Science Daily reported last week that Neanderthals left humans a genetic burden, which is having less offspring. Of course, these deleterious alleles only introgressed into non-African populations due to Africans not leaving Africa. This manifests itself today in birth rates within countries and between them based on the ethnic/racial mix. And (not) coincidentally, the areas with the highest rate of children are in sub-Saharan Africa.
The Neanderthals existed in small bands, so inbreeding was common. Due to this inbreeding, Neanderthals were more homogenous than we are today. When humans migrated out of Africa, they encountered the inbred Neanderthals who they interbred with. Harmful genetic variants acquired from Neanderthals are shown to reduce the fitness of populations with certain deleterious alleles. There are of course tradeoffs with everything in life. Increased intelligence and being better able to weather the Ice Age, among numerous other factors, were positive things gained from interbreeding with Neanderthals. Negative effects were the acquisition of deleterious alleles which still persist today in non-African hominids. These deleterious alleles decreased biological fitness which manifests itself in the birthrate of Eurasian populations throughout the world (the Germann and Japanese birthrate is 1.3 for reference).
Harris and Nielson also hypothesize that since Neanderthals existed in small bands that natural selection was less effective, allowing for weakly harmful mutations to pass on and not get weeded out over the generations. However, when introduced back into humans these effects become lost over time due to a large population with natural selection selecting against the deleterious Neanderthal alleles. Using a computer program, Harris and Nielson quantify how much of a negative effect the Neanderthal genome had on modern populations. The conclusion of the results was that Neanderthals are 40 percent LESS genetically fit than modern humans.
The researchers’ simulations also suggest that humans and Neanderthals mated more freely, which leads more credence to the idea that Neanderthals got absorbed into the Homo Sapien population and not mostly killed off. The estimation for Neanderthal DNA in modern hominids from the simulation was around 10 percent, which then continued to drop as the Neanderthal-Homo Sapiens hybrids interbred with those who hardly had any Neanderthal DNA. More evidence also shows that the percentage of Neanderthal DNA was higher in the past in Eurasians as well. Which makes sense since Asians have on average 20 percent more Neanderthal DNA than Europeans due to a second interbreeding event.
However, Harris and Nielson end up concluding that non-Africans historically had a 1 percent loss in biological fitness due to Neanderthal genetics. Moreover, a better immune system came from Neanderthal genetics. Skin color is another trait inherited from Neanderthals as well.
Along with the acquisition of deleterious Neanderthal alleles, early Eurasians also encountered the same environment as the Neanderthals. Those selection pressures, along with interbreeding due to small bands lead to a decrease in the number of children had. Fewer children are easier to care for as well as show more attention to. All of these variables in that environment lead to fewer children produced. It’s a better evolutionary strategy to have fewer children in more northerly climes than in more southerly ones due to the differing selection pressures. Environmental effects are also one reason why birthrates are lower for populations that evolved in northerly climes (Neanderthals and post-OoA hominids). Harsh winters lead to a decreased population size, as evidenced by the Inuit and Eskimoes, which their low population size didn’t allow for selection for high IQ despite having the same brain size as East Asians.
I couldn’t help but think that, yet again, for the second time in two weeks, one of JP Rushton’s theories was confirmed. This confirms one of the many variables of Rushton’s r/K Selection Theory. Just like I covered how Piantadosi and Kidd corroborated Rushton’s theory of brain size and earlier child birth. Neanderthals had bigger brains than we do today, and knowing what we know about the correlation between IQ, brain size and early childbirth, I would assume that Neanderthals also had earlier childbirths as well,.
Along with these deleterious gene variants from Neanderthals, other variables that contribute to the decline in Eurasian populations also include higher IQ as well, as JP Rushton says, is an extreme way to have control over their environment and individuality. These traits are seen in higher IQ populations in comparison to lower IQ populations. We could also make the inference that since Eurasian children have bigger heads, that multiple childbirths would be taxing on the Eurasian woman’s birth canal while it would be less taxing on the African woman’s.
This study also shows that Neanderthals also had less offspring due to being more intelligent. They had bigger brains than we do today, and since we know that higher IQ is correlated with fewer children conceived, we can say that they were pretty damn smart (they buried their dead 50,000 years ago. There was also a recent discovery of a 176,500-year-old Neanderthal constructions in a French cave). A main cause for the current trend in birthrates in Eurasian populations is due interbreeding with Neanderthals. These events also attributed more to the decline of the Neanderthals.
Deleterious Neanderthal alleles are yet another reason for lower Eurasian birthrates, which shows = that the current trend currently happening in the world with these populations is natural and evolutionarily based. I’ve said a few times that by showing positive things to women on television will increase the white birth rate, with Rushton cites National Socialist Germany as one example. By showing women happy with children, this lead to a massive boom in the German population. To ameliorate the effects of low natural birth rates, these positive things need to be shown on television to women to start to reverse the effects of low natural childbirths.
It’s been a great month for Rushton’s theories, with two of them being corroborated in one month. It’s only a matter of time before the denial of human nature is completely discarded from modern science. As the data piles up on human genetic diversity we will not be able to deny these clearly evident factors any longer.