The Decline of Human Genetic Diversity (in Europe)

Diversity is a hot topic in anthropology, and is something that is studied culturally, archaeologically, linguistically, and biologically. I’ll be only addressing the latter of the four sub-disciplines of anthropology in this morning’s post, because examining the changes in genetic diversity of humans ultimately affects the other three fields.

The results of a mtDNA study spanning Europeans from five different periods of history, all the way back to 300 AD to the present day, has been published in Biology Letters. The title, “Ancient human mtDNA genotypes from England reveal lost variation over the last millennium,” gives you a clue as to what was concluded, the abstract gives a bit more,

“We analyzed the historical genetic diversity of human populations in Europe at the mtDNA control region for 48 ancient Britons who lived between ca AD 300 and 1000, and compared these with 6320 modern mtDNA genotypes from England and across Europe and the Middle East. We found that the historical sample shows greater genetic diversity than for modern England and other modern populations, indicating the loss of diversity over the last millennium. The pattern of haplotypic diversity was clearly European in the ancient sample, representing each of the modern haplogroups. There was also increased representation of one of the ancient haplotypes in modern populations. We consider these results in the context of possible selection or stochastic processes.”

I’ve bolded what I consider the most informative section.

So, about 1700 years ago, three out of every four individuals belonged to a different haplotype. But now in modern Europe, the number is only one in three.

Why’s that? What are stochastic processes?

Stochastic is a fancy scientific way of saying random. That ultimately trickles down to mean that the loss in genetic diversity is because of a lot of things. Makes sense, a lot has happened in Europe in the last 2,000 or so years. Epidemics like the plague, which decimated populations, are one of the many random processes that narrow down genetic diversity. Other processes, that are more cultural than biological, like wars and genocide, are definitely another factor to consider in loss in genetic diversity.

As I was reading this, this question popped in my head, “Isn’t what the researchers concluded basically what that whole “survival of the fittest” thing does?” Yes and no, selective processes like the plague weeded out people who didn’t have an allele of the gene CCR5, called “delta 32.” And the no, goes back to diversity is itself a survival trait in a population; in other words a population comes close to zeroing in on a single genotype is vulnerable.

Nonetheless, the results are intriguing and a bit Eurocentric. I guess that’s why it got published in a Royal Society journal. I wonder how will the influx of immigrants from the Middle East to Europe shake up the European gene pool? Anyone know of any studies that address the genetic impact of Middle Easterners in Europe?

2 thoughts on “The Decline of Human Genetic Diversity (in Europe)

  1. Strictly speaking:

    “Stochastic is a fancy scientific way of saying random”

    isn’t true. Let me give an example: if I go to practice shooting free throws in basketball, where the ball goes is the result of a stochastic process but NOT a random one. (I am not THAT bad of a shooter!) A stochastic process has a random element to it, but it really isn’t random.

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