By all accounts, Ghengis Khan got around.

Not just around Eurasia, which he  conquered and ruled for decades. But, you know, like around.

We don't know for sure how many children he had, but historians suggest it was a lot. So many, in fact, that some studies  (and pretty much all of the internet) have claimed that a huge number of people in Central and East Asia today  are his direct descendants. But before you go around telling  everyone you know who your great-great-great-great, and add about  25 more greats, great grandfather was, let’s do a deeper dive into how this idea  came about, and how likely it really is. [♪ INTRO] Genetic change within a population  typically happens a few ways.

Natural selection and random  chance both juggle the frequency of gene variants and how likely they  are to show up in a given individual. Certain genes could also turn  up more frequently thanks to a prolific breeder passing  on their DNA at a high rate. Much like Genghis Khan was suspected to be doing.

So if we want to know how many of his  descendants are running around today, we have to trace the source of  genetic changes in human populations. The Y chromosome would be a  great place to start with this, because it’s passed on by a single parent and does not swap its DNA with its paired X chromosome. That makes it an exception compared  to autosomes, or non-sex chromosomes, which like to trade bits of genetic  material with their matching counterparts, just to keep things spicy when those  genes are passed onto offspring.

So unlike others, the Y chromosome  stays intact over many generations, making it relatively easy to use  to trace its ancestral origin. A 2003 paper looked at the DNA  variation in the Y chromosome of thousands of individuals from  Central Asia to the Pacific. And their results showed that  about 8% of their participants had the same Y chromosome haplotype.

This means they belong to the same broad group – their Y chromosomes might  not be totally identical, but they all come from the same ancestor. 8% is a lot, especially across such a large area. It’s something the researchers would be more likely to see if they were working  with a small, isolated population. But instead it was, like, most of Asia.

And their findings suggested a single lineage was responsible for those 8% of people. From there, the team used models  to consider population dynamics and genetic mutation, and long story  short they traced this haplotype to a probable common ancestor about  1000 years ago, likely in Mongolia. And then, they asked themselves,  who’s a person who lived around then who was incredibly reproductively successful and they came up with Genghis Khan.

After all, reigning from Eastern  Europe to the Sea of Japan is bound to have some lasting influence on civilization,  not just culturally, but also genetically. He’s known to have had many wives and  many, many concubines over the years, which some scholars say may  have numbered in the hundreds. That said, we don’t know how  many children he actually had, as only his four sons with his first  wife were designated as his heirs.

And the thing is, we don’t have any  way of knowing if this Y chromosome haplogroup is actually connected to  Genghis Khan because we don’t have access to his DNA, since his remains were buried  in secret and have never been found. Basically, the researchers were guessing. It was a decent guess, and credit where it’s due, it got their work plenty of  attention.

But, still a guess. Still, their research has been continually  referenced over the years as proof of the great Khan’s genetic legacy, and the  likelihood that you may be related to him. But a 2018 study challenged  this link to Genghis Khan.

They set out to take a closer look  at the Y chromosome group described in the earlier study, and compare it  to closely related Y-group lineages. They also ramped up the sample size  to over 18,000 from 292 populations, collecting new samples from  thousands of individuals on top of using previously  published Y chromosome sequences. Their results told a different story.

They determined this haplotype  was older than previously thought, originating nearly 2,600 years ago,  long before Genghis Khan was around. They also showed that people most  likely to be the true descendants of Genghis Khan belong to a different haplotype. They did this not just using DNA evidence, but historical records that described  where Genghis Khan sent his troops, including his kids but also  people he was not related to.

And the 8% haplogroup corresponded  with the not-related-folks. They concluded that the big Y  haplogroup instead represents the ancestral expansion of  the Mongolic-speaking peoples. So as one of the founder Y chromosome  lineages in Mongol peoples, its success is due more to overall expansion of Mongol populations than one  guy having a lot of kids.

But also, while the Y chromosome can  help us determine direct lineage, it does have its drawbacks. Y chromosome studies only trace  ancestry via a single-parent lineage, leaving out the other genetic half completely, so it can paint an incomplete  picture of relatedness. That said, when we’re not focused  solely on sex chromosomes, our genetic material can be harder to track because chromosomes recombine all over the place.

But there is a workaround. We can also trace ancestry by looking  at Identical by Descent or IBD regions. IBD regions are any single  piece of DNA that is passed down from a common ancestor without  being fully genetically reshuffled.

These IBD fragments get smaller  and more mixed up over generations, as they get split up and combined  back together in offspring. In the end we’re all made  up of a patchwork of IBDs, and they can tell a tale  of common distant ancestors as we look for shared patterns. A 2020 study rather ambitiously  attempted to trace the interrelatedness of all humankind using this technique.

Good on ya! Take on the big tasks! They compared about 17 million IBD fragments, tracing common ancestors across 200,000 years!

And what they found were nine  distinct human genetics regions. East and West Africa, Northern  Europe, the Arctic, East Asia, Oceania, South Asia, the  Middle East, and South America. And these populations shared way more IBD bits with each other than with  neighbors from other regions.

They also found that the center of Eurasia is the most genetically mixed  geographic region in the world. And this makes a lot of sense. For thousands of years, this central  region was a hot spot for extensive trading and migration as well as conquests between  otherwise distant and remote regions.

So even though gene flow is  relatively limited by geography, we still interbreed wherever we cross  paths, and our genes move around. Okay, back to Genghis Khan. These researchers did specifically look  for genetic evidence of the Mongol Empire through this middle Eurasia region, as well  as other areas they occupied at length.

They compared the DNA of Tatars, who  they described as the likely descendents of Mongols, to people living in the  Middle East, Russia, and Europe. And despite these regions  having been bordered or directly occupied by the Mongols at some point or another, modern Tatars were more closely related to European populations than those in East Asia. Now, using modern Tatars as their  Mongol DNA sample gets complicated, because even though the term Tatar  has historically been linked directly with the Mongol Empire, this may  not be an accurate account of their very complex history and ancestry.

But what the study did find was  that present-day Central Asia was comparatively very tightly  related to East Asian populations. Given that trading along the Silk Route  had connected Eastern Asia with the West since the second century, it makes  sense that Genghis Khan’s empire wasn’t showing up as the main genetic  influence between these regions. They were pretty connected already.

That said, for a time the Mongol Empire  controlled 16% of the total landmass of Earth, so their expansion did play a  major role in expediting trade exchanges between these regions, so they certainly  still get credit where credit is due. What the study was able to show is  that many groups of humans share IBD regions with many other groups of  humans, no matter where they’re from. That means, even if your  ancestors have largely stayed put, generation after generation, there’s  still a great chance that you share at least some IBD fragments with folks  from distant corners of the globe.

And it is especially likely that you share  DNA with someone living in Central Asia, since they’re the most likely  to be carrying genes from, you know, basically everywhere, whether  that’s South America or the Arctic Circle. We are all related, and we are all  especially related to Central Asia! In the end, none of these techniques  can tell you if you’re directly descended from Genghis Khan, given  that we don’t even have his DNA.

But they can tell you a lot about  the wide range of populations you share ancestry with, no matter  where in the world you are from. And at the end of the day, I guess  there is still a chance your DNA does in fact harbor some deep tie to Genghis Khan. But that’s not simply  because he had a lot of kids.

It’s because his empire existed  in a time and in a place where people traveled to and fro for centuries! All that is to say, humans are humans. There’s nothing that can truly wall  us off into separate distinct groups because we have such a rich genetic history, woven together across the globe  over hundreds of thousands of years. [♪ OUTRO]