“If you were to compare two random modern human chromosomes, you’d see a difference every thousand base pairs…[comparing modern humans with] Neanderthals, you’d see a difference once every 750 base pairs.”
– Encyclopaedia Britannica
According to the figures in the quote, there is only approximately a 25% difference, chromosomally, between H. Sapiens (you and me) and H. Neanderthals, and (depending on the source) that difference amounts to upwards of 2-3% of your genes if you are of European descent or as much as 6% if your folk hail from southeast Asia and Oceania; only if you’re sub-Saharan African do you escape having any Neanderthal in your family tree and, thus, in your DNA.
Now, the “H” preceding Sapiens stands for “Homo”, which means “man, human” and “Sapiens” means “modern [man/human]”, the only existing species of humans; the “H” in front of Neanderthal also stands for man/human, only they are not Sapiens because they no longer exist as a species. And we (and they) are not the only humans to have walked the Earth – others (called “archaic” meaning old, or older humans) include at least 13 types dating back 2.5 million years or so.
Neither space nor your or my time allows for a detailed description of any of those archaics, or where they first came from, or where they fit into the human family tree, or if and when and where to they emigrated out of Africa. Suffice it to say that (again, depending on the source) Neanderthals date back some 250,000 years ago in all of Eurasia, finally disappearing approximately 30,000 years ago; Sapiens appeared in Eurasia about 100,000 years later. Which means we and they lived side-by-side, from what is now England through all of Europe and the Middle East, for upwards of 70,000 years. As humans, our people (Sapiens) have lived alone as the only humans on Earth for only the last 30,000 years.
And the first interbreeding between Sapiens and Neanderthals may have taken place in what is now Israel only 55,000 years ago, based on fossil remains.
Why, one might ask, would they? Sapiens bred with Neanderthals? Those ape-like hairy, brutish, grunting, knuckle-dragging, club-swinging cavemen?
Would you be surprised to learn that they appreciated music as much as we, and that it was they who first created the tuba and flute? Or appreciated art, and painted pictures on walls thousands of years before we did? Also practiced medicine and healings? Also buried their dead with food, tools, weapons and household goods, which indicates religion and belief in an afterlife? Had the same vocal cords we have (unlike any previous “archaic” human) and thus were capable of the same kind of speech, language? Weren’t any hairier than we? And walked just as upright?
Would you be surprised that – in fact – if you put one in a coat and tie, and on any modern city street, no one would see anything different from any other person? Other than being a few inches shorter, maybe slighter more stocky and muscular, with marginally more pronounced brow ridges, than the average man, but not so much as to be eye-catching?
(For those who are Bible believers, currently the most widely accepted creationist view of the Neanderthals is that they were probably one of the tribes that departed from Babel in the dispersion, 106 years after the Flood.)
Obviously, neither they nor we saw one another as so different and therefore undesirable when the urge to mate arose on occasion. They have also been found buried alongside of us in the same grave, which indicates some kind of close relationship.
So why aren’t they still here?
Lots of different theories about that. They thrived in cold weather, during the last Ice Age, and maybe after the thaw and warming when the flora and fauna and landscape changed they were unable to adapt. Or by slow starvation, as their physiology didn’t allow them to throw spears as well as we could, or to run as far and for as long as we, and couldn’t compete in the hunt? Or, just maybe, our ancestors were just like us when it comes to settling lands already occupied – we simply exterminated them and took what was theirs because we wanted it (that’s a very likely scenario, as the last Neanderthals were found in southern Spain, in Gibraltar, apparently forced there, where there was no where to go except into the sea. In Europe, ancient DNA has identified waves of migrations into the continent, in which groups of people serially replaced, or nearly replaced, the local population, with Sapiens being the last “wave” just after Neanderthal’s).
But I think the most likely reason is also physiological, and sexual.
According to https://m.phys.org/news/2016-04-modern-men-lack-chromosome-genes.html:
“The Neanderthal Y chromosome genes could have simply drifted out of the human gene pool by chance over the millennia. Another possibility…is that Neanderthal Y chromosomes include genes that are incompatible with other human genes…Indeed, one of the Y chromosome genes that differ in Neanderthals has previously been implicated in transplant rejection when males donate organs to women.
“Several Neanderthal Y chromosome genes that differ from those in humans function as part of the immune system. Three are “minor histocompatibility antigens,” or H-Y genes, which resemble the HLA antigens that transplant surgeons check to make sure that organ donors and organ recipients have similar immune profiles. Because these Neanderthal antigen genes are on the Y chromosome, they are specific to males.
“Theoretically…a woman’s immune system might attack a male fetus carrying Neanderthal H-Y genes. If women consistently miscarried male babies carrying Neanderthal Y chromosomes, that would explain its absence in modern humans. So far this is just a hypothesis, but the immune systems of modern women are known to sometimes react to male offspring when there’s genetic incompatibility.”
So while a male child (Y chromosome) might be aborted, a female child (X chromosome) wouldn’t, necessarily, and that’s how you come by your Neanderthal genes – blame your mother who passed down your X chromosome (X+Y= son, X+X= daughter) from her mother, and her mother on back to that Neanderthal-Sapiens coupling you are a product of.
And to finally answer the question, “Did Neanderthal Really Disappear?”
No. At least, only in part. Just look in the mirror.
As an aside: We share 99.7% of the same genome with Neanderthals. We share 99.8% the same with Chimpanzees. Obviously, some of the difference between us and the Chimps is in those genes that determine sexual compatibility for offspring. What if the Chimp’s and the Neanderthal’s had been reversed? A different type of hybrid? Just a thought. Look up my post of Jan. 27, 2017, “Stirring the Genetic Pot, Part II” for that possibility in the future.