Genghis Khan is more legend than man. We鈥檙e not even sure when he was born: historians agree it鈥檚 somewhere in the decade that spans 1155 and 1167. That birth has itself been mythologized. Stories tell of a ray of light impregnating his mother; the baby, named Tem眉jin, was apparently born holding on to a piece of clotted blood, an omen of his later conquests. His death in 1227 is shrouded in rumours both kind and denigrating. Genghis Khan was struck by lightning. He died of an arrow wound that led to a systemic infection. He was castrated by a princess. Or maybe the bubonic plague got him in the end.
There is yet another legend about Genghis: that we are all related to him. Or that most of us are related to him. Or that a significant percentage of the planet can be traced back to him. Rumours have a way of warping in the telling.
We can trace this allegation to a scientific paper published in the early 2000s. But it all begs the question: how do we know? Do we even have DNA on a person who began life as a man but ended it as a legend?
A common Y chromosome? Whose Khan it be?
Central Asia is a land of diversity. Its geography is vast and varied, and its peoples鈥� DNA contain bits and pieces from the entire globe. An revealed that central Eurasia鈥攚hich can be as spanning the Caspian Sea all the way to Western China, including many of the former Soviet republics鈥攈as the most genetic admixture out of any population on Earth. The people who live there have in their genomes equal contributions from Europe, China, the Middle East, and India, as well as notable traces from Africa and what is referred to as the Arctic (meaning Indigenous people from the north of Europe, Asia, and North America, not polar bears).
Despite this richness, researchers in the late 1990s were deploring the fact that, genetically speaking, Central Asia was major regions of the world. Enter a paper entitled
Its corresponding author was Chris Tyler-Smith of the University of Oxford, but it鈥檚 another name, listed fourth, that caught my attention: Spencer Wells. Soon after the publication of this paper in 2003, he would lead the Genographic Project, which aimed to map human migrations from our African cradle to current day by collecting saliva samples from people all over the world. Mine was one of many, many samples they processed.
The early 2000s saw an explosion in genetic research. This specific paper鈥攚hich I will call the Zerjal paper after its first author, Tatiana Zerjal鈥攆ocuses on the Y chromosome. This chromosome, which men typically have, is tiny and has a measly 63 genes; chromosome 1, by comparison, is our longest and has nearly 2,000 genes. (If you鈥檙e wondering why I wrote 鈥渢ypically,鈥� you should read Ada McVean鈥檚 . It鈥檚 complicated.)
The Y chromosome is particularly interesting in genetics because, if you have one, you received it from your father. We can thus use the Y chromosome to explore the patrilineage: the line of men that goes from you to your father and his father and his grandfather, and on and on. That Y chromosome is not completely static, though. It will mutate, but enough of it is conserved that we can see where someone鈥檚 Y chromosome ultimately came from. That鈥檚 the information I received after I sent in my saliva sample to the Genographic Project. They extracted my DNA, amplified a number of stretches along the length of my Y chromosome, and compared it to the Y chromosome of populations all over the world. The verdict: my patrilineage traces back to Western Europe. No surprise there on my end.
Zerjal and her colleagues did exactly this using the DNA of over 2,000 Asian men, and they found something strange. Those stretches of DNA I mentioned, they鈥檙e not random. Scientists look at them because they are repeats. For example, one of them could be 鈥淐AACAACAA.鈥� I might have three of these CAAs in a row, while my neighbour could have seven. When you analyze enough of these stretches of repeats鈥擹erjal looked at 32 of them in her sample鈥攜ou end up with a sort of fingerprint. A person can have 3 repeats at the first position you looked at; 11 at the next one; 6 at the third. That fingerprint is known as a haplotype. My Y-chromosome haplotype was common in Western Europe. But there was one haplotype Zerjal and her colleagues found in their sample of Asian men that was way too common to make sense.
This haplotype, which they called the 鈥渟tar cluster,鈥� was found in 16 populations that lived in a very large section of Asia. Eight percent of the men they tested had this Y chromosome. If their sample was representative鈥�if it was!鈥攊t meant that 0.5% of the entire world had this Y chromosome. There had to have been selective pressure to make this happen, as random chance alone was much, much too improbable. But because of how small the chromosome is, it was unlikely that one of its genes provided a clear survival advantage. The reason this version of chromosome Y was so common must have been because one guy had been, well, very, very reproductively fit.
The scientists estimated that the most recent common ancestor of all these men, the granddaddy of this Y chromosome, lived in Central Asia about 1,000 years ago.
Thinking about it, they zeroed in on one strong possibility: Tem眉jin, better known as Genghis Khan, the barbarian warlord whose conquests are now the stuff of legends. He had five daughters and four sons from his senior wife, and many more with the junior wives he acquired through conquest. Let鈥檚 just say that his genes strutted about Central Asia a lot.
It could be this haplotype鈥� or this haplotype鈥� or this haplotype
At its height, the Mongol Empire, born of the unification of nomadic tribes under Genghis Khan, was so large, it is by the British Empire in terms of land area. Despite its importance, there is so much we don鈥檛 know about Genghis Khan himself. That famous of him? It has been referred to as an made by historians generations removed from the man himself. We have no description or illustration from the people who lived with him. And his body? It is still hidden.
The corpses of kings were believed to retain their godly power, so they were buried in secret in inaccessible places, often mountain sites, that were thought to be close to heaven. Genghis Khan鈥檚 final resting place has never been found, and not for want of searching. A decade ago, over 10,000 online volunteers spent a combined total of three-and-a-half human years looking for anything that might give away Khan鈥檚 burial. A National Geographic expedition was launched to explore 55 sites of interest following this virtual search. Tem眉jin remains elusive.
In 2004, five graves were discovered in Tavan Tolgoi in Eastern Mongolia and the artefacts they contained, as well as the wood used for the coffin, strongly pointed toward a Mongolian imperial family, specifically Genghis Khan鈥檚. Scientists but the Y chromosome they found in the men was not the one with the star cluster. Were these men members of Tem眉jin鈥檚 family or were they unrelated generals of his? The scientists did not know.
Another group of researchers investigated that claims to be the descendants of Toghan, Genghis Khan鈥檚 sixth son. Their Y chromosome is different from the one described in the Zerjal paper and the Tavan Tolgoi excavation.
To confuse the situation even more, a revisited the Zerjal paper a few years ago. The problem with a study in which you test the DNA of a population is that you can鈥檛 test everyone. You have to pick a sample and hope that this sample is representative. The Chinese team broadened their sample. Whereas Zerjal had looked at 2,123 men, this new team looked at over 18,000 individuals from a broader region of Central Asia to see what was really going on. In gaining a more refined picture, they saw that this haplotype wasn鈥檛 1,000 years old; it was about 2,600 years old, older than Genghis Khan himself. It probably belonged to the ancestor of all Mongolic-speaking people. They conclude their paper by writing that none of the people who carried this Y chromosome can trace their genealogy to Genghis Khan, and none of his self-claimed direct descendants carry it either.
So this common Y chromosome, at the origin of the claim that half of a percent of all men on Earth are descendant from Genghis Khan, predates the warlord himself. Being older than 2,000 years, it had plenty of time to spread among the many tribes of Central Asia, and to further scatter when the region became the heart of the Silk Road, bridging Europe and Asia and facilitating a lot of genetic commingling.
We may not be direct descendants of Genghis Khan, but we all bear within our cells the migratory path our ancestors took out of Africa. As for Tem眉jin, his face, bones, and DNA itself remain hidden from us.
Maybe one day a new discovery will enable us to trade in part of his legend for some cold, hard facts.
Take-home message:
- A 2003 study found that a large number of men carried a Y chromosome that seemed to have come from Central Asia 1,000 years ago, leading to the speculation that it was Genghis Khan鈥檚
- A more recent study using a much larger sample of men from a wider geographic area shows that this Y chromosome actually predates Genghis Khan by a millennium
- Genghis Khan鈥檚 burial site has yet to be found, so we do not have DNA on him. A number of Y chromosomes have been speculated as belonging to him
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