It has only been rather recently that researchers have found that Neanderthals never truly died out. Instead, they hybridized with some homo sapien populations especially in Europe. Their DNA contribution is somewhat small in percentage terms but still prominent in both European and Asian populations and negligible to nonexistent in many sub-Saharan African populations. The typical Caucasian has between 1% and 5% Neanderthal DNA.
The 23 and Me DNA test results include the Neanderthal percentage. I haven’t taken it myself but my aunt (my father’s full sister) did and her Neanderthal percentage came out at the somewhat high end at 4.1%. I will take one myself soon but I assume the results will be similar.
However, I am not sure exactly what they are referring to with that number. Roughly 4% may not sound that high but it could be really significant depending on what it refers to. After all, all hominids share well over 90+% of their DNA already. Chimps and humans share roughly 96% for example.
What does this specific result compare and how does that equate to other measures of genetic similarity between species like chimps?
Questions like this come up here from time to time. Even the sharing 94% with chimps is misleading. We share a lot more DNA than that with all mammals.
The worst is when someone says you share 50% of your DNA with a parent.
Only a select few key genes are tested and compared, not overall DNA. This gets glossed over very, very badly.
These are basically just numbers on an arbitrary scale that no one ever bothers to clearly explain to ordinary folk. I.e., sharing 20% vs sharing 10% means you have more in common. That’s basically the best you can say.
You need to be deeply involved in the business/trade/sport/science to even have any idea of what’s being discussed.
Trying to reduce it to ‘sound bite’ level renders it meaningless.
Kinda like seismology and ‘Richter Scale’ - the Richter Scale has been obsolete for decades, but when a jolt is large enough for a reporter to call, they ‘convert’ the real info back to Richter because that is what the great unwashed know.
It’s not beyond understanding the basic idea. They look at specific mutations at specific locations in your DNA strand that have been found in Neanderthal DNA but not in populations of Homo Sapiens in areas that had no contact with Neanderthals.
The 23/me site looks at 84 sites for 42 markers and uses some math of their own invention to decide what sort of percentage it all works out to.
The biggest problem with reducing it all down to some sort of number is that genes are not simply data points. We understand the specifics of some of them, but most of them not so much.
If they find matches, then it’s probably likely there is a Neanderthal deep in your family roots. “How much?” A few genes, at best. Very hard to say if it matters in any non-philosophical way.
I was at a party in WA state. And the conversation evolved to who had the highest percentage of Neanderthal. Lots of bragging, as if to say, I am the most primitive or more natural. Very entertaining.
I assume this means that if you could trace your pedigree back 3000 generations or so (before the interbreeding started) and classify the ancestral slots, that 4.1% of the ancestors (or rather ancestor slots) would be Neanderthal and 95.9% would be H. sapiens sapiens.
I suppose the analysis is based on mitochondrial DNA, since nuclear DNA as old as Neanderthals is very hard to recover and analyze.
Not sure that is correct. When someone says you are X% Neanderthal, they mean that X% of your base pairs are derived from Neanderthals, not X% of your genes. There might be hundreds (or more) of base pairs in any gene. I asked a similar question long ago, and that was how Colibri answered it.
I am no expert in these matters, but I’ve heard or read that most of the relevant Neanderthal genes might be related to the immune system, possibly granting resistance to diseases endemic to Europe at one time.
Which makes some sense - what would be preserved would be genes advantageous to those possessing them. Resistance to disease/parasites would definitely confer a reproductive advantage.
So the effects may be invisible to the naked eye. Some Neanderthals apparently had red hair, but the genes causing that in them are also apparently markedly different than in Sapiens making it a matter of convergent evolution and not a matter of inheritance from a common ancestor. It may be that Neanderthal contributions to modern humans have had zero effect on appearances and any coincidental resemblance is just that, coincidence.
I don’t think it’s most genes, and not everyone has the same Neanderthal genes. The latest studies show that about 20% of the Neanderthal’s total genome may be preserved in us modern humans, and if anything, it looks like that number is going to increase as more studies are done. We do see that some genetic material related to skin (color) is also seem to be Neanderthal in origin, for instance.
The “beaky nose” is, in theory, one form of cold adaption, pre-warming inhaled air. Of course, it is also vulnerable to things like frost bite.
Heavy beards in men might or might not have been a cold adaption. I don’t think we have any way to known how bearded Neanderthals might or might not have been. Or beards could simply be something sexually selected in humans (or, perhaps, selected against in some groups with sparse facial hair).
The “flat face” and epicanthal eyes folds of Inuit/Asians is another potential cold adaption, providing both more insulation for the facial muscles and a different amount of exposure to cold in the resulting profile. Of course, this adaption doesn’t pre-warm air quite as well as the “beaky nose”
The short limbs/long torso of Inuit/Arctic peoples is yet another cold adaption, one often seen in other arctic/high altitude critters. In fact, Neanderthals also had this trait, and to a greater degree than modern arctic natives.
So, there is more than one to adapt to cold, and it’s even possible that one or more evolved more than once in the human lineage.
Most of that stuff is speculative, at best. For example, the epicanthic fold seen in the eyes of many East Asian populations is also common in the !Kung San (Bushmen) peoples of southern Africa. If you had said “in hypothesis” in your first sentence instead of “in theory”, that would have been closer to the truth.
Many adaptations that work for extreme climates work for all extreme climates. It doesn’t negate the causality. Desert dwellers and snow dwellers both need to protect the eyes from extreme sunlight. Epicanthic folds are useful to both. Likewise, dry searing heat is as dangerous to lungs as dry freezing cold. Nasal passages help to temper both before air hits the lungs. The difference, of course, is that cold will bite off a prominent nose, so that adaptation is more of a detriment in cold areas.
Interestingly enough, people trying to survive in climates that they are not ancestrally adapted to may have resulted in the cultural concept of the “redneck” - white people of mostly northern European ancestry (e.g. British Isles, Scandinavia, Germany) doing agricultural work at latitudes much lower (e.g. in Georgia, Alabama, etc.) than their ancestors did, and thus getting sunburned.