Sunday, August 28, 2016

An Ä+ for Svante ‎Pääbo's Neanderthal Man: In Search of Lost Genomes

by Drew Martin
The hand axes and eagle talon necklace pictured here were fashioned by Neanderthals more than 100,000 years ago; tens of thousands of years before modern humans arrived in Europe. In fact, these Neanderthal inventions predate modern human tooling and crafting.

While Neanderthals may not have produced sculptures and paintings, they were apparently fond of collecting knick-knacks and certainly had an eye and appreciation for symmetry and adorning themselves.

I just finished reading Neanderthal Man: In Search of Lost Genomes, which is Svante Pääbo's fascinating explanation of how he and his team first sequenced the genome of Neanderthals and then Denisovans (another early hominin, which Pääbo first discovered through gene sequencing). 

Pääbo is diligent in explaining all the trials and tribulations of his quest, which include managing bacterial and human contamination of their samples and perfecting the clean room, getting enough prehistoric hominin bone to sample, finding the most efficient and accurate sequencing machines, worrying about the competition who might publish their findings ahead of Pääbo's group, and handling the critics, which range from creationists to other scientists less enthusiastic about genomic analysis.

A good understanding of biology is helpful to fully grasp Pääbo's more scientific writings about DNA, but even without that I think one would still be impressed by the process he describes. 

While this is not a travel book, Pääbo does take you a bit around the world including his research in Berkeley, California, setting up his department in Leipzig, Germany with the Max Planck Institute, a romantic awakening in Hawaii, and several bone-sourcing trips to Croatia and Russia, where he learns a lot about friendship.

What comes of all of this is a clearer understanding of our relationship to Neanderthals and the dispelling of less probable scenarios. It is now understood that we are much closer to Neanderthals than we previously comprehended. We shared an ancestor in Africa, but the group that evolved into Neanderthal left to Europe about 800,000 years ago. There appears to be a couple waves of modern humans that later joined them. The first wave lived among them and had fertile offspring. A subsequent wave of humans mixed with the interbred humans and spread out into the rest of the world with new technologies and a greater gift of exploration.

One thing 
Pääbo tries to make clear several times, is that whichever the correct order of events, Neanderthal aren't exactly extinct as previously explained when it was thought that humans were a replacement group that did not mate with them. The fact that humans and Neanderthals had children together means that everyone who is not purely African has a certain percentage of Neanderthal genetic information in them. An interesting topic that is teased out of their studies is gene flow. It is clear that in the first interchange of genes, male Neanderthals were impregnating female humans, which would contradict the thought of human dominance over the Neanderthals.

Pääbo is an interesting writer, devoted to his topic, but also willing to make numerous asides:

I was intrigued, but again. I was also worried. There might be a stigma associated with being "Neanderthal." Would people feel bad if they knew that some part of their genome that carried genes involved in how brain cells work came from Neanderthals? Would future arguments between spouses include arguments such as "You never take out the trash because such-and-such brain gene of yours is Neanderthal"?  

And when discussing testicle size in relationship to promiscuity, Pääbo offers:

Humans, as measured both by testicle size and evidence for positive selection on genes relevant for male reproduction, seem to be somewhere between the extremes of chimpanzee promiscuity and gorilla monogamy, suggesting that our ancestors may have been not so unlike us, vacillating between emotionally rewarding fidelity to a partner and sexually alluring alternatives.