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Here’s a brief accounting of how modern humans came to bear ancient DNA from the Neanderthals.
We split from chimpanzees 5-7 million years ago.
Then around 2-2.5 million years ago, the first hominins (our earliest ancestors), started appearing in current East Africa.
Homo habilis and Homo erectus were among the first human species intelligent enough to develop tools. The latter was the first to learn how to use fire.
About 1.75 million years ago, Homo erectus started migrating out of Africa to Eurasia seeking more food and favorable climate. Some of the first countries they settled in include China, Pakistan and Indonesia.
Homo erectus then evolved into Homo neanderthalensis, or what we commonly refer to as the Neanderthals, who appeared 200,000-300,000 years ago.
The Neanderthals lived in Eurasia. They went extinct quite recently; around 40,000 years ago.
A few thousand years just before the Neanderthals went extinct, Homo sapiens (that’s us) started migrating out of Africa where they had most likely evolved from Homo heidelbergensis.
They came to Eurasia where they found Neanderthals already living there.
Surprisingly, the two species managed to cohabit peacefully and even had sex!
It is thought that over the course of 2,600 to 5,400 years, the Neanderthals (who were already dwindling even before modern humans came along) gradually assimilated into Homo sapiens.
The sexual relations between modern humans and Neanderthals means that the latter’s DNA survived long after they went extinct.
Today, modern humans have between 1-4% Neanderthal DNA. Non-Africans have the greatest percentage of it while some Africans have around 0.5-1% (most likely due to back migration).
Currently, only two ancestry DNA testing services include Neanderthal DNA analysis in their reports: 23andMe and the Genographic Project (via their Geno 2.0 kit).
The Geno 2.0 test results will tell you whether you have any Neanderthal DNA and what percentage.
The 23andme Neanderthal DNA also does the same thing.
They look for more than 2,000 genes in your genome that are known to have originated from Neanderthals. The report will tell you how many Neanderthal gene variants they found.
But how do these companies know which genes are Neanderthal. Did someone go back in time to test Neanderthals and get their DNA to compare to that of modern humans?
Well, sort of.
Over the years, archeologists have found Neanderthal skeletons in various locations around the world. Geneticists then try to extract any surviving DNA from these bones.
Researchers also hunt for ancient DNA in caves where skeletons have been found.
By analyzing this DNA, they have found distinct gene variants that are common in both Neanderthals and Homo sapiens.
Note: Beyond 23andMe or the Genographic Project, you have two other options to analyze your Neanderthal DNA. You can upload your raw data to GEDMatch or take a test with FTDNA and see if you match one of the Ancient DNA samples in their database. If you do, you can join the Ancient DNA project.
Our dalliance with the Neanderthals had good and bad results. They passed along some good genes which allowed Homo sapiens to spread around the world and conquer it.
But they also gave us some nasty genes that are involved in health conditions like type 2 diabetes, Crohn’s disease and the HPV16 STD. Smoking addiction is also thought to be linked to Neanderthal DNA.
To be fair, we gave them some pretty awful genes as well, introducing diseases like tuberculosis and stomach ulcers that may have hastened their extinction.
But that’s a general view of how Neanderthal DNA has affected modern humans. When you are talking about individuals, your Neanderthal DNA percentage doesn’t mean much.
For one, most non-Africans have at least 1% Neanderthal DNA. So we are all suffering roughly the same effects of having Ancient DNA.
It probably doesn’t make a difference whether you have 2% Neanderthal DNA or 4%.
But as with everything scientific, and especially when it comes to genetics, things could change as we learn more. We might discover that the amount of ancient DNA in individuals has a bigger impact than originally thought.
But for now, a Neanderthal DNA test is purely for fun and to appease curious minds.
I'm just another amateur genealogist investigating my American-Scots-Irish lineage. I built MyFamilyDNATest.com after buying all of the leading DNA tests to discover everything I could about my family history. Hopefully, this site will save you time and demystify the emerging science of DNA-based genealogy, for your family project.