Adaptive Introgression of Neanderthal Genes

Samara Tawziat Choudhury
Graduated student (now a Master's student at North Dakota State University)
School of Life Sciences
Independent University, Bangladesh

March 23rd, 2019

You might think that this (pictured) is a human skull, but is, in fact, a replica of a Neanderthal skull.

Image from Dinosaur Corporation

Neanderthals were a human-like species-- not humans, mind you, that went extinct about 24,000 years ago. So did we get to meet them?

Well, I’m going to tell you a story. More than a hundred thousand years ago in Africa, where all humans were born, a particularly daring group decided it was time to venture out into the world.

More humans followed them and before you knew it, we were everywhere, all over the world.  On one of these expeditions around 70,000 years ago, we met the Neanderthals. In fact, not only did we meet them, we fell in love with them.

Neanderthals and humans coexisted and mated and consequently, exchanged genes. Genes are the biological material that we inherit from our both of our parents that make each of us who we are. Our genes will determine whether we have black eyes or blue, are short or tall, have dimples or not, and importantly, whether we are more likely to get a certain disease or not.  

Humans have their own set of genes, and Neanderthals have their own. Neanderthals have gone extinct since we met, but the genes that they gave us are still in our genome, which is referred to as an introgression. Why?

Recently, a study looked at one such set of genes, and showed that it is very impropable that they should remain in us for so many years.  But, they have. As with everything else, if we hang on to something, then it’s probably something important.  So why are Neanderthal genes important for us to keep in our bodies even after all these thousands of years?

It turns out that some of these genes are involved in keeping us safe from viruses that cause disease. The study showed that the Neanderthal version of some immune genes found in Europeans and Asians differ in function from the human version.  So, as we moved from one place to another, we may have kept the Neanderthal genes within us to keep us safe from diseases we were likely to encounter in new and unknown places. Thus, these introgressions had an adaptive benefit.

Ladies and gentlemen, I would like to leave you all with a simple thought: that somewhere in us is a small part of a long-forgotten species, the Neanderthals.  And that they have probably protected us more times than we can count. Now that is truly amazing. Thank you.

Source to explore:
Original study
Report on the original study
More recent work

Samara dreams of curing diseases and working for the WHO. She also loves to cook, and has a weird wish to be buried in a library so that her soul can read books for eternity.