asteroid's impact caused a temperature shift that put insects into hibernation.
21:22When they re-emerged, they flourished, developing new ways to reproduce at staggering rates.
21:33But in the insect world, sex is more than just reproducing.
21:38It's a battle of the sexes, a war over sperm.
21:42Sperm competition has been extremely important in the evolution and diversification of insects.
21:49Males are, of course, competing to make sure their sperm makes it into the female reproductive tract.
21:56At the same time, females are able to manipulate which sperm make it to successfully fertilize the egg.
22:03The female seeks multiple sexual partners, giving her offspring a diverse genetic portfolio and a greater chance at survival.
22:16But the male seeks to father all the offspring.
22:20The more paternity, the better the chances for his genes.
22:23What the male wants and the female needs are in conflict and has spawned an evolutionary arms race, stretching the limits of evolution.
22:38A far cry from the shark's simple clasper, insects have evolved the widest variety of penis shapes on the planet.
22:46In one of the most shocking, the male damselfly's penis has sharp horns at the tip and spiky thorns down the side.
22:57If it looks like a scrub brush, there's a reason.
23:01The male uses his tool to scrape out the sperm of his rivals before depositing his own.
23:07This technique removes more than 90% of the existing sperm, virtually guaranteeing the offspring will be his.
23:16And the males of other insect species take even greater pains to guarantee a return on their deposit.
23:23There's a great strategy that some insects and also some mammals have come up with, which is called a copulatory plug.
23:30And after a male mates with a female, some of the semen hardens and becomes a plug.
23:35And it prevents other males from being able to mate with the female. It's a pretty good strategy.
23:38But honey bees take it a step further, not just using a plug. They are the plug.
23:46Tens of thousands of male bees compete for the queen. Only one gets to mate with her.
23:52Think he's the lucky one? Think again.
23:54Upon reaching climax, his penis rips away from his body and becomes stuck inside the queen.
24:04He dies in order to lock his sperm inside her.
24:08But despite this ultimate sacrifice, female bees evolved a countermeasure, a way to pop out the plug.
24:15Freeing the female to choose the sperm of another, maybe better mate.
24:21In bees at least, females are winning the sexual arms race.
24:26But in other species, the males are taking the lead.
24:31In stick insects, males have gone beyond the removable plug, evolving into living chastity belts.
24:38They attach to their mates for weeks to prevent any other male from fertilizing her eggs.
24:46And the male love bug takes this strategy a radical step further.
24:53Once he locks his sex organ inside his partner's, he throws away the key.
24:59The male's commitment to the act is total.
25:03Once joined, he spends the rest of his life in the act of copulation.
25:06After the couple is through mating, he will die to be dragged around by the female until she lays her eggs.
25:15Eggs all fathered by that single male.
25:19From species to species, the sexual arms race is ongoing throughout the insect world.
25:26But in one familiar group, females may have found a way to finally end the war.
25:32Entomologist Ron Harrison heads up the cockroach extermination lab at the Orkin Training Center in Atlanta.
25:41To come up with ways to kill these ultimate survivors, Harrison spends his days studying the species most commonly found in homes.
25:50Ninety-five percent of all cockroach problems in urban situations are German cockroaches.
25:56They're very quick in their reproductive abilities, and therefore that helps them become resistant to products that we actually use to try to get rid of them.
26:03Evolution has provided cockroaches a host of traits that make them almost impossible to eliminate.
26:11They can live a month without food and last hours without oxygen.
26:19But most critical to their survival is their speed of reproduction.
26:24A quality that might indicate that cockroaches have sex all the time, except they don't.
26:30Once a female has had sex and has that sperm, she's able there to hold it and then fertilize as she needs, rather than have to have sex again.
26:41Because of this one adaptation, the female needs to mate only once to remain pregnant for the rest of her life.
26:52Her one act of sex can yield hundreds of thousands of offspring, a remarkable ratio.
26:58This benefits the female in more ways than one.
27:01Mating in itself is costly. The more a female mates, the lower her probability of survival.
27:08Perhaps because there's some damage that occurs, they might be at risk of predation.
27:13And there's even some seminal fluids that carry toxins that decrease female survival.
27:20After her one act of sex, the female carries fertilized eggs with her throughout her entire life.
27:25So every female in the colony has the potential to become a colony herself.
27:34In pest control, what's really scary to us then is if you happen to have a German cockroach in the cuff of your pants,
27:41or in your pocket, or in a box that comes from the grocery store, and it happens to be a pregnant female,
27:46that's all that's needed to get an entire population going.
27:49This adaptation has given the species the ultimate survival advantage.
27:57When you look at the whole evolution of animals, these started out 400 million years ago,
28:03and are continuing to be very successful.
28:06You know, when it comes to looking at reproductive biology, you've got to say that cockroaches are a superstar.
28:10The battle of the sexes has made cockroaches, together with the rest of the insects, the most diverse group of animals on earth.
28:21The drive to reproduce shapes not only insect life, but mammals as well, including us.
28:29Everywhere in the natural world, sex gets everyone bent out of shape.
28:34Animals will do anything to me.
28:46The drive to pass on genes and ensure survival of the species is so strong that it causes evolutionary changes.
28:55This process is called sexual selection.
28:58It's a type of natural selection, but it's the kind of selection for the kind of traits that evolved not to survive another day, but to win at the mating game.
29:09To be successful, in evolutionary terms, your genes have to be in the next generation.
29:15As soon as you have sexual reproduction, what you're doing is going out into the environment and looking for other individuals that are doing well,
29:22and trying to get some of their genes into your offspring.
29:24You need to assess how everybody in your population is doing in terms of their reproductive output.
29:30The game of courtship in the animal kingdom is largely typecast.
29:35For the most part, males display. Females choose.
29:41There's not an animal on this planet, in the wild, that will copulate with anybody.
29:46They all have favorites. Too old, too young, too scruffy, too stupid acting, and they won't do it.
29:53And for good reason, because an animal only has a few chances to pass their DNA on into tomorrow.
30:01And so they want to do it with the kind of individual that will really enable them to survive.
30:08And females can often have really weird criteria by which they choose which male they're going to mate with.
30:12Sexual selection has had huge consequences. Males of a species, they have to compete with each other to find a female,
30:19gives rise to a whole different set of behaviors and appearances in animals that compete with other males and try to get a female mate.
30:25For example, a moose uses its antlers to fight other moose in order to win the opportunity to copulate with certain females.
30:33So there's two types of traits that evolve for sexual selection. One are traits simply to fight off members of your own gender,
30:42and others are traits to attract the opposite sex.
30:46The pressures of sexual selection worked on the male stock-eyed fly to compete for the largest eye stalk,
30:52on the male finch to sing and to show red,
30:59on the rhinoceros beetle to grow massive fighting horns,
31:05on the male lion to grow his mane,
31:09and on the male giraffe to grow a powerful long neck.
31:13Some forms of sexual selection can actually drive species extinct,
31:20because the traits that females prefer are so elaborate that they actually get in the way of day-to-day lives of males.
31:26Take the case of the Irish elk, the ancient cousin of Europe's fallow deer.
31:36Females really liked big antlers, and so over time males with large antlers were selected over males with smaller antlers.
31:43Over progressive generations the average size of antlers in the population got bigger and bigger and bigger and bigger.
31:49Eventually the antlers got so big that they were at the very limit of what an animal can sustain and still survive in its environment.
31:56And ultimately the Irish elk went extinct, and a lot of people think that it went extinct because its antlers were just too big.
32:03But even after the rams have butt heads, and the mating has begun,
32:09in some species the female has more work to do to be sure that goods are delivered.
32:18The female or the male approach each other, then the male mounts the female.
32:23After one, two seconds the female starts calling.
32:30German primatologist Donna Pfefferle works with a unique group of wild macaques who live atop the rock of Gibraltar.
32:37She came here to investigate the mystery of why female macaques cry out so loudly during sex.
32:45Over two mating seasons she recorded the macaques.
32:51Focusing on the frequency and intensity of the female's cries.
32:56She then looked for differences between the females who made noise and the females who didn't.
33:05What she found was extraordinary.
33:08Far more of the noisy females became pregnant.
33:11The earlier, the faster, and with the higher peak fingers the female calls, the more likely the male is to ejaculate.
33:22In fact, males were ten times more likely to ejaculate with a calling female than with a silent one.
33:30Fefferle concluded that the females evolved the loud sex noises in a clear case of sexual selection.
33:40The noises increased the odds of burying young.
33:43They're screaming and shouting for a reason.
33:49If he doesn't ejaculate, then what's going to happen is she's not going to conceive.
33:54So what she's got to do is she's got to encourage him.
33:57Eric Shaw has spent years closely observing the Gibraltar macaques, who are known for one thing, sex.
34:08They have sex on average once an hour.
34:16And they have evolved to use it for social purposes.
34:22Kevin.
34:25We've got free-ranging primates here that we know have been here for 300 years.
34:31I know, I know, I know. Stop panicking.
34:33There's a lot of questions that they can answer for us, be it a question of how to feed them, or be it a question of sex.
34:42For these primates, sex is part of how the community communicates and bonds.
34:46They use their sexuality in a lot of ways, like we do, I suppose.
34:52You're a male and a female here, and he threatened her, because you're a little bit too close to my food.
34:58To stop the threat, she presents herself. In other words, take me, I'm yours.
35:03Here we go.
35:06Here we go.
35:14That was sheer total submission and passiveness.
35:19She presented herself, I'm not a threat.
35:22He decided to go all the way this time and accept her submission.
35:27And now there's peace in the world.
35:28The macaque community needs order to keep their elaborate social network intact.
35:34There are little families within families, you know, one female will have five children over here, another will have four over there.
35:40But they need this protection, they need this cohesion, they need to move as a troop.
35:44With primates like macaques, sex moves beyond its primary function and is put to many different uses.
35:52The scientists call these behaviors sexual currency.
35:55Primates have developed sexual reproduction to an elaborate art.
36:00No longer is it just a physical coming together with no consequences other than reproduction.
36:06Now it's the fulcrum of many different aspects of primate societies.
36:11A lot of the primates will exchange food for sex, express power with their sexuality, express friendship with their sexuality.
36:19Sex is a very powerful exchange mechanism.
36:22The mix of sex for reproduction and social purposes evolved by primates like the macaque set the stage for the human sexuality that was to come.
36:33Humans would add one more most unusual layer to the evolution of sex.
36:41Human beings began to emerge as distinct from our primate cousins just a few million years ago.
36:47When our ancestors came down out of the trees and began to stand up on two feet instead of four, they also changed some of their sexual anatomy.
36:57Helen Fisher studies the evolution of human sex.
37:00The female vaginal canal is no longer tipped backwards the way it is among chimpanzees.
37:07It evolved to move somewhat forward, probably for easier access during the missionary position.
37:12As the female's anatomy changed, so did the male's.
37:18The penis had to reach deeper into the female's body.
37:22So it evolved to become significantly larger.
37:26Today, humans have the biggest penis of any primate.
37:31And the most highly developed, brain.
37:35I think that human beings made their biggest leap in terms of sexuality with the evolution of the brain.
37:43Over time, the human brain grew large.
37:47So large that its hard skull became a threat to successful reproduction.
37:51At some point during human evolution, we began not only to stand up on two feet instead of four, but the brain got to be too large for the birth canal.
38:02At that point, women began to have to bear their babies sooner so that they could get out of the birth canal.
38:06No one knows how long the first human mothers carried their young.
38:14But we do know that today, a 21 month pregnancy would be necessary for a human baby to be born as fully developed as a newborn chimp.
38:25With every human born essentially premature, family bonds became a necessity for survival of the species.
38:32And that necessity, argues Fisher, explains the mystery of love.
38:38As we evolved babies that would have a very long childhood and even adolescence, we began to need to sustain a partnership with somebody long term.
38:51And thus we see the evolution of these romantic love and deep attachment to a partner.
38:56Fisher studies the specific areas of the brain involved in sex and love.
39:05Inside an MRI machine, subjects are directed to think about their lover by looking at his or her photograph.
39:14As they do, their MRI lights up with regions of intense activity.
39:19An entire brain system devoted to love.
39:27By two million years ago, we began to build this very large cortex.
39:33And then suddenly sex and mind became interconnected.
39:39These brain systems for the sex drive and for romantic love are woven deep into primitive parts of the human brain.
39:45Humans forever changed sex with the evolution of love.
39:51And now, humans are going a step further, taking our evolution into our own hands and separating it from the act of sex.
40:04Sex has become futuristic.
40:08There's all kinds of ways now to basically bypass sex.
40:12We can clone individuals in a petri dish.
40:15There's all sorts of ways to fertilize individuals without engaging in intercourse.
40:19What is occurring today is that biology is beginning to manipulate those processes to alter its own self and to take control of its own future evolution.
40:35So it's becoming a very conscious thing.
40:38And 100 years, 200 years from now as we move forward, the process of human evolution is going to be directed by human choice.
40:46Gregory Stock is a biophysicist and the author of a book entitled Redesigning Humans.
40:54He is an advocate of human genetic engineering.
40:58And I could see a time when it's viewed as just kind of careless to conceive of children by the old ways, where it's just some random meeting of egg and sperm.
41:10How could you be so careless about something as important as a child?
41:16Stock believes the logical first step will be genetic screening.
41:21A process in which couples will be able to bring their sperm and egg together in the lab to generate multiple embryos.
41:29Then pick the one with the most desirable traits.
41:33So I think it'll be the parents will make choices about their children that are a little bit different from themselves, but really resonate with their own personalities.
41:44If they're really outgoing, they'll want children that are outgoing.
41:48If they're really conscious about their own intelligence, they'll choose kids that have a little leg up in that realm.
41:54If they're really athletic, they're going to want an athlete.
41:58And I see an enormous diversity as we go out into the future.
42:03We already are living in the age of engineered reproduction.
42:07The first so-called test tube baby is now in her 30s.
42:14Successfully cloned animals include the mouse, sheep, cattle, cat, horse, and chimp.
42:24Theoretically, the technology to clone humans exists, but hasn't yet been used.
42:30For stock, a future of engineered humanity would simply be a new phase in evolution.
42:38Consciousness having evolved to the point where it can chart its own future.
42:44As you begin to have meaningful choices, things that can be done that people consider to be of value.
42:51For instance, a genetic screening so that you can be absolutely certain that your child is going to be very, very healthy.
42:57Then I think you're going to get these technologies used in a very, very broad fashion.
43:02Natural selection has made some bad choices in the past.
43:07An awful lot of people have very bad backs.
43:10They've got bad shoulders.
43:12They pull out various parts of the body because it's not yet perfectly evolved.
43:17And if we could make some changes in selection so that we get rid of genetic diseases, it would be an improvement.
43:22As humans move to take the reins of their own reproductive evolution, a vital debate has begun.
43:31Genetic engineering in humans is a very risky activity.
43:35The problem is that by introducing variation, we might not know what all the consequences will be.
43:40We may insert a gene that we think causes one effect, but in fact it will cause other effects and disrupt the normal functioning of our chromosomes.
43:50Of course there are going to be problems.
43:55There are always problems with using technology, especially potent technology.
43:58But that doesn't mean we shouldn't go there.
44:04It's going to be a very messy, a very chaotic, a very unpredictable process.
44:10And to me, it's just the next stage of evolution.
44:13Taken to its logical extreme, in the future, the act of sex may have no place in human life at all.
44:24But for most scientists, the thought that the human animal would drop a behavior that is the product of millions of years of evolution is highly remote.
44:33Genetic engineering is far from the end of sexual reproduction.
44:39We are far from evolving beyond sex.
44:42I don't think that's ever going to happen.
44:45As long as there is life, it seems there will be sex.
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