NOVA

(snorting)

NARRATOR

Horses. Powerful, graceful, and thunderously fast. No animal has made a greater impact on society or given humans more freedom and mobility than horses.

DAVID ANTHONY

The thrill that people still get today from riding a horse at top speed, there's nothing like it. Whereas if you get on the back of a cow... (mooing) it's not that great an experience.

NARRATOR

Centuries before Egyptians built the pyramids, Eurasian nomads unlocked the power of horses and used them to reign supreme over vast territories of the ancient world. But how did they do it? (speaking

NARRATOR

Follow anthropologist Niobe Thompson as he visits the last of today's horse-riding cultures and explores archaeological sites and genetics labs seeking to unlock the mysteries of the world's first riders.

ESKE WILLERSLEV

The horse transformed what it means being human. It gave the possibility to explore the world in a way that had never been possible before.

NARRATOR

But horses could also bring terror at the hands of brutal raiders, and even pandemic disease. Time-travel back to when prehistoric people began capturing wild horses and rode them like a tide that would forever change the course of human history. "First Horse Warriors," right now, on "NOVA." (snorting) (whinnying faintly) Horses are magnets for our attention. They draw us in, almost demanding we look at them. (whinnying) For most people today, just seeing a horse is a rare sight. Perhaps only a couple of times a year, watching races like the Kentucky Derby. But not so very long ago, horses were everywhere-- woven into the fabric of our daily existence, in the countryside and even in cities.

ANTHONY

The city of New York had tens of thousands of horses that were doing all the work that trucks do. And they were also doing all of the work that taxis do today.

NARRATOR

We don't depend on horses anymore, but few animals have been as important to the rise of civilization. For thousands of years, they were our long-distance vehicles-- the muscle and speed we needed to master the world. But how did this unique partnership form? Who were the first people to unlock the power of horses, and what happened once they did? Recent discoveries in archaeology and paleontology, genetics, and even linguistics are revealing the identity of the world's first riders, as well as the extraordinary relationship humans forged with horses and how that bond would change the very course of history. (whinnying) Horses appeared on the scene long before we did, but surprisingly, looked nothing like the majestic creatures we see today. 55 million years ago, they are small, and move like agile dogs. This Dawn Horse is well suited to the tropical forests covering much of the Earth back then, living and foraging among the dense foliage.

THOMPSON

It stayed hot for millions of years. And in all that time, Dawn Horse hardly changed at all. And then, about 15 million years ago, the Earth began to cool.

NARRATOR

And when it does, forested regions distant from the Equator transform into open plains covered with grasses. And here, the small, dog-like horse evolves to avoid predators, growing sleek, tall, muscled, and fast. Although horses first appear in North America, as their numbers grow, they migrate across Beringia, the land bridge that once connected the continents. More than 100,000 years ago, herds of horses in Europe and Asia prove a rich source of meat for Stone Age hunters.

ANTHONY

People hunted horses. They are meat on the hoof. They don't have sharp teeth. It's not like hunting cave lions, you know?

NARRATOR

And early hunters know how to find migrating horses.

ANTHONY

Horses are relatively predictable animals. And they tend to follow a regular system of water holes and grazing places.

NARRATOR

At Solutr in Central France, there's evidence ancient hunters regularly ambushed horses.

SANDRA OLSEN

At Solutr, for about 20,000 years, people were driving wild horses into a kind of cul-de-sac and then killing them with spears for food.

NARRATOR

This chunk of earth excavated at Solutr is dense with horse bones, revealing just a tiny fraction of the tens of thousands of horses slaughtered here over the centuries. At Chauvet Cave in Southern France, the importance of the horse to our Stone Age ancestors is on clear display. When you look at this marvelous wall, you see all the major animals the Stone Age world depicted. You've got reindeer and mammoths, big cats. But the horse seems to play the most prominent role. From their art, many experts believe ancient humans were making a spiritual connection to these animals. Despite such reverence, prehistoric humans may have over-hunted horses, and by about 10,000 BC, when a changing climate may have also depleted their numbers, horse herds became scarce in Europe and disappeared entirely in the Americas... where they would not return until European explorers sailed them back in ships. But on the grassy steppe lands of Central Eurasia, the descendants of horses that migrated from America flourish. And it's here that many experts believe prehistoric humans eventually discover how to ride them. The steppe refers to this long grasslands plain stretching over 5,000 miles from the edge of today's Europe all the way to Mongolia in Asia. It's a harsh environment-- cold in the winter, hot in the summer, and in many places, too dry for agriculture. But you can pasture animals, and these Kazakh herders are following in the footsteps of their nomadic ancestors, who may have been among the first people to capture and ride horses. (speaking local language) And Niobe has come here to see what he can learn from them. (speaking

local language)

(speaking

NARRATOR

Raising sheep, goats, and cattle is a rugged, outdoor existence. But horses make herding easier-- especially when moving grazing animals to new pasture. And Niobe pitches in. It was surely a big change to turn wild and wary steppe animals into the working horses we see today. So who were the first people to tame wild horses, and how did they actually do it? 5,500 years ago, the people who lived at this site in Kazakhstan may have been the first culture to master the horse. The site was discovered 40 years ago when Russian archaeologist Victor Zaibert noticed circles in the earth that turned out to be large houses belonging to a steppe people anthropologists call the Botai. Prior to creating this village, the Botai are strictly nomadic, living off the land, foraging and hunting, and eating what they could find. But then they settle down and change their lifestyle. By the vast number of horse bones uncovered at the site, they began eating horsemeat almost exclusively. But is eating horses the only use the Botai had for these animals? Or could they be riding them, as well? That question has roiled the academic community for decades. Almost got a bevel on this side, too. This is the same guy? Anthropologists David Anthony and his wife, Dorcas Brown...

ANTHONY

There's the skull...

NARRATOR

...have long maintained the Botai were among the first people to capture and ride horses. And they've pieced together what they believe is convincing evidence by looking for wear marks a riding bit might make on their teeth.

THOMPSON

A bit is part of the bridle or reins. They can be made of leather or metal, and they go in the horse's mouth just here. So when I apply pressure through the reins, the bit tells the horse what I want it to do.

NARRATOR

And David Anthony believes he's found evidence of bit wear in the jaws of Botai horses.

ANTHONY

There is a gap between the molar row and the incisors. And if you put a bit in the horse's mouth, it sits on top of very sensitive tissue. And so by pulling on the bit on one side, you pull the bit down against the gum, and the horse will turn its head in order to avoid that pressure. You pull the rein on the other side, and the horse will turn its head to avoid that pressure. And that's how a creature as puny as a human can control an animal the size of a horse.

NARRATOR

But a horse doesn't want a bit constantly bearing down on its gums.

ANTHONY

The horse can use its tongue to push the bit up and put it onto these teeth to get it off of the soft tissue, where it can't hurt them anymore. And then in this position, if the horse grasps the bit very firmly between the lower teeth and the upper teeth, it can keep the bit off of its tongue and gums. So we were looking for wear on the front part of the tooth here.

NARRATOR

They examined hundreds of samples, looking for evidence of bit wear...

BROWN

You can see that it's broken. He really, he chewed all the way through this bit.

NARRATOR

...and feel confident they found it.

ANTHONY

This is a cast of a tooth from the site of Botai that's 5,000 years old. This is the tooth of a modern horse that's been bitted. And both of them have wear on this front cusp right here.

NARRATOR

Despite this apparent evidence, not every expert believed Anthony was correct.

ANTHONY

There are people who did not believe that the marks that we saw on the teeth were caused by a bit, because those kinds of features can be caused by natural malocclusion in horses.

NARRATOR

Beside refuting the bit evidence, other experts argue that images of humans riding horses or chariots do not appear until about 2000 BC, or 1,500 years after the Botai. If the Botai had become riders, surely this would have been depicted in art. This is the same guy? So are Anthony and Brown correct about teeth wear as evidence for riding? Archaeologists digging at Botai village have been hoping to find other evidence that the Botai had become riders. They know the people are smoking, cooking, and eating vast quantities of horsemeat. And they found large concentrations of horse dung and holes from fence posts, indicating the Botai are keeping horses in corrals-- something David Anthony believes makes sense for a culture that had become dependent on horses. It's easier to kill a horse in a corral than it is to find the horses, go out to the place where you have to ambush them, kill them there, and lug it back to your settlement site. It would be a lot more convenient if you just had horses in a corral, and you could go out and get one whenever you wanted a meal. Beside serving as a food larder, the corrals could also mean the Botai are breeding and domesticating horses, like other cultures are doing with cattle, sheep, and goats-- living off these animals for milk, meat, wool, and other products. If the Botai are domesticating horses for the same reasons, this would naturally bring greater interaction and familiarity, making attempts to ride them much easier. And archaeologist Alan Outram set out to prove the Botai had domesticated horses by focusing on milk.

OUTRAM

If people could milk cattle very early on, then people that were living off horse products, why would they not also milk horses? And if you've got horse milking, you've got a smoking gun for domestication, because no one's going to argue with you that people are running after wild horses to milk them.

NARRATOR

If the Botai had been milking tame horses, these broken pottery vessels may have once contained their milk. So Outram brings them to this lab at the University of Bristol....be a drop in horse populations... He wants chemist Richard Evershed to use a process called an isotopic analysis... Be interesting to know what this little blip is down here....to see if he can find residues of milk fat still clinging to the pottery, even after 5,000 years buried in the ground.

EVERSHED

The basis of what we do is to look at the organic compounds, the fats, that have absorbed into the wall of the pot. And actually, they are pretty tough to extract. And we've had to develop some methods to actually open up the structure.

NARRATOR

At first, it's all handwork.

EVERSHED

We drill off the surface of the pot to reveal a, sort of a fresh ceramic surface. And then we literally break off a small piece, about two grams, and we put it into a pestle and mortar, and we literally grind it to a powder. We pound it to a fine powder. And what that is doing is opening up the pores in the pot.

NARRATOR

This will hopefully free traces of specific chemical fingerprints, called isotopes, of any organic substance the pottery once contained, including milk fat. (machine whirring) The powder is then liquefied and placed into this machine that heats it and analyzes the chemical signature of the gas vapors being released to see if those signatures match the ones known to come from horse fat. So these are the results of the isotope analysis. And you can see these two major peaks. And these are the fatty acids that tell us we've got an animal fat. A good start. But evidence of fat doesn't necessarily mean milk fat-- it could be carcass fat.

EVERSHED

We can't say from just looking at these peaks exactly what type of fat we've got.

NARRATOR

And since the Botai are eating horses...

EVERSHED

And if you're cooking meat in a pot, you will obviously get the deposition of a lot of fat as the meat is cooked. So that didn't work. Yeah.

NARRATOR

They go back to the drawing board, realizing they need a way to clearly distinguish milk fat from carcass fat. And the best way to do that would be to go to the original Botai environment in Kazakhstan and gather samples of mare's milk. The grasses mares eat today should be composed of elements like hydrogen or oxygen that are similar to those their ancient ancestors ate.

EVERSHED

It's the "you are what you eat" principle. So you're inheriting the isotope signatures of different foodstuffs that you're eating.

NARRATOR

In spring, when mares are nursing, their milk absorbs elevated levels of a hydrogen isotope called deuterium that's in water and grasses. And this elevation will only be in the milk fat, not in their carcass fat. When the team analyzes the modern milk samples, they find elevated deuterium peaks that match perfectly those from the Botai pottery.

This confirms Alan Outram is right

The Botai had been milking domesticated horses.

OUTRAM

I don't think anyone can seriously argue that you haven't got decent control of animals if they're being milked.

NARRATOR

But it takes practice to milk a horse, as Niobe discovers. Milking a horse is all about tricking the horse. So what happens is, someone brings a foal in, the foal sucks the milk from the teats, the milk falls, and then they pull the foal away quickly, and someone rushes in and milks the horse. As soon as the mare knows that it's not the foal, or suspects something, something's different, the milk dries up. The mare sensed that I didn't really know what I was doing, and as soon as I got a bit of milk out, the teats dried up. They had to bring the foal back in. It's really hard. (chuckling): You know, it's just... Just a little bit. (all laughing) Only horses used to a human touch would have allowed the Botai to milk, tame, and ride them.

OLSEN

And so by the time you start to pile all of this evidence on, the people living in sedentary villages, milking the mares, eating the horsemeat, it's fairly evident that you have domesticated horses there.

NARRATOR

And gathering large herds of domesticated horses would be extremely difficult without horse riders to herd them.

ANTHONY

If you ask people who manage horses today, "How can you manage horse herds without riding horses?", they laugh at you. Of course you have to be on horseback to manage herds of horses.

NARRATOR

So despite their doubters, all the evidence points to Anthony and Brown being correct. The Botai were riding horses. But how did the Botai convince large, wild animals to let them climb on their backs?

BROWN

You choose the docile animals. So you would approach a horse, and if it ran away, you didn't get it. But if you approached a horse, and it was sort of curious and interested, then you could then begin with that horse and then go, build on from there, build a whole herd from there. (whinnying) Oh, I think the first riders were getting bucked off pretty fast. But once they figured it out, why not go long distances? Especially on the steppes, you know? You'd always wonder what's over that next horizon. I think that's what was going on. They wondered what was past that next horizon.

NARRATOR

Riding. The Botai's prey has become their companion. Riding this magical creature must have felt like breaking a law of nature. Now the Botai can herd more animals and trade with distant cultures. Their horses prime them to become the most dominant force on the steppe.

ANTHONY

You would expect the Botai people, with the advantage of horseback riding, to have really thrived. And it looks like they did great. They had these large conglomerations of people living in these big settlements. They were feeding themselves magnificently. But after 3000 BC, they pretty much disappeared.

NARRATOR

What became of the Botai and their horses? Archaeologists have found little evidence or even human remains in the village that might help them understand their fate. And that's what makes this discovery by Alan Outram's team

so important

a fairly intact Botai skeleton. I cannot stress how rare human remains are at this site.

NARRATOR

Their hope is that these bones will yield DNA that geneticists can trace to later populations that may have absorbed the Botai and become their heirs. Recovering ancient DNA is extremely difficult, but Danish geneticist Eske Willerslev has earned a global reputation for finding and sequencing the genomes of our oldest ancestors. And he's come to Botai village to see if this rare skeleton looks like it could yield DNA that has survived the ravages of time.

WILLERSLEV

Hey, guys. Hey, so you found a human whole?

OUTRAM

Yes. But you have no idea how much of the skeleton is there, huh? We don't yet. There are quite a lot of bone fragments all around. Some of them are horse bones. Yeah, yeah.

NARRATOR

Eske is impatient to get specimens back to his lab. But he'll have to wait for the meticulous process of uncovering fragile bones from the packed earth-- and then hope for the best.

WILLERSLEV

We are getting DNA out of a lot of specimens that we, six, seven years ago, didn't think you could get anything out of whatsoever, right? And now they're working. So, I mean, it's really hard to predict whether the specimen will work or not, but I'm pretty optimistic. When you have cleared the head, can we kind of remove the lower jaw to get a tooth? I think the lower jaw will come away all right. All by itself, huh? Yeah. Yeah.

NARRATOR

Eske wants a tooth, because the DNA inside is protected by an outer coating of enamel. The team gives him one. Wow, okay, this is beautiful. This is beautiful. This is beautiful. Oh, this is fantastic. (softly): Yeah!

WILLERSLEV

Amazing, yes. Thank you very much. You're very welcome. Yeah, yeah.

NARRATOR

And there's something else. Oh, hey, there's a petrous there, right? Yeah. Wow! The petrous-- a small bone that's part of the skull near the inner ear-- is a fortuitous find.

WILLERSLEV

So the petrous bone is the most dense bone in the human body. Therefore the DNA preservation is better than in other parts of, you can say, the post-skeleton material.

NARRATOR

After months of work, Eske and his team identified the genetic signature of the Botai villager. They expected to find traces of his genome in later steppe cultures. But stunningly, they couldn't find it.

WILLERSLEV

The Botai people, if you want, as far as we know, haven't left any direct descendants.

NARRATOR

Despite their resources and well-established community, the Botai somehow died out.

WILLERSLEV

It's kind of tragic irony that they do something extremely challenging-- they domesticated the horse, probably one of the most influential events in human history. But they don't take over the world with this new, major power they have. I mean, they become a dead end, right? They don't have an impact.

NARRATOR

As it turns out, we know more about the fate of Botai horses than the Botai people. French geneticist Ludovic Orlando has also come to Botai village to collect bones for DNA sampling-- in his case, horse bones, not human ones. If these are indeed the remains of the world's first domesticated horses, then Orlando believes it's very likely their genetic signature will have passed on to all domesticated horses living today. He took samples back to his lab to see if his theory was correct.

ORLANDO

I was expecting the first population of domestic horses to have been the source of all and every possible domestic horse that lives on the planet today.

NARRATOR

But when he ran the tests, the results came as a shock. I have no way to express how wrong I've been, actually. When Orlando sequenced the Botai horse genome and looked for its signature in modern horses, he couldn't find it, as if the Botai horses, like their masters, had disappeared. But then, in a surprising twist, he found them in the least likely horses imaginable. The big surprise is that it's the Przewalski horse. (whinnying) The Przewalski horse. For centuries, these unique-looking horses were thought to be the last and only wild horses on Earth, living in a remote area of Mongolia. As it turns out, they are the genetic descendants of Botai horses that returned to the wild when their masters disappeared. (whinnying) So these last of the wild horses are actually descendants of the first domesticated horses, a living legacy of their Botai masters. Although the Botai fade away, another steppe culture seizes the mantle of horse kings. They are called the Yamnaya. (grunting) Bands of nomads who roamed a territory north of the Black and Caspian seas at the start of what's called the Bronze Age. By about 3000 BC, they become the greatest horse culture of the ancient world. The most important thing about the Yamnaya culture is that they were the first culture to take advantage of both horseback riding plus wagons. Although the first wagons are heavy and crude-looking, they are a breakthrough technology. Wagons stocked with food and supplies, accompanied by horse-herded flocks, allow the Yamnaya to easily move to the best pasturelands. And in no time, the Yamnaya are out-competing other steppe cultures.

BROWN

The horses helped them increase their herds. And so they could get more sheep and more cattle and more meat. And so they became wealthier. Horse herders, could, could beat everybody out.

NARRATOR

And if anyone dares to resist the Yamnaya, here, too, the horse gives them the upper hand-- literally.

ANTHONY

It was an advantage to ride up to somebody on a horse and use the horse as a platform. The height advantage is a real advantage.

OLSEN

I think we find it hard to imagine how thoroughly they could overcome other populations who are just sitting there and unfortunately, very, very vulnerable.

NARRATOR

Over time, the Yamnaya, and other cultures they influence, develop weapons like battle-axes that are lethal on or off a horse.

FLEMMING KAHL

This battle-ax was a very important piece. The edge is not sharp. It's not very good for, for cutting wood. But used in battle for, well, breaking skulls, it's very efficient. All over Europe we find, actually, skulls which has been, well, broken by ax blows.

NARRATOR

With their horses, wagons, and weapons, the Yamnaya and other cultures they combine with begin to range ever farther from the central steppe, moving as far east as Mongolia and west into the heart of Europe. And David Anthony contends these aggressive nomads dominate almost every population they encounter, because many people begin speaking Yamnaya. (screaming) Language is connected to power or to wealth. People drop the language they're speaking and adopt a new language, because that language gives them advantages. But the Yamnaya left no written record of their language, so how could Anthony or anyone possibly know what their language looked like or sounded like?

NARRATOR

Andrew Byrd believes these words are close to those spoken by the Yamnaya. (speaking Proto-Indo-European) He's made up the story, but can trace the words back to the time they were first spoken and then reconstruct the language they came from.

NARRATOR

Linguists have long maintained that many languages in Europe and Asia, including Ancient Greek and Roman; Romance languages like French and Spanish; Germanic languages, including English and the Scandinavian languages; even Russian and Indian Sanskrit, all derive from a common language source. If you look at languages like English and Latin and Greek, Sanskrit and Russian, and you start to see these words looking very, very similar to one another. For example, if you look at the word for brother, within English, it's "brother." If you jump down to ancient Rome, it's "frater," as in our word fraternity. If you go to ancient India, it's "bratar," and if you go to ancient Greece, you have "pratar." And you could see that these words look so overwhelmingly similar. They have Rs after some sort of B- or P-like element. They have a T sort of thing in the middle of the word. They all end in R. And, and the fact that all of these things look alike can't be by chance, leading us to the... The only sensible conclusion is to say that these all were inherited from an ancient language. Linguists call this source language Proto-Indo-European. They can take a word like "is" and trace its spelling and sound pattern back through past languages to approximately when the word first appeared. They can do this with many words, like "father." And most seem to originate in the period of Yamnaya expansion. And some words, like "wheel," connect directly with the Yamnaya and only appear after the Yamnaya become dominant. You can establish that the later Indo-European languages all expanded after 3500 BC, because they have the wheel and wagon vocabulary. And wheels and wagons didn't exist. They had to be invented first. It's very much like the word "hard disk." It shows up in dictionaries in 1978. And dictionaries before 1978 didn't have the word "hard disk" in them. Because it hadn't been invented yet. And so Proto-Indo-European must have been spoken after wheels were invented. Therefore, we assume that there was some ancestral language which we can call the Yamnaya, which was the source of all of these languages. But how did these bands of nomads overwhelm other cultures so completely that people began speaking their language? Shouldn't there be some indication they had become conquerors? There is very little evidence that what happened 4,800 years ago is related to violence, that there was a massive amount of warriors coming in and just, like, stabbing and killing everybody, because we don't find evidence for that. So how did Yamnaya language and culture spread across Europe and Asia? Is there something more tangible than language to account for their dominant presence? (bicycle bell rings) Back in Copenhagen,

Eske Willerslev had long puzzled over the question

"Which ancient cultures were most responsible for the ancestry of people living today?"

WILLERSLEV

Our history far back in time is actually written still in our genes, and that means you can, you can follow human history by analyzing the genome of these ancient individuals.

NARRATOR

He was especially curious about the Yamnaya. If they had dominated large parts of Europe and Asia, then their DNA should have passed on to future generations, down to the present. His team began by sequencing ancient remains from across Eurasia, and then comparing them to a Yamnaya genome to see how widely the Yamnaya genes had spread. They then compared this data to the genomes of modern populations and put the results on what are called PCA plots. PCA is a way of understanding very simply and visually the differences in genetic ancestry between populations. For example, you put a bunch of people from Europe on a PCA, and you'll notice that the people in Northern and Southern Europe separate. The second thing you want to do on this is to overlay ancient populations on top of the modern populations and see where they lie. These two plots show modern population groups as gray dots in Europe and Central Asia. When we overlay the genomes of people who lived 10,000 and 8,000 years ago, we see almost no overlap, indicating little genetic connection to people living today. But in this plot-- representing the approximately 5,000-year-old Yamnaya expansion, the dots overlap significantly, meaning today, millions of people of European and Asian descent owe their ancestry to Yamnaya nomads of the Eurasian steppe.

NARASIMHAN

What we didn't understand from the archaeology is the extent of the movement and the impact that the Yamnaya had on genetic ancestry. But now we know that up to 50% and 30%, respectively, of the genetics of Europe and South Asia are directly descended from that of the Yamnaya. So the impact is huge, as much as any genetic ancestry that we have.

NARRATOR

And the Yamnaya could not have made such a massive and wide-ranging genetic impact without their horses and wagons.

WILLERSLEV

Anthropologists like Anthony were right that the early Bronze Age is characterized by this very significant movement of the Yamnaya peoples on horses that are very speedy, very fast into Northwestern Europe and Central Asia, and bringing with them, of course, the genes, the culture, and the language. But the majority of archaeologists, you know, didn't believe this was the case. Six-and-a-half years old...

NARRATOR

For Anthony and Brown, this was vindication. The Yamnaya had been masters of their universe.

BROWN

We were very happy. We were smiling and laughing, and going, "Oh, my God, I can't believe it's that big." But I was pretty sure these guys were roaming all over the place.

NARRATOR

But a big question remained. It appears Yamnaya numbers are small compared to the size of the populations they encountered. So despite the advantage their horses gave them, Eske wondered if there could be other factors that weakened the populations they dominated. At first we thought, "Well, maybe it's some kind of climatic changes," and we went, you know, through the climate records, and we couldn't really see anything very dramatically. And then there was, one of the archaeologists said, on the team said, "Well, what about diseases, right?" So we thought, "Well, let's look for pestis." Yersinia pestis-- the plague. During the Middle Ages, this lethal pandemic killed over half the population of Europe. If it had struck during Yamnaya times, it might have decimated local populations, clearing a path for a Yamnaya takeover. Eske decided to see if he could find traces of the plague in the bones of the Yamnaya and the people they encountered. But he would need lots of human samples to test. Remarkably, in St. Petersburg, Russia, a rather unique anthropology museum had just what he needed. Some of the museum's displays have a "Ripley's Believe It or Not" feel to them. But the real treasures are in storage, as Niobe finds out firsthand. If you're after DNA from any part of the former Soviet Union,

this is the place to come

the museum of anthropology that Peter the Great founded over 300 years ago, the Kunstkamera. So for centuries, Russian archaeologists have been coming back to these storerooms with their discoveries. And today, well, the collection of human remains is astounding.

NARRATOR

There are hundreds of skulls and skeletal remains from different time periods and throughout Asia and Europe. Oh, wow, okay. This is a large collection. And Eske has convinced the museum's archaeologist, Slava Moiseyev, to let him take back scores of teeth and petrous bones to analyze in his lab. (saw whirring) The two men work for days cutting samples...

WILLERSLEV

Nothing like the smell of fresh bone in the morning. (chuckling)

NARRATOR

...carefully documenting each specimen and literally pulling teeth. Moiseyev has one group of Yamnaya samples he knows Eske will want. This is rather strange burials, because mostly people had just single burials. And this consist of seven individuals. It's quite unusual. Oh, wow. Group graves became common for later-era plague victims. So these samples will go to the top of the stack. In the end, the museum-- like the Tooth Fairy... Okay....bequeaths Eske a goldmine of samples. And sure enough, many contained genetic evidence of the plague.

WILLERSLEV

We started screening, and, you know, bang, it just jumped out, right? I mean, so we saw fragments of it, and then we said, "Wow!" This is basically evidence of pestis and plague epidemics... (coughing)...3,000 years before any written record. So it was an amazing result. (coughing)

NARRATOR

The evidence shows the plague begins in the steppe, possibly in Yamnaya communities, and including the family of seven buried together in a single grave. So clearly at some point, the Yamnaya themselves are suffering horribly. But those that do survive probably develop immunity. And as they expand their reach, they become like the Grim Reaper on horseback, carrying plague germs with them.

KRAUSE

The plague is spreading with those people. Those people actually bring the plague into the regions that they move into.

NARRATOR

And where people have no previous exposure, only a few survive. And what happens to those survivors is an age-old story.

ANTHONY

The Yamnaya brought a really deadly disease with them that could have been responsible for a large part of the population replacement. There are other ways, though, of course, to replace a population, other than disease. You can directly kill them. And it does look like the survival of males was much less than the survival of females. You find Yamnaya tribes that regularly engaged in raiding, killing the men and taking local women. (people screaming)

NARRATOR

And using those women to produce Yamnaya offspring. The ancient world could be a very unpleasant place.

WILLERSLEV

When I started this project, I had this very romantic view of, of the whole thing, and, and kind of, you know, dreamed about, you know, living myself during the Yamnaya times, right? I have changed that conception. I'm happy to live now. (laughs)

NARRATOR

The full impact of the Yamnaya's culture, language, and genetic dominance would take centuries, passing down to other cultures they combined with.

NARASIMHAN

It's sort of a slow-rolling process. It's not like one group of people is just packing up their bags and moving off to Iberia or England or South Asia or India, wherever you want to go. But they're meeting large groups of people who are farming, and, you know, doing their thing. And then there's a hybrid culture that evolves, and a hybrid genetic ancestry that evolves. And these people then subsequently move to other parts of the world. (men calling, horses whinnying)

NARRATOR

But back on the steppe, the Yamnaya continue their nomadic ways and inspire later steppe people to take horsemanship to a whole other level.

ANTHONY

If we go back to the steppes where Yamnaya came from, horses continued to be extremely important. And in fact, a new form of military vehicle was probably invented by the people in the steppes around 2000 BC-- the chariot.

NARRATOR

Pulled by swift horses, the chariot is the first high-speed vehicle. And many ancient cultures begin using it in battle, especially on level ground like deserts. But the most significant developments come when the great horse cavalries of first the Huns and then the Mongols begin thundering across the steppe. (swords scraping scabbards) These skilled horsemen could ride and shoot at the same time and become the most lethal military force the world has ever seen... ...capable of bringing armies and whole cities across Asia, Europe, and the Mediterranean to their knees. Although these steppe warriors emerged centuries after the Botai and Yamnaya, their roots go back to those first riders and their mastery of horses.

OLSEN

If you just think of some of the great empire leaders in history, for example, Genghis Khan, or Alexander the Great, so many of them built their empire on the backs of horses. And that of course led to the spread of civilization, the spread of all kinds of technologies, the Silk Road, various trade routes. Everything hinged on having horses.

NARRATOR

The reverence ancient people had for horses, revealed first in early cave paintings, would continue for thousands of years. This bronze and gold sun chariot, discovered in Denmark, perhaps expresses this best, and is one of the most important symbols of the Bronze Age. Here, the horse is God's partner, helping pull the sun across the heavens.

KAHL

We could wonder why the horse became the most prominent helpers of the sun. But I think the reason is that the horse was, and is, even today, perhaps the most aristocratic animal that you can find, a natural choice for a divine being, the very symbol of movement. (whinnying)

WILLERSLEV

Getting the first time on a horseback here, and being able to just feel the speed, and the distance you can cover, you can see the whole possibility of exchanging knowledge, understanding the world you are in. It's a game-changer right? It's a game-changer in human history.

NARRATOR

For nearly 6,000 years, horses have been the human race's special companion, our extra muscle, our overland vehicles, and symbols of power. Horses gave us the freedom to move, and that freedom changed the very nature of human life. For all we puny humans lack, horsepower made up for it. It's hard to imagine where we'd be, what our world would look like, without horses. To order this program on DVD, visit ShopPBS or call 1-800-PLAY-PBS. Episodes of "NOVA" are available with Passport. "NOVA" is also available on Amazon Prime Video.