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Origins of Us
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00:05The shape of your face, walking on two legs, the way you see the world, what makes you the person
00:17you are? The story of each and every one of us can be traced back millions of years to the
00:28plains of ancient Africa. The answers to the question, what makes us human, lie buried
00:37in the ground, in the fossils and other traces of our ancestors, but also lie deep within
00:44our own bodies, in our bones, flesh and genes. As an anatomist, I'm fascinated by the way
00:54our bodies have been sculpted by our ancestors' struggle for survival.
01:06And what took us out of the forests, leaving the other apes behind, to spread out across
01:13the globe, was our search for food. It's got duty. It's left its mark in our mouths, and
01:24in our behaviour. Flames. Food makes us behave in the strangest ways. It's even driven the
01:34way we attract the opposite sex. The ways in which we find food and digest it have not
01:44only left their mark on our bodies, but underpin our success as a species.
01:50Flames.
01:51Oh, my God.
02:19The villagers off the coast of East Africa are home to an extraordinary creature.
02:27A link to our evolutionary past.
02:36This strange-looking animal is known as a tunicate or sea squirt.
02:41And believe it or not, this is a distant relative of mine.
02:57It is quite hard to believe I've got anything at all in common with this sea squirt.
03:01It doesn't have eyes, it doesn't have arms and legs.
03:04In fact, pretty much all it does have is a gut.
03:08He's got an in-hole to the gut there.
03:12There's an out-hole over there, it's a little U-shaped gut.
03:16This simple process of food in, waste out gives us the blueprint for the guts that lie at the heart
03:23of every animal, including us.
03:27We humans like to think that we are so special, that we are so different from every other life form.
03:34And yet, there is something that unites us with every other animal on the planet, and that is the search
03:41for food.
03:45And the quest to feed ourselves has driven changes in our bodies.
03:51The need for food hasn't just shaped sea squirts, it's shaped us as well.
03:57From our own guts to the way we move, the way we behave, and even the way in which we
04:03experience the world around us.
04:17But it's on land, here in Africa, that our story really begins.
04:24Over millions of years, our ancestors' bodies were shaped by the search for food.
04:30As they crawled out onto land, evolving into reptiles, mammals, and eventually, monkeys.
04:44They are fast asleep.
04:47These are red-collar-bust monkeys.
04:5030 million years ago, there weren't any humans on the planet, there weren't any apes, but there were monkeys.
05:13You and I evolved from monkeys, which would have looked something like this.
05:20Procleopithecus, an ancient primate ancestor, that lived in the trees on a diet of fruit and leaves.
05:30And their search for food has directly affected the way we see the world today.
05:39Most mammals wouldn't be able to tell the difference between these two tomatoes.
05:45But for you and me, the difference is obvious.
05:49And this is all because of a crucial change in our ancestors' eyes that probably happened 30 to 40 million
05:56years ago.
06:01At the back of all mammals' eyes are light-sensitive colour receptors called cones.
06:08Most mammals have only two types that cover the blue and yellow parts of the spectrum.
06:16But 30 million years ago, a genetic mutation created a third.
06:22One that opened up a whole new range of colour.
06:32Reds and greens.
06:41And with this, our full colour vision was born.
06:48Revealing a rich and bountiful range of foods.
06:58If you're a leaf-eating primate, three colour receptors might help you pick out the slightly paler, more yellow, tender
07:05leaves to eat.
07:06But for a fruit-eating primate, it means that you can pick up on the signals that the trees are
07:11giving you.
07:12That when something is ready to eat, it turns red.
07:16And you know that it is full of sugar and more nutritious.
07:30Being able to tell when fruit was ripe, packed with life-giving sugar and energy,
07:36must have been a massive advantage in our ancestors' struggle for survival.
07:43Those animals with eyes tuned in to finding the richest foods were more likely to survive and pass on their
07:51genes.
07:52And so colour vision spread until their descendants, including us, were seeing in glorious technicolour.
08:08With our three types of colour receptors, our eyes can see up to a million different colours.
08:21Our colour vision is a sensory gift.
08:24There are relatively few other mammals that see all the rich and varied colours that we do.
08:30And that goes all the way back to our monkey ancestors searching out the most tender leaves,
08:37the ripest fruits, in those forests 30 million years ago.
08:48Our ancestors flourished in those forests for millions of years,
08:53with first monkeys, then apes, exploiting the abundant food there.
09:04And maybe they would have stayed in the trees if it hadn't been for a series of major climate changes
09:12that brought the search for food out of the trees and down onto the ground.
09:27From around three million years ago, the global climate was fluctuating and becoming cooler and drier.
09:33And we know from studies of ancient climate, but also by looking at the animals that were around at the
09:38time,
09:38that the woodlands were shrinking, whilst grasslands were expanding.
09:44So this was a really important potential habitat, if apes could manage to adapt and find food here.
10:04Apes came down from the trees to walk, on two legs, out across the savannah.
10:14Fossil finds have revealed at least six different species of upright walking apes living in Africa around this time.
10:23Exactly how they relate to each other, or to us, no one can be certain.
10:28All we know comes from a few fragmented fossils of species like Australopithecus africanus and Paranthropus boise.
10:41But it's clear that their bodies were shaped by the search for food.
10:49This peculiar-looking creature is, believe it or not, part of our ancestral family tree.
10:55He was an upright walking ape, but only about a metre tall.
11:00And he's got a tiny brain case here of less than a litre in capacity.
11:05He's got an extremely wide face with flaring cheekbones,
11:10and a big muscle would have passed up here, going right up on the side of the head, to this
11:15crest on the top.
11:17And that is temporalis muscle, which operates the jaw.
11:20You can feel it on the side of your own head, when you chew.
11:25He's got absolutely massive jaws and teeth,
11:30and although his proper name is Paranthropus boise,
11:33these earned him the nickname of Nutcracker Man.
11:40From the shape of his face, it's long been thought that Nutcracker Man survived on the dry savannah
11:45by eating hard, dry foods like nuts and seeds.
11:53But whatever they were eating, they eventually died out.
12:01Whereas it seems our ancestors were eating something very different.
12:10And I'm on the hunt to find it.
12:18The only trouble is the evidence is being guarded by a formidable predator.
12:30Well, we're driving out to try to find some lions.
12:40The clue I'm looking for is hidden deep within their food.
13:09Look, there's a buffalo skull, and in fact there's a whole skeleton,
13:14Allyson's scattered around here, so do you think we're getting close to them?
13:17Yeah, we are getting closer.
13:30There's one! Look, there's a big male.
13:36There's a magnificent male just lying there under the trees.
13:41He's fantastic.
13:45They're mating!
13:49They have no shame, these lions.
13:54They're just such huge animals.
14:00And these were the predators that our ancestors were sharing their environment with.
14:14And the lions have found food.
14:20It seems like he's worked up a bit of an appetite, which isn't surprising, because when the females are in
14:24season, they'll be mating six, seven times an hour.
14:29Anyway, he's having a break now.
14:30It's extraordinary to watch him tucking into this animal.
14:34He's gone for the soft belly, first of all, pulling out the guts, and he's gradually working his way deeper
14:38and deeper into the flesh.
14:39And the clue I'm looking for is actually hidden within that meat, and that's because most of the animals that
14:48lions kill and eat are carrying parasites.
14:52And as strange as it sounds, those parasites can tell us something about our ancestors.
15:09The meat lions eat is riddled with tapeworm larvae, which grow into huge tapeworms inside the lion's gut, up to
15:18five metres long, attaching themselves to their host with barbed hooks and leeching off their food.
15:26Through that middle one.
15:29Oh, these really disgusting animals are the stuff of nightmares.
15:37Yet they're incredibly revealing.
15:40Genetic studies have discovered that the lion tapeworm is almost identical to a tapeworm found in humans.
15:50In fact, it's so similar, it seems likely that humans got this tapeworm from lions, but you can't catch these
15:58parasites directly from another meat eater.
16:02You can catch it by eating the same meat.
16:06So this suggests that humans at some point were eating exactly the same animals that lions were eating, big herbivores
16:15like antelopes in Africa.
16:17Not only that, but it seems that we can pin a date on this.
16:20Genetic studies suggest that that transfer of the tapeworm to a new host, to humans, happened sometime before 800,000
16:30to 1.7 million years ago.
16:37For decades, the idea of our ancestors as meat eaters and hunters has only been a theory guessed at from
16:45fossil remains and stone tools.
16:48But this is proof, not only for eating meat, but eating big game.
16:54Proof that is living inside our guts today.
17:01And by dating it, we're able to guess who this meat eater was.
17:15Homo erectus.
17:28This is a replica of a fossil skull that was found here in Kenya in 1975.
17:33It belongs to a species which is called Homo erectus or sometimes Homo agaster.
17:39And he looks very different from species that had gone before.
17:44He has a smaller face.
17:46He would have been much taller and would have had long legs as well.
17:50A lot more like you and I.
17:57Homo erectus had a body shape almost identical to modern humans, with long legs and a narrow waist.
18:05He was amongst the earliest apes to deserve the name Homo, meaning human.
18:10And he used tools to butcher meat and perhaps even to kill it as a hunter.
18:19And this idea of man the hunter has been used to explain all sorts of changes in intelligence, in bodies
18:28and behaviour.
18:30One of the most obvious ways in which meat eating is thought to have changed us is in the shape
18:36of our faces.
18:48Oh, this is a great collection.
18:51Dr. Peter Ungar is a world authority on our ancestors' faces and teeth.
18:57He's been looking at how a changing diet might have affected the shape of our ancestors' jaws.
19:03If you look at this earlier human ancestor, they are large, flat teeth and kind of bulbous in shape.
19:12But when we move on to Homo erectus, what you see here is you see smaller teeth.
19:18Yeah.
19:19Thinner tooth enamel.
19:20And in fact the face has responded as well.
19:22It's much more slender, what we call gracile, without the big heavy chewing muscles.
19:28Yeah, the cheek bones are very neat, aren't they?
19:30Yes, they are.
19:31This is much more human-like in its general configuration.
19:36Homo erectus' smaller teeth meant a smaller jaw.
19:44And he lost that ape-like snout of earlier ancestors like Australopithecus.
19:54With a flatter face shape, Homo erectus looks much more like a modern human.
20:05To see how well our teeth and jaws are adapted to eating meat, we're going to put them to the
20:11test.
20:12With a machine designed by Jean-Francois Mullinet, one of Peter's colleagues.
20:19Known as the Bite Master, this machine uses a sophisticated array of motors to precisely mimic a natural chewing action.
20:29First, we try the large, flat teeth of Australopithecus.
20:34I'm slightly nervous about this because it did look quite vicious.
20:38Okay.
20:38That should do it.
20:39Would they have been able to chew through meat?
20:51Well, it hasn't actually bitten through.
20:54It's just kind of squashed it.
20:55Compressed it.
20:56Well, those teeth aren't very well suited for shearing or slicing through tough foods like meat.
21:01It's kind of like a pound of steak with a hammer.
21:09So, if our early ancestors' teeth can't cut it with meat, let's see what three million years of evolution have
21:16done for meat eating.
21:17With a cast of my teeth.
21:21It feels quite old to see my own teeth getting into this machine.
21:25You want to see what it does with a piece of meat?
21:28Yeah, I'm vegetarian though.
21:31What if I've got meat eating teeth?
21:33Let's give it a shot.
21:34Shall we have a try?
21:40Good job.
21:41Yeah, you can see it's slicing through. That's amazing.
21:50Take this piece of meat out now.
21:52And that is amazing.
21:54You can actually, it hasn't quite pierced through, but you can see the light through that piece of meat now.
22:02Absolutely.
22:03Wow.
22:05The smaller, sharper teeth that evolved in all our mouths seem well adapted to shearing through the tough muscle fibres
22:13of meat.
22:15And these are the teeth of a vegetarian, by choice.
22:18By choice.
22:20Not by evolution.
22:25But Peter's research doesn't stop there.
22:30He's been using the latest technology to analyse the surface of our ancestors' teeth at a microscopic level.
22:41Tooth enamel is the hardest substance in the entire body.
22:45But incredibly, every time you eat, your food leaves its mark.
22:51The evidence of your diet is etched onto the surface of your teeth in the forms of scratches and pits.
23:00Look at that. That's gorgeous.
23:02You're looking at an event that happened in a moment in time, something like 3.3 or 3.4 million
23:08years ago.
23:09You can't get, I mean, the connection between yourself and your ancestors is right there.
23:14I mean, it's like footprints almost.
23:16From these scratches, Peter can tell what our ancestors were eating.
23:20And he's made a surprising discovery.
23:24This is cool. Get ready for this.
23:27Boom.
23:28Look at those big, heavy pits.
23:30Yeah, they're like craters in the surface of the teeth.
23:33That's right.
23:33So who's this?
23:34This is Homo erectus.
23:36Here it is in three dimensions, and we can rotate it.
23:39Look at that.
23:41Big, heavy gouges taken out of that Homo erectus.
23:45Okay, so what's caused that?
23:47Well, this particular individual unquestionably ate something hard and brittle.
23:51A nut, a seed, a root, a hard tuber, something like that.
23:55But this is Homo erectus with its smaller teeth that we wouldn't expect to be eating these really, really hard
24:00foods.
24:01That's right. But here's a different one. Check this out. Here's another Homo erectus.
24:05This individual ate tough foods.
24:08So what do you think these Homo erectus individuals could have been eating them to get scratches like that?
24:14Well, it could be grasses, or in this case it could be meat.
24:17Right.
24:18But I think what's most important here is that if we take the whole range of Homo erectus specimens, it
24:25looks very much like a species with a very variable diet.
24:29So this is really interesting because previous theories of human evolution have put forward meat eating as being this real
24:37fundamental change that happened.
24:39And what we seem to be saying here is that, okay, meat was perhaps part of the diet, but the
24:46real key to it was that the diet is getting much broader.
24:49Absolutely. I think meat is part of it, but there's more to the story.
24:55Meat might have shaped our teeth, but our ancestors were eating much more.
25:01And we don't have to go far from teeth to find out what else was in that varied diet.
25:18I'm a vegetarian, so I know that it's possible for a human being to survive for a number of years
25:23without eating any meat at all.
25:25So I'm not surprised that meat eating wasn't the only change in our ancestors' diets.
25:31There's some very interesting new evidence which suggests we adapted to a new source of food which was crucial to
25:39our survival.
25:40And the evidence is found in our mouth, in our own saliva, our spit.
25:49Scientists have been comparing our saliva with that of chimpanzees, with whom we share a common ancestor going back about
25:56six million years.
25:58Whilst our early ancestors were probably eating a diet similar to that of chimpanzees today,
26:04we have since evolved to live on different foods, and our saliva has changed.
26:11Zoo manager Chris Hearn has trained the chimps at Twycor Zoo to open their mouths for dental checks,
26:18so we can try to get a sample of their saliva.
26:21I'm going to ask him to open his mouth on a cue, which is like that, and he should open
26:26his mouth.
26:27And then I'm going to take a swab. Hopefully he's got some saliva in there for us.
26:31Yeah. And we'll take it from there.
26:33Got some gloves on, ready to take the swab.
26:40Oh, Kip, you're being ever so good.
26:44Chimp's saliva, like ours, is packed with enzymes which start to digest our feed even before we've swallowed it.
26:50Thank you, Kip. Thank you, Kip. Here you are.
26:53Wonderful. Right. Okay. Let's go and test this saliva. Okay.
27:00Any differences in the enzymes between their saliva and mine can tell us about the specific foods we've evolved to
27:07eat.
27:09Right. Now I'm going to try and wring out the chimp spit.
27:14And this is looking great.
27:20Now I've just got to produce some of my own.
27:24Excuse me.
27:31I've got to produce some of my own.
27:32Then I add flour.
27:34And iodine.
27:36This test should show how much of an enzyme called amylase is in each sample of saliva.
27:42The lighter the colour, the more salivary amylase is present.
27:48After just a few minutes, the chimp sample has turned black.
27:54Whereas my human sample is still yellow, clearly showing that my saliva has much more amylase.
28:03Now this is really interesting and I'm thrilled that this little experiment has worked because it reflects the results of
28:11the much larger study,
28:12which actually looked at the levels of the enzyme amylase in human saliva and chimpanzee saliva and found that we
28:21humans have six to eight times as much of this enzyme in our saliva as chimpanzees do.
28:27Amylase breaks starch down into sugars.
28:30It suggests that we are specifically adapted to eating starchy foods.
28:44It means that at some point in our evolutionary journey, starch must have become really important to us.
28:52To find out why, we need to go back to where we came from.
29:00This remote part of East Africa has been home to humans for millennia.
29:11I'm on my way to meet an extraordinary group of people who live here in eastern Tanzania.
29:16They're called the Hadza, and they're a modern people, but they're living in a similar environment and eating similar things
29:24to our ancestors.
29:32The Hadza are some of the last nomadic hunter-gatherers on Earth.
29:36And in the 21st century, their diet still harks back to that of our ancient ancestors.
29:46Ah, there's some little children.
29:49Oh, this is amazing.
30:00Alamena'.
30:01I'm on your own, untie.
30:03Gah, I'm on your own.
30:04I'm on your own.
30:04I'm tahnè, I'm tahnè, I'm tahnè.
30:09Ah, I'm tahnè.
30:12Ah!
30:16The Hadza live in mobile camps moving on every few months.
30:20and they live on what they can find in this arid environment.
30:26Meat is prized above all and the men go out hunting most days.
30:35I'm really excited this morning because one of the hunters has agreed to take me out with him hunting,
30:42which is just so unusual.
30:44Normally it's forbidden for women to go along and hunt,
30:47so I'm in a really privileged position.
30:50I'm tired. How are you?
30:56I'm tired.
30:57I'm tired.
30:58I'm tired.
30:58I'm tired.
31:00I'm tired.
31:01I'm tired.
31:02I'm tired.
31:04I'm tired.
31:05I'm tired.
31:06I'm tired.
31:09I'm tired.
31:09I'm tired.
31:09Click languages like Hadzanay may be close to the earliest human languages.
31:14We can set off now. Are you ready?
31:16I'm tired.
31:17Fantastic.
31:27Nyanza, what are you looking for? Are you looking mainly for birds or are you looking for other animals?
31:33At the house to me?
31:34I'm tired.
31:35I'm tired.
31:37We're going to hear birds, we're going to hear birds, we're going to look for birds, we're going to watch
31:43a Squidward and throw them.
31:50Nyamza is one of the camp's best hunters, and like most Hadza men, usually hunts on
31:57his own.
31:59A Hadza hunter will focus on big game if he can, but finding anything in this parched
32:06bushland is hard.
32:12It tends to be the older men, in their 40s and 50s, who bring back most meat.
32:20Experience counts for a lot here.
32:40Temperatures are already soaring, and it's only mid-morning.
32:46A Hadza hunter may cover about six miles in his search for food.
32:56This is certainly hot and tiring, and I'm not even keeping as alert as Nyamza is. He's constantly
33:02on the lookout for any movement that might tell him that there's an animal about.
33:26a tiny bird.
33:29We're two hours in, and still no luck.
33:37The Hadza love meat when they can have it, but it's not a reliable source of food.
33:43only one in 29 Hadza hunts is successful in terms of the men coming home with big game.
34:08It's clear I'm slowing Nyamza down, so I let him continue while I head back to camp.
34:15So Nyamza, thank you so much for letting me come with you, and I'll let you go off on
34:19your own there.
34:22See you later.
34:31But back at the camp, the women don't seem to be that concerned about the lack of meat
34:35for supper, because they've got plans of their own.
34:53Every day, the women head out on the search for food themselves.
35:06The third step, the women head out on the search and the women head out on the search
35:11of an island.
35:13I'm Alex.
35:15Alex.
35:16Alex.
35:17Alex.
35:17Alex!
35:18Yes.
35:19It's Nyamza, Nyamza.
35:21Nyamza.
35:22Nyamza.
35:31Unlike the men who hunt alone, the women work together and spend around four hours a day
35:38out gathering fruit and roots.
35:47The first port of call, berries.
35:58Masses of berries.
36:02So you squeeze it to get it out of the shell.
36:08It's like a tiny sweet slimy lychee.
36:12There's quite a honey sweetness to it.
36:16Karahaipi.
36:18Karahaipi.
36:19I like Karahaipi.
36:23It's lovely.
36:27But fruits like these aren't available all year round.
36:36Luckily there is something else that is always there.
36:40Something they can rely on all through the year.
36:44Tubers.
36:45Ah, okay.
36:47So these leaves belong to the plant that has the tubers underground.
36:51If you trace these back, it's these great big vine-like branches here which go down.
36:58And then hopefully somewhere under the ground there.
37:01Maybe I'll just find some tubers.
37:04Equa.
37:05Equa.
37:07Equa.
37:07Equa.
37:11Equa.
37:12Yeah.
37:14Tug it.
37:16Oh.
37:18Wow.
37:19That's the end of it.
37:21Look at that.
37:24It looks like a cross between a, I don't know, a root and a bit of a spindly sweet potato
37:30potato maybe.
37:33And just like a potato, this tuba is a staple food packed full of energy in the form of starch.
37:42Oh, thank you.
37:49It's not unpleasant.
37:51It's quite nice.
37:54It's quite juicy actually.
37:58When you first bite into it, it's a bit like celery.
38:01But it would be the most fibrous, tough celery you'd ever eaten.
38:07It's got a lovely nutty flavour to it.
38:10It's nice.
38:12And of course, I've got that very powerful saliva with plenty of amylase in it so I can immediately
38:17start breaking down the starch and benefiting from the sugars it contains.
38:28So, in an uncertain world where men often come home empty handed, the humble tuba is sometimes
38:35all there is to eat.
38:39We don't know exactly how our ancestors lived millions of years ago, but we can assume they
38:46were living on similar foods.
38:48And it's likely the enzymes we all have in our saliva evolved because tubas were so often on the menu.
38:58I'd like to ask everyone if they think the women bring more food in than the men.
39:07Yes.
39:08Yes.
39:08Yes, I did.
39:10Yes.
39:10And they had to eat it.
39:12Yes, they were very short.
39:18Yes.
39:18They will eat it.
39:24Yes.
39:27Yes.
39:27I know that women already have a drink.
39:29Yes, they are like no, I don't…
39:38Without them and the tuber, survival here would be impossible.
39:48When food is scarce, being able to eat a broad and flexible diet is an obvious advantage.
39:55And it meant that early humans, like Homo erectus, became experts at survival.
40:01But it didn't stop there.
40:04The ability to survive by eating a great variety of different foods, from fruit and tubers
40:10to meat, meant that our ancestors weren't restricted to one particular type of environment.
40:17And this meant in turn that they could spread out into new habitats and eventually colonise
40:24the globe.
40:29From around two million years ago, Homo erectus left Africa.
40:35And they were just the first of several human species who would go on to populate the globe.
40:42Their ability to eat a varied diet meant they could survive virtually anywhere.
40:49From arid savannah.
40:52To the freezing Arctic.
40:56To temperate woodland.
41:16This is our old friend, Homo erectus.
41:19And as far as we know, these were the first people to expand out of Africa and to spread
41:26right across Asia.
41:28Then 600,000 years ago, another species appears in Africa and in Europe.
41:34Homo heidelbergensis.
41:37Thought to be descended from Homo erectus, he was similar in build, but with a bigger brain.
41:43And it's thought that he, in turn, evolved into another species.
41:48200,000 years ago, someone else appears on the scene.
41:51And this time, it's us, Homo sapiens.
41:59We originated in Africa and then spread out right across the globe.
42:05But as well as population expansion, there's something else very obvious going on here,
42:10and that's an increase in brain size over time.
42:14Large brains need a lot of energy, and it's always been thought that what fuelled brain
42:19growth was meat, but a new idea suggests it might be linked to something even more powerful.
42:28Fire.
42:29A flame.
42:32Fantastic.
42:33I've started a fire.
42:35Fire.
42:48There's something really magical about starting a fire from nothing.
43:01Fire.
43:02I really don't think that we can underestimate the value of fire to our ancestors.
43:06It would have offered them protection, warmth during cold nights and in cold climates.
43:12Light after the sun has gone down.
43:16But it's incredibly hard to know when exactly our ancestors first learnt to control fire.
43:24Fires are just so spectacular when they're burning, but of course when they've burnt out,
43:28there's so little left, just a thin layer of ash on the ground.
43:32And so it's not surprising that it's really difficult to pick up the traces of the first fires that our
43:38ancestors would have controlled.
43:41There's some evidence going back one and a half million years ago that our ancestors may have controlled fire,
43:49but by the time our own species Homo sapiens is around, we're using fire all the time.
43:56And we get an idea of what they were doing with fire from charred remains.
44:01Things like pieces of burnt bone, charred hazelnut shells.
44:06They were cooking.
44:11I've got these burdock roots, they'll probably charred to nothing.
44:22Well, I can truthfully say that roasted burdock root is quite tasty.
44:28But cooking doesn't only make food more palatable.
44:35Recent research suggests it was cooking, not meat, that fuelled the evolution of our big brains.
44:46It was cooking that made us human.
44:57This theory has given rise to a new wave of scientific research,
45:01investigating the advantages that cooked food has over raw.
45:07And I'm going to demonstrate this in a very basic way.
45:11First, by eating a quarter of a day's calories in raw carrots.
45:25Right, it's just taken me about five, six minutes to eat a single carrot.
45:31So if I was trying to survive on raw carrots alone, I'd be munching my way through them for eight
45:37hours a day.
45:40Not only does eating raw food take a long time.
45:44Do you want a swap?
45:47But actually digesting it uses up energy.
45:53For every hundred calories of raw food I eat, I use up to 25 calories chewing and digesting it.
46:04Right, that is the end of my last raw carrot.
46:08And I'm really glad because it's taken me hours to eat them.
46:13And now to see the difference cooking makes.
46:16There's so many of them, they barely fit in the calendar.
46:20When you cook something like carrots, you're not actually altering the calorie content.
46:25But there is something crucially different about them.
46:41Well, I've nearly finished.
46:42And this half of the experiment was much easier.
46:46I can get through a cooked carrot in probably half the time it would take me to chomp my way
46:52through a raw carrot.
46:54Cooked food is much easier to digest than raw.
46:58And this simple fact holds the key to why cooking has been so important in our evolution.
47:05Not only is cooked food easier to chew, it takes less energy to digest it once it reaches our guts.
47:11Which means that we effectively get more energy from cooked food because we put less into digesting it.
47:18And although cooked food contains the same amount of calories as raw food.
47:22We can get at more of those calories by cooking it.
47:25With some foods up to 35% more.
47:29And some scientists believe that it was this extra energy from cooking that was crucial to supporting the growth of
47:37our big brains.
47:44Over millions of years our search for food has taken us from fruit eating monkeys in the forest to hunters
47:52and gatherers striding out onto the open plains.
47:57It's driven the development of tools and the control of fire that have taken us across the globe.
48:04But it hasn't just changed us physically.
48:08It's done something else.
48:09It has shaped our behaviour.
48:20We evolved as hunter-gatherers living on similar foods to the Hadza.
48:46Finding food shapes their society but it has affected all of us.
48:55It seems that the Hadza and presumably our ancestors too found a very efficient and effective way of surviving here.
49:05Men and women each have different and distinctive roles.
49:09So the women go digging for tubers and collecting berries.
49:14Whilst the men go out hunting for meat and honey.
49:18They'll eat some of it while they're out in the bush but they bring a lot of it back home
49:22to share.
49:23So it makes sense to pair up.
49:28Having a partner to share food with is a massive advantage in this harsh environment.
49:34And many Hadza men and women marry for life.
49:48Sharing food like this is thought to be the origin of pairing up and staying together.
49:53wrap up.
50:00Beakulu, how did you get married?
50:03Was there a ceremony?
50:05We bought a pretty underground for instance to live for example.
50:10We were shown to be queer.
50:23Do Hadzabe men always just have one wife at one time?
50:37Madhulu, how long have you and Pendo been married?
50:41I'm done with.
50:43And people outside your family, how might they know that you're married?
51:00Pendo, what do you think the benefits of being a married woman will be?
51:20And are you looking forward to having children together?
51:23Yes.
51:38Hadzabe women typically have around five children, which is hard work.
51:45It takes a Hadzabe woman around 13 million calories to raise a child from conception until it's weaned.
52:08And she can't physically do it without support.
52:15So choosing the right partner is one of the most important decisions a woman here has to make.
52:24So what do you think makes a good Hadzabe man?
52:28What would make you love him?
52:41Anything else?
52:42A nice face? Maybe a tall man?
52:45A nice face, the good one will be able to pay.
53:00Hadzabe women work hard to bring in food for the family, and they want a partner who will do the
53:06same.
53:06I think it makes perfect sense in this environment for the women to be so
53:10choosy about the men whom they marry because if those men aren't good hunters
53:16good providers the women have a lot to lose and women's preference for good
53:22hunters is thought to have shaped the way men behave wherever they live
53:32even when there's nothing to hunt men can still find ways to show off their prowess to women
53:46the latest research shows that men are in some way hardwired to show potential partners they've got
53:52what it takes and they do it by taking risks and we're going to show you how with some of
54:01Britain's best skateboarders rather strangely we've asked them to try to perform a trick that
54:09they're not very good at that they're still struggling to learn and then in fact they're
54:13likely to fail at the important thing is that they're taking a risk whilst practicing their
54:25difficult tricks there's a moment when the skateboarder makes an unconscious decision
54:29either to play it safe and give up on the trick by kicking the board away so they can land
54:35safely or
54:36to live dangerously to stick with the trick and try to land the board which is risky to start with
54:46a
54:46male researcher monitors how often they take a risk and how often they play it safe
54:56what happens when we introduce some attractive young women into the equation
55:20in the presence of female observers the men seem to be gambling more in fact the original research
55:27showed that risk-taking almost doubled when an attractive woman was present
55:36and that it seems comes down to testosterone
55:41scientists have found that having women around increases the skateboarders levels of testosterone
55:47by up to 40 percent forcing the men to display their potential as a modern-day version of a good
55:55hunter
56:00men showing off to women by taking risks could be a throwback to the food gathering strategies of our ancestors
56:07by taking risks men are signaling that they're likely to be good providers
56:12and therefore better mates
56:14so it seems that men have an excuse for behaving the way they do
56:19they're designed to be show-offs
56:26it turns out that food has driven the evolutionary journey of both the men and women of our species homo
56:34sapiens
56:37so much about us today from the way we feel about each other to the ways in which we think
56:44and behave
56:44and even the way we look we can trace back to our hunter-gatherer ancestors in africa and their search
56:51for food
56:52but since then we have spread out to every corner of the globe and our population has exploded
56:59and what enabled that was farming
57:08in the last 10 000 years we've gone from being nomadic hunter-gatherers to large-scale industrial farmers
57:22that has enabled a population explosion
57:30and changed the face of our planet
57:33with over a third of the land on earth
57:37taken over by farming
57:48our relationship with food has had a powerful effect on us
57:52shaping the structure of our bodies and our societies
57:55and having a massive impact on the environment around us
57:59we've gone from being forest-dwelling fruit-eating apes
58:04to becoming a species that can survive
58:06finding food just about anywhere
58:09because we put it there
58:12we're naturally able to eat a diverse variety of foods
58:16and through the use of culture through cooking and farming
58:21we've widened that range even further
58:23and that underpins our success as a global species
58:31and alice is back on bbc hd tomorrow night at nine
58:34with the final part of the origins of us
58:36next this evening we have a crack at uncovering the secret life of ice
58:41and we'll talk to you next time
58:42bye
58:53bye
58:54bye
58:55bye
58:57bye