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By all accounts, Genghis 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 everybody you know who you're great, great, great, add, like, 25 more great-great-grandfather was, let's do a deeper dive into how this idea came about and how likely it really is.
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 on to 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 a thousand 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 four of his 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 describe 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 are 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 hotspot 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 describe as the likely descendants 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 are 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 that 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.