Top Story: August 27, 2012

Hunter-Gatherer Genes

Baka_dancers_June_2006

Several weeks ago, the journal Cell published a gene study of three hunter-gatherer populations in Africa.

The authors of the paper sequenced the entire genomes of five members of each of the following hunter-gatherer populations: forest-dwelling, short-statured Pygmies from Cameroon, and click-speaking Hadza and Sandawe individuals from Tanzania.

The fascinating findings tell us more about human origins and prove to be a bit controversial, so I wanted to get more information from the Academy’s expert in human evolution, Zeray Alemseged. Zeray’s studies of early human remains have been published in prominent journals and garnered him worldwide attention. (PBS’s NOVA filmed an extensive interview with him here last spring, in addition to being on the covers of Nature and National Geographic.)

Zeray says these populations are not well studied and their isolation offers a new view on the human genome. Their unique diets, stature and culture also enable scientists to potentially link specific attributes to genetic markers, he adds.

 

The researchers used an in-depth method that involves sequencing each strand of DNA more than 60 times on average. This redundancy makes the sequencing highly accurate, giving the geneticists confidence that any mutations they identify are real and not errors.

Their results suggest that different human populations evolved distinctly in order to reap nutrition from local foods and defend against infectious disease. They also identify new candidate genes that likely play a major role in making Pygmies short in stature.

Scanning these sequences, the researchers found 13.4 million genetic variants or mutations—locations in the genome where a single nucleotide differed from other human sequences—and astonishingly, 3 million are new to science.

These new variants can represent the gene expressions unique to these populations, Zeray explains. This study is quite significant in making these genetic links to function and attributes that are phenotypic.

Zeray reminds us that these genetic studies aren’t just for mapping our ancestry, but also for mapping our future. He offers two separate examples—first, personalized medicine could tailor to specific gene regions. Second, “If we can link variants to diet, isolation and environment,” Zeray says, citing this current study’s examples, “then we can also understand what future climate change might look like for our species and how to prepare for it.”

Finally, the study finds genetic evidence that these direct ancestors of modern humans may have interbred with members of an unknown ancestral group of hominins. Zeray remarks that this particular finding—of a potential new species—reminds us why, in this technological age, paleoanthropology is a transdisciplinary endeavor requiring both fossil discovery AND genetic research.

So he’ll wait for more evidence, along with the rest of us…

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