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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, scientists are studying a marvel of evolution.
00:51Over millions of years, evolution has built the protruding jaw and razor-sharp teeth of the ocean's master predator.
01:05But sharks are more than just killing machines.
01:19They are pioneers of sex.
01:28Half a billion years ago, sharks really invented what people would call sex.
01:34Sam 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, sharks were one of the first to develop a whole new way to have sex.
01:59It 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, are actually the penis of the male shark.
02:18400 million years ago, sharks became one of the first vertebrates to evolve a penis.
02:24But they were hardly the last.
02:32Over millions of years, the penis proved so valuable that it evolved independently in animals as different as insects, birds, and reptiles.
02:43The penis is a good example of convergent evolution because it serves one purpose, but it's arisen in many different ways in a variety of organisms.
02:52But how did the penis become so vital?
02:59700 million years ago, sharks, fish, and other vertebrates have yet to evolve.
03:07Sea life is instead comprised of simple, single-celled creatures.
03:12To pass on their genes, they don't have to partner up.
03:16They can reproduce by themselves.
03:18Reproduction before sex was all asexual.
03:24Asexual reproduction means that you just make copies of yourself and send them off into the environment.
03:29They have all of your genes and no one else's.
03:33Asexual reproduction does guarantee that 100% of an organism's genes are passed on.
03:39But 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.
03:56Imagine that a virus shows up on the scene, and that virus attacks you if you have a very specific gene sequence in your DNA.
04:02Now, 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.
04:21The secret to survival is sex.
04:25The 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?
04:49Cast sperm and eggs on the waves and hope they meet.
04:56Each summer, billions of coral polyps simultaneously launch their reproductive cells into the current.
05:04Each coral releases both sperm and egg.
05:08But 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.
05:27Mass spawning by corals could be called a defense mechanism.
05:31Having all 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.
05:51But a new class of creatures was about to evolve and sex would evolve with them.
06:02About 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.
06:13Many forms that resemble modern invertebrates, crustaceans, we even see the first fish.
06:21These 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.
06:34But even this method of mating had its pitfalls.
06:37The 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.
06:50It would take another 200 million years for evolution to come up with a new plan, which is where sharks come in.
07:01In sharks, evolution gave rise to an innovation that allowed males to deploy sperm directly inside the females.
07:14Sharks invented sex, so to speak.
07:18This is just a huge difference from what we see in animals that lived a half a billion years ago.
07:24Instead of two fish just randomly spraying their eggs and sperms out into the water, helter-skelter, these animals have to actually come in contact.
07:36Sharks are one of the first vertebrates to physically connect during sex.
07:42It may sound friendly, but with sharks, it's anything but.
07:53Cute guys, right?
07:55The male will bite her pectoral fin, her arm fin, and roll her over.
08:01Then the male has these two claspers, or a penii, and one is rotated around while the other stays back, and that's inserted into the female's cloaca, which is the common duct.
08:17This vertical hold may look brutal, but biologically speaking, it's a thing of beauty.
08:27It looks to me like a ballet, because they have very difficult tasks to go through to bring themselves together.
08:35Each seemingly violent act has a necessary sexual function.
08:42The male flips the female shark to her back to relax her for penile insertion.
08:48He 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.
09:10But the crucial innovation of shark sex is the penis.
09:17Once the male is firmly attached, a spur at the appendage's tip prevents it from slipping out.
09:22A sac in the male's abdomen fills with seawater, and propels the sperm directly into the female's womb, where eggs await fertilization.
09:35So 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.
09:47Internal fertilization has been a foundation of sharks' 400 million year reign as the ocean's top predators.
09:58Not only does it protect their developing eggs from enemies,
10:02it 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.
10:18Three hundred and seventy million years ago, a unique lineage of fish began to move towards land.
10:25Called tetrapods, they evolved legs from fins.
10:30In time, those legs became sturdy enough to let them move out of the water.
10:38But 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.
10:54The fish ancestors of tetrapods simply dropped sperm into the current to fertilize eggs.
11:01But that wouldn't work on land.
11:05So one group of tetrapods, the ancestor of reptiles and mammals,
11:10successfully changed their method of reproduction.
11:13As sharks had before them, reptiles developed internal fertilization.
11:17And then, they went beyond, evolving an extraordinary adaptation to protect their young.
11:26The 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.
11:38The amniotic egg gave reptiles the ability to conquer land.
11:44Reproducing, spreading, and growing.
11:47On a whole different scale.
11:50And 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?
12:01If you can't mate, if you can't pass on your genes, you are evolutionary history.
12:16But what happens if your own size gets in the way of mating?
12:22Some dinosaurs evolved to be the biggest animals ever to live on land.
12:27With dinosaurs like T-Rex topping out at more than 15 feet, sex gets complicated.
12:40And 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.
12:54But exactly how they did so is still a huge question for paleontologists.
13:02Fossilized eggs are clear evidence that dinosaurs had intercourse
13:07and reproduced through internal fertilization like birds today.
13:13And the bones of dinosaurs are littered across all seven continents.
13:16Testament to creatures that dominated the earth for 160 million years.
13:24Clearly, these enormous animals must have evolved an extremely successful method of mating.
13:34Paleontologist 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,
14:09Carpenter turned to a creative mix of comparative anatomy,
14:14physics and deduction.
14:17Starting with the dinosaur's reptile cousin,
14:19the crocodile.
14:24Male crocodiles have unique sex organs.
14:29Not like the claspers of the shark.
14:32But not a penis as we humans know it either.
14:35Unlike humans, dogs, cats,
14:38they 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.
14:44Most of the time, the male's genitalia is kept inside a slit on his underbelly called the cloaca.
14:52During sex, however, muscles inside the cloaca contract,
14:58averting the animal's penis.
15:00Just three inches long in the 12-foot crocodile,
15:04the male must insert this tool into the female's cloaca to deposit his sperm.
15:08For creatures the size of dinosaurs,
15:13that would be like trying to stick a key in a lock by moving the whole building.
15:21Was it possible?
15:23To find the answer to that question,
15:26Carpenter turned to another present-day creature.
15:29One that shares the dinosaur's problem of how to fertilize an internal egg,
15:35despite its enormous size.
15:36The 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,
15:55creating small fractures in the female's backbones.
15:59If dinosaur sex took the same form,
16:02Carpenter should find similar fractures in their fossils.
16:06This 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.
16:17Well, maybe.
16:18But 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.
16:28Maybe 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?
16:46Elephants weigh up to seven tons.
16:50But some dinosaurs weighed as much as 25 tons.
16:55Carpenter calculated the bone strength needed to withstand that much force.
17:01And concluded that it was too much.
17:04The elephant weigh was out.
17:09Undeterred, Carpenter retraced his steps to crocodiles and alligators.
17:14Creatures with a mating style that avoids load-bearing altogether.
17:20They've got the water to suspend them.
17:23It's almost like being in space.
17:25The male and females can basically rotate together.
17:28The 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.
17:59They are the direct descendants of dinosaurs and they lay eggs like dinosaurs.
18:03Could they copulate the same way?
18:06Birds do it basically as a bunch of quickies, mostly because they're trying to fly at the same time as they're trying to reproduce.
18:14The males would be fluttering their arms as they're trying to get up against the female.
18:19Birds' quick transfer of sperm, known as a cloacal kiss, would have its advantages for creatures as large as dinosaurs.
18:26But again, there are problems.
18:30Most dinosaurs don't have wings.
18:33And just as importantly, how could they do it with their massive armor in the way?
18:40The 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.
18:51Racking his brain for any idea that might work, Carpenter found one right at his feet.
19:01The household cat.
19:06And while cats are no more like dinosaurs than dogs or like lizards, Carpenter believes the cat's way would work for T-Rex.
19:15If 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.
19:31In 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.
19:42At the same time, the position would allow easy access for the male.
19:47Carpenter'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.
20:05Dinosaurs were the largest animals to mate on land. Insects are some of the smallest. And in their tiny world, sex is a war story that's been going on for millions of years with its own villains and heroes.
20:26You know, when it comes to looking at reproductive biology, you've got to say that cockroaches are a superstar.
20:3965 million years ago, an asteroid six miles wide hurtles down from the sky and smashes into the Gulf of Mexico.
20:49The impact signals the end of the dinosaur age. Their extinction claims half of all species, turning the Earth into a wasteland.
21:04But insects endure.
21:09How insects out survived so many other animals is still a mystery.
21:14Some scientists believe the asteroid's impact caused a temperature shift that put insects into hibernation.
21:24When they re-emerged, they flourished, developing new ways to reproduce at staggering rates.
21:34But 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.
21:55At the same time, females are able to manipulate which sperm make it to successfully fertilize the egg.
22:02The female seeks multiple sexual partners, giving her offspring a diverse genetic portfolio and a greater chance at survival.
22:13But the male seeks to father all the offspring. The more paternity, the better the chances for his genes.
22:20What the male wants and the female needs are in conflict and has spawned an evolutionary arms race, stretching the limits of evolution.
22:36A far cry from the shark's simple clasper, insects have evolved the widest variety of penis shapes on the planet.
22:45In one of the most shocking, the male damselfly's penis has sharp horns at the tip and spiky thorns down the side.
22:54If it looks like a scrub brush, there's a reason. The male uses his tool to scrape out the sperm of his rivals before depositing his own.
23:06This 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.
23:29After a male mates with a female, some of the semen hardens and becomes a plug, and it prevents other males from being able to mate with the female.
23:36It's a pretty good strategy.
23:39But honeybees 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.
24:16Freeing the female to choose the sperm of another, maybe better mate.
24:20In 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.
24:39They attach to their mates for weeks to prevent any other male from fertilizing her eggs.
24:45And the male love bug takes this strategy a radical step further.
24:52Once 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.
25:25But 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.
25:49Ninety-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.
26:06Evolution has provided cockroaches a host of traits that make them almost impossible to eliminate.
26:12They 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.
26:31Once a female has had sex and has that sperm, she's able there to hold it and then fertilize as she needs,
26:38rather than have to have sex again.
26:44Because of this one adaptation, the female needs to mate only once to remain pregnant for the rest of her life.
26:51Her 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,
27:44and it happens to be a pregnant female, that's all that's needed to get an entire population going.
27:49This adaptation has given the species the ultimate survival advantage.
27:54When you look at the whole evolution of animals, these started out 400 million years ago,
28:02and are continuing to be very successful.
28:05You 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.
29:47They all have favorites. Too old, too young, too scruffy, too stupid acting, and they won't do it.
29:52And for good reason, because an animal only has a few chances to pass their DNA on into tomorrow.
30:00And 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.
30:34So there's two types of traits that evolve for sexual selection.
30:38One are traits simply to fight off members of your own gender, and others are traits to attract the opposite sex.
30:45The pressures of sexual selection worked on the male stock-eyed fly to compete for the largest eye stalk.
30:55On the male finch to sing and to show red.
31:01On the rhinoceros beetle to grow massive fighting horns.
31:04On the male lion to grow his mane.
31:09And on the male giraffe to grow a powerful long neck.
31:15Some 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.
32:17The female or the male approach each other, then the male mounts the female.
32:22After one, two seconds the female starts calling.
32:31German 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.
32:46Over 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 frequencies the female calls, the more likely the male is to ejaculate.
33:21In 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 bearing 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.
34:00Eric Shaw has spent years closely observing the Gibraltar macaques who are known for one thing.
34:08Sex.
34:09They have sex on average once an hour.
34:16And they have evolved to use it for social purposes.
34:22Kevin.
34:26We'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.
34:35It'll be the question of how to feed them.
34:38There'll be the question of sex.
34:42For these primates, sex is part of how the community communicates and bonds.
34:47They use their sexuality in a lot of ways, like we do, I suppose.
34:52The male and the female here, and he threatened her.
34:55Because you're a little bit too close to my food.
34:58To stop the threat, she presents herself.
35:01In other words, take me, I'm yours.
35:06Here we go.
35:07That was sheer total submission and passiveness.
35:18She presented herself, I'm not a threat.
35:21He decided to go all the way this time and accept her submission.
35:26And 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.
35:35You know, one female will have five children over here.
35:38Another will have four over there.
35:40But they need this protection.
35:41They need this cohesion.
35:43They need to move as a troop.
35:45With primates like macaques, sex moves beyond its primary function
35:49and 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,
36:17express friendship with their sexuality.
36:20Sex is a very powerful exchange mechanism.
36:23The mix of sex for reproduction and social purposes evolved by primates like the macaque
36:29set the stage for the human sexuality that was to come.
36:33Humans would add one more most unusual layer to the evolution of sex.
36:42Human 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,
36:54they 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.
37:06It evolved to move somewhat forward, probably for easier access during the missionary position.
37:12As the female's anatomy changed, so did the males.
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.
37:30And the most highly developed brain.
37:36I think the 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,
37:59but 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.
38:07No one knows how long the first human mothers carried their young.
38:11But 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.
38:24With every human born essentially premature, family bonds became a necessity for survival of the species.
38:31And that necessity, argues Fisher, explains the mystery of love.
38:41As we evolved babies that would have a very long childhood and even adolescence,
38:46we 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.
39:29By two million years ago, we began to build this very large cortex.
39:34And 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.
39:46Humans forever changed sex with the evolution of love.
39:51And now, humans are going a step further.
39:57Taking our evolution into our own hands.
40:01And separating it from the act of sex.
40:05Sex has become futuristic.
40:07There'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.
40:20What 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.
40:33So it's becoming a very conscious thing.
40:37And 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.
40:53He is an advocate of human genetic engineering.
40:59And I could see a time when it's viewed as just kind of careless to conceive of children by the old ways.
41:08Where it's just some random meeting of egg and sperm.
41:12How 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.
41:30Then pick the one with the most desirable traits.
41:34So I think it will be the parents will make choices about their children that are a little bit different from themselves.
41:41But really resonate with their own personalities.
41:43If 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.
41:55If they're really athletic, they're going to want an athlete.
41:59And 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.
42:29For stock, a future of engineered humanity would simply be a new phase in evolution.
42:37Consciousness having evolved to the point where it can chart its own future.
42:42As you begin to have meaningful choices, things that can be done that people consider to be a 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.
43:01Natural 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.
43:16And 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.
43:41We 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.
43:59But 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.
44:46As long as there is life, it seems there will be sex.
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