Science was Wrong, Africans Have Neanderthal DNA Too
It's time to correct past mistakes
Hiya!
It was once thought that all modern European and Asian humans have at least some Neanderthal DNA. Many Asians, especially Melanesians, also have Denisovan DNA — another Human species that coexisted with Neanderthals and us.
African populations, however, were left out of the equation due to techincal issues and because experts assumed ancestral African populations and Neanderthals were geographically isolated from each other at the time. Then in January 2020, researchers learned such assumptions were a mistake.
Interbreeding
A little over a decade ago, in 2010, researchers mapped the whole Neanderthal genome and published their findings for the first time. Since then, it’s been thought that all European and Asian homo sapiens have about 2 percent Neanderthal DNA — and many Asian, especially Melanesians, also have up to 6 percent Denisovan DNA.
Let’s just say H. sapiens interbred a lot with other human species. This fact adds weight to a 2021 study suggesting interbreeding with us played a larger role in the Neanderthal extinction than violence between species. And knowing all of this makes it seem obvious that everyone alive today likely has trace amounts of other human species, especially Neanderthals, in our DNA.
Yet, African populations were largely believed not to have any traces of Neanderthal. The reason was that none was found when researchers compared the Neanderthal genome with five modern human genomes — from China, France, Papua New Guinea, southern Africa, and western Africa.
Since then, many models for tracing Neanderthal interbreeding relied upon the “reference population” method — genomes from a group thought not to have any Neanderthal DNA — such as African populations. Though, of course, this assumption seems pretty biased and limits the potential for further analyses of connections between Neanderthals and people of African descent.
Thankfully, technology has advanced, and now researchers developed a new method that confirms that people of African descent do actually have traces of Neanderthal DNA too. They just may have gotten it a bit differently.
The Study
A geneticist at Princeton University and author of the study published in the journal Cell, Joshua Akey, created a new method that found modern African populations have Neanderthal DNA too.
The method Akey and his team developed is called IBDmix — named after the genetic principle, “identity by descent” (IBD). The IBD is a DNA section shared between two people that represents a shared ancestor. The length of an IBD segment gives experts a good idea of how long ago the individuals shared a common ancestor. In an article by Princeton about the discovery, they explain:
“For example, siblings share long IBD segments because their shared ancestor (a parent) is only one generation removed. Alternatively, fourth cousins share shorter IBD segments because their shared ancestor (a third-great grandparent) is several generations removed.”
The team of researchers used the IBDmix method to search for and locate Neanderthal DNA within human genome. Then to distinguish between segments that look like Neanderthal DNA because we once shared a common ancestor around 500,000 years ago versus the segments that appear similar because of interbreeding within the last 50,000 years.
Unlike the “reference population” method, the IBDmix allowed the Princeton researchers to use the Neanderthal sequence itself to locate interbreeding or shared ancestry information rather than rely on biased or incomplete referenced information about populations.
During the study, Akey and his team used the genomes of 2,504 people — far more than the five samples used before — which came from the 1000 Genomes project. The genomes included East Asian, European, Southern Asian, American, and northern African individuals.
Amazingly, Akey discovered at least 17 million base pairs of African genomes are Neanderthal. For reference, that’s about a third of the amount the team found in Europeans and Asians.
The researchers believe these results not only correct previous mistakes and bias that Africans are exempt from having Neanderthal DNA, but it also changes previous assumptions regarding the migration of homo sapiens out of Africa.
In an article by National Geographic about the results, Akey explains that when it comes to early H. sapiens migration, “there’s this idea that people left Africa, and never went back.” Though clearly, these results, along with plenty of previous studies, indicate that migration was far less linear than once assumed.
Odds are likely that our migration from Africa was far less linear than science would prefer. H. sapiens likely migrated North, then crisscrossed back and forth. Even if ancient African populations didn’t interbreed with Neanderthals directly, the Neanderthal genome would still be genetically passed down if a parent had Neanderthal DNA in them.
Bonus Info:
As a side note, Akey’s study using the IBDmethod discovered an additional unexpected finding. Turns out, previous assessment of only about 2 percent of Neanderthal DNA in Europeans was underestimated. Akey’s research suggests Europeans actually have 8 percent or less.
Perspective Shift
This knowledge opens new areas for further research. It’s becoming increasingly clear that our evolution as a species and our relationships with other humanoids are far less linear than we thought. If you think about it, it was kinda silly of us to assume such histories would be linear at all. I mean, aside from cycles, Nature isn’t exactly known for linear, well, anything.
I’ve written about Neanderthals and our 21 other ancient human relatives before. Keeping track of or mapping those lineages is complicated enough without tossing in the innumerable hybrid variations created through millennia of migrations, mixing cultures, and mating.
Now, with genetic analysis as a tool at our disposal, this melting pot of various human species calls for even more combinations and boosts the need to reevaluate the past even more carefully. This includes refraining from filling in any gaps with our ideas or modern views.
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