Ancient DNA reveals pervasive directional selection across West Eurasia, Nature acknowledges:
Ancient DNA has transformed our understanding of population history, but its potential to reveal as much about human evolutionary biology has not been realized because of limited sample sizes and the difficulty of distinguishing sustained rises in allele frequency increasing fitness — directional selection — from shifts due to migrations, population structure, or non-adaptive purifying or stabilizing selection. Here we present a method for detecting directional selection in ancient DNA time-series data that tests for consistent trends in allele frequency change over time, and apply it to 15,836 West Eurasians (10,016 with new data). Previous work has shown that classic hard sweeps driving advantageous mutations to fixation have been rare over the broad span of human evolution. By contrast, in the past ten millennia, we find that many hundreds of alleles have been affected by strong directional selection. We also document one-standard-deviation changes on the scale of modern variation in combinations of alleles that today predict complex traits. This includes decreases in predicted body fat and schizophrenia, and increases in measures of cognitive performance. These effects were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past. We estimate selection coefficients at 9.7 million variants, enabling study of how Darwinian forces couple to allelic effects and shape the genetic architecture of complex traits.
…and yet we remain human after millions of years.
Well, we certainly haven’t ascended to become beings of pure energy.
LOL.
Wanweilin says:
Biological advantage of sentience can be expressed simply as “upgrade from adaptation only via slow hardware evolution to much faster software evolution”.
Evolution of memeplexes via mutation and branching off (ethnogenesis) is a replacement for evolution of subspecies via mutation and branching off.
Once it hit tool building stage, evolutionary pressures simply had very little effect. Which is why humans remain mostly good old cromagnon. With very few dead ends in areas of high radiation and tough environment, like bushmen: amazing in their terrain, but downgraded nearly to useless souvenirs outside it.
Which is why trekkie types with their “planet of hats” meme are utterly retarded. In strict terms, it’s a failure to take advantage of sapience.
And so is the Protestant narcissism underlying the trekkie idiocy, of course.
Speaking of Nicaragua, even the milder Catholic narcissism that gave birth to this proved to be not much better in a great natural experiment. The “total unity” and “colorblindness” were tried in colonial Mesoamerica, and worked right until their celebrated obsolescence of good fences somehow resulted in failure of good neighborhoods and a bloodbath.
T. Beholder: “Once it hit tool building stage, evolutionary pressures simply had very little effect.”
No offense, but literally what the fuck are you talking about?
Jim says:
Well, what was so special about Homo Sapiens Foo that they should become The Next Big Thing on the planet?
At first, they are just another bunch of naked primates, with inherent disadvantages of big brain (needs more food, and not only glucose) in big head (leads to more fatalities by birth).
So there seem to be 3 big thresholds to clear:
1. Manifest enough of advantages over the next bunch of monkeys to consistently more than compensate for those disadvantages. That’s what it takes to keep a new trait, biologically speaking.
2. Be resilient. Adaptations are needed because something always happens. If only because weather patterns oscillations on ~100-1000 years scale exist.
Those who adapt and survive while the competitor can only die out or migrate would naturally own the changed territory without one more competitor. Which leads to the next big step.
3. Actively expand into new biomes.
There’s a bootstrap problem: to be optimized for new conditions by basic evolutionary pressures, a stable population should already survive there for a long while.
So (1) is why modern Homo Sapiens Sapiens is little different from a Cromagnon man. But (3) was the real test to become The Next Big Thing: jump to more than surviving yet another bad year or doing the same slightly better. It almost certainly took more than clever monkeys learning new tweaks of simple tricks from each other. The earliest qualitatively new capability known to us were tools, using knife and fire. So it makes sense that’s what expansion leveraged: making things that increase resilience.
T. Beholder, your foundational premise that “modern Homo [s]apiens [s]apiens is little different from Cro[-M]agnon man” is farcical on its face. There are enormous differences in physiology, psychology, sociality, and capability between H. sapiens sapiens subspecies today. The descendants of Aztecs reliably fail to manipulate electricity when proven blueprints for working systems along with every foundational component are made available to them, let alone the descendants of Bantu, who proactively dismantle working water pumps given to them for free. The most indigenous of the Indian subcontinent’s subspecies’ apex predator is the train, a stealthy, unpredictable beast. Even the differences between the Germans and the Poles, two nations occupying adjacent patches of the same European continent, are vast: per George W. Bush lookalike George Friedman of Stratfor, the last three-quarters of a century of the United State’s foreign policy have been oriented in very large part toward guaranteeing the continuing geopolitical separation of the Germans from Russian resources, Poles relegated to a footnote at best. Ironically, the United State may not have been able to successfully suppress the Germans of Germany without its own German transplants in America.