A study recently published in the Proceedings of the National Academy of Sciences has found that while most people of Asian decent are lactose intolerant, some East Asians are not, and they likely have Neanderthals’ to thank for it. All modern humans have some Neanderthal DNA in them, which can have a variety of impacts on our genetic makeup.

Lactase persistence (aka, lactose tolerance) was once thought to have evolved in humans sometime between 5000 and 10,000 years ago, when our ancestors first started raising cattle and using their milk in our diets.

According to this new study, however, it seems that the genes needed for lactase persistence were actually formed thousands of years before this by human ancestors. Of course, since the people with these genes didn’t originally drink milk beyond infancy, the genes likely developed for other purposes.

The researchers looked at the genomes of thousands of people from around the world, with specific interest in the LCT gene. In this research, a suite of associated genes called a haplotype that was previously unknown was found in about 25% of East Asians. This is a different haplotype than what is thought to make it so most Europeans can tolerate lactose.

It appears that this haplotype originated in Neanderthals some 25,000-28,000 years ago.

The authors of the study say:

“Given the origin of this haplotype from Neanderthals and the old age for the onset of selection, it is highly unlikely that the reason for positive selection involves LP.”

One interesting thing that the researchers noticed is that both the haplotype in East Asians and the one in Europeans alters a gene known as DARS1. This gene is important for immune cells.

So, it is likely that both of these haplotypes evolved over time as a way to improve the immune systems of the Neanderthals, and gaining the ability to tolerate lactose was just a happy side effect.

As someone who enjoys dairy very much, I am just glad that this took place.

Evolution is amazing.

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