Tuesday, October 11, 2016

Evolution: Humans Are Rapidly Changing

Over the past 10,000 years, human evolution has occurred a hundred times more quickly than in any other period in our species’ history. The new genetic adaptations, some 2,000 in total, are not limited to the well-recognized differences among ethnic groups in superficial traits such as skin and eye color. The mutations relate to the brain, the digestive system, life span, immunity to pathogens, sperm production, and bones—in short, virtually every aspect of our functioning.

Many of these DNA variants are unique to their continent of origin,"It is likely that human races are evolving away from each other. We are getting less alike, not merging into a single mixed humanity....
We aren't the same as people even a thousand or two thousand years ago. Almost every trait you look at is under strong genetic influence."

"During the span of the past 35,000 years, teeth are getting smaller, skull size is shrinking (as brains become more efficient) ....! With newly emerging genetic data from stunning advances in sequencing and deciphering DNA in recent years, scientists had begun uncovering, one by one, genes that boost evolutionary fitness. These variants, which emerged after the Stone Age, seemed to help populations better combat infectious organisms, survive frigid temperatures, or otherwise adapt to local conditions. And they were popping up with surprising frequency."

"...Why might evolution be picking up speed? Because, in a large population you don’t have to wait so long for the rare mutation that boosts brain function or does something else desirable.... in reviewing the demographic data, ten  thousand years ago, there were fewer than 10 million people on earth. That figure soared to 200 million by the time of the Roman Empire. Since around 1500 the global population has been rising exponentially, with the total now surpassing 6.7 billion. Since mutations are the fodder on which natural selection acts, it stands to reason that evolution might happen more quickly as our numbers surge.... this was nothing new to animal breeders of the 19th century. Darwin himself emphasized the importance of maintaining a large herd for selecting favorable traits.”

"The logic behind the notion was undeniably simple, but at first glance it seemed counterintuitive. The genomes of any two individuals on the planet are more than 99.5 percent the same. Put another way, less than 0.5 percent of our DNA varies across the globe. That is often taken to mean that we have not evolved much recently, but keep in mind that the human and chimp genomes differ by only about 1 to 2 percent—and nobody would call that a minor difference. None of this conflicts with the idea that human evolution might be accelerating.”

[There is much more.....]

Map: Y-DNA Human Migration (Haplogroups):