DNA Lactose Surprise? Not to Me.

Big news spreading around the scientific world is an article that isn't even available yet. It's a pre-print - a copy circulated before the official print date - of "Absence of the Lactase-Persistence associated allele in early Neolithic Europeans" by J. Burger, M. Kirchner, B. Bramanti, W. Haak, and M. G. Thomas.

Note: I've edited this post to make the proper link to the abstract available.

Proceedings of the National Academy of Sciences site.

With the recently acquired ability to study human DNA and compare it to DNA taken from bones, scientists have a virtual time machine that can study how humans have changed, or not, since ancient times.

Lactose intolerance is a natural thing to study. The ability to manufacture the lactase enzyme as an adult is a simple mutation that is easy to spot. I posted another item about a different study in December, Milk Mutation "Strongest Signal of Selection", in which I quoted University of Maryland biologist Sarah Tishkoff as saying that the LI mutation arose so quickly and was so advantageous that "it is basically the strongest signal of selection ever observed in any genome, in any study, in any population in the world."

In addition,

Tishkoff's team determined the date range when the mutation likely occurred: 3,000 to 7,000 years ago, which matches up well with the archaeological record that places pastoralization coming to East Africa about 5,000 years ago. The European trait dates back about 9,000 years.

The new study does little more than move that European date closer to the present.

An article, Early Europeans unable to stomach milk by Roxanne Khamsi at NewScientist.com reports that:

Researchers analysing the DNA in Neolithic human remains claim to have uncovered the first direct evidence that modern humans have evolved changes in response to natural selection.

Just 7000 years ago, Europeans were unable to digest milk, according to a new analysis of fossilised bone samples – nowadays more than 90% of this population can.

Well, cool. This is extraordinarily difficult and exacting work and is a major advance in the techniques of gene identification.

But a major finding? Perhaps not.

To determine when this special lactose tolerance evolved in Europe, Thomas’s team analysed the DNA from 55 bone samples belonging to eight Neolithic Europeans. The skeletons were dated to between 5840 BC and 5000 BC.

Eight people. I rail at medical journal articles when the study group is that small, because findings are simply all too likely to show up by sheer chance in small groups. Would you be surprised to find no left-handers in a group of eight people?

It's not quite that simple, of course. The number of ancient bones that usable DNA can be extracted from is limited. We'll learn more about the statistical significance of the study when it is published.

Nobody whose read my book or the earlier, admittedly non-genetic, research on LI should be in the least surprised by these findings, however. While interesting, this news is not exactly news.

If there's more to it than first appears, I'll revisit the subject and fill you all in.