Tag Archives: lactose intolerance

How Fast Are Humans Evolving?

paleo diet, Steve Parker MD,calcium, osteoporosis

I’m guessing she’s northern European, perhaps Irish

Most paleo lifestyle proponents think that, genetically speaking, those of us living today are pretty much the same as our ancestors living 50,000 or even 200,000 thousand years ago. That may not be the case.

Conventional Wisdom

The traditional view of the rate of human evolution’s is articulated by Artemis P. Simopoulos, who was with The Center for Genetics, Nutrition and Health in 2009 when he wrote: “The spontaneous mutation rate for nuclear DNA is estimated at 0.5% per million years. Therefore, over the past 10,000 years there has been time for very little change in our genes, perhaps 0.005%. In fact, our genes today are very similar to the genes of our ancestors during the Paleolithic period 40,000 years ago, at which time our genetic profile was established.”

Evolving Thought

 

On the other hand, the experts are debating now whether the pace of human evolution has accelerated over the last 10,000 years. The iconoclasts say it has. For example, remember that most mammals lose the ability to digest milk after they’ve been weaned off the teat in early life: they lose the lactase enzyme that allowed them to digest milk sugar (lactose). That’s why lactose intolerance is so common among adult humans—only a third of us worldwide can digest milk. Five or 10,000 years ago, a genetic mutation occurred that allowed those possessing the gene to consume and digest milk. So a whole new source of food for adults opened up: dairy cattle. Would that have conferred a survival advantage? You bet. We have evidence that the milk-digesting mutation spread fairly quickly since its appearance. But it hasn’t spread across the globe uniformly. The ability to digest milk in adulthood—called lactase persistence—is less than 40% in Greece and Turkey, but higher than 90% in the UK and Scandinavia.

Another oft-cited example of rapid and recent human evolution is the appearance and spread of blue eyes starting six to 10,000 years ago. Everyone with blue eyes today apparently has a common ancestor that had a gene mutation back then, when everybody had brown eyes.

For more information on the “rapid evolution” idea, check out the writings of Gregory Cochran, Henry Harpending, and John Hawks. Also consider a new book by Nicholas Wade, “A Troublesome Inheritance: Genes, Race, and Human History.” Wade is a science writer for the New York Times.

Steve Parker, M.D.

White Skin in Europeans Only Took Off 6,000 Years Ago

…according to an article at Science magazine. Europeans 10,000 years ago didn’t look much like those of today.

When it comes to skin color, the team found a patchwork of evolution in different places, and three separate genes that produce light skin, telling a complex story for how European’s skin evolved to be much lighter during the past 8000 years. The modern humans who came out of Africa to originally settle Europe about 40,000 years are presumed to have had dark skin, which is advantageous in sunny latitudes. And the new data confirm that about 8500 years ago, early hunter-gatherers in Spain, Luxembourg, and Hungary also had darker skin: They lacked versions of two genes—SLC24A5 and SLC45A2—that lead to depigmentation and, therefore, pale skin in Europeans today.

But in the far north—where low light levels would favor pale skin—the team found a different picture in hunter-gatherers: Seven people from the 7700-year-old Motala archaeological site in southern Sweden had both light skin gene variants, SLC24A5 and SLC45A2. They also had a third gene, HERC2/OCA2, which causes blue eyes and may also contribute to light skin and blond hair. Thus ancient hunter-gatherers of the far north were already pale and blue-eyed, but those of central and southern Europe had darker skin.

Pale skin may be advantageous in northern latitudes because it allows production of more vitamin D.

The article also discusses European evolution of lactose tolerance and height. The ability to digest milk in adulthood apparently didn’t spread through Europe until about 4,ooo years ago.

RTWT.