The out of Africa theory has gotten another line of evidence under its belt, this time from a genetic comparison of the bacteria that we all have in our digestive system. This bacteria is called Helicobacter pylori and depending on which subpopulation of human you are, you have a distinctive strain in your guts. Genetic drift is the mode that creates distinctive strains, because as populations split off from one another genetic mutations become more prevalent. Sampling bacteria, in this case, is more definitive because bacteria have an exponentially faster generation cycle than humans, meaning mutations are even more bold and have a higher resolution throughout evolutionary time.
Each of these strains can tell us where our ancestors came from if we just retrace the ‘path of pebbles’ along the way. That’s exactly what some researchers over at Max Planck’s intellectual powerhouse, and other institutions, have studied. Their findings were just published in Nature, under the title, “An African origin for the intimate association between humans and Helicobacter pylori.”
Basically, the researchers had to first order populations of humans and bacteria and to do so they employed the principle of isolation by distance. This meant that they had to sample H. pylor genes from populations who hypothetically split off from the main pack the most and compare them to the one another. Which in turn, if the data matches and it does, is the foundation of the Out of Africa theory.
In ScienceDaily’s words, this principle relies on the general consensus that,
“the genetic distance between two populations has a linear correlation with the length of the migration paths taken since they were separated. “It’s actually quite logical,” explains Dr. Mark Achtman, “because in the time that elapses after a population leaves its point of origin, the number of mutations in its genetic makeup continually increases.”However, while man was spreading throughout the world, human populations had to repeatedly pass through what scientists call genetic bottlenecks: when a population shrinks, the gene pool also becomes smaller. These losses in genetic diversity linger, even when the population starts once again to increase in number. Since the Homo sapiens populations usually had to pass through several genetic bottlenecks on their way across the globe, their genetic diversity declined the further they journeyed from their origin in East Africa.
Scientists have now uncovered similar signs of historical population migration in the genetic makeup of H. pylori.”
I must give props to the researchers for applying their studies in this manner. It is truly creative to focus on a bacteria, which as I said, has a more definitive mutation rate, and apply that to do some migration pattern analysis is impressive. I maybe jumping the gun but, I feel that this bacterium has given us more information on aspects of human history than the fossil record has given us to date.