The headline making some buzz today, “Gene regulation, not just genes, is what sets humans apart,” isn’t the most Earth shattering of a statement the press is making it out to be. Most biologists and physical anthropologists have been holding, for a long time, the opinion that gene regulation is the key reason as to why humans differentiated from our other primate relatives. So the impact of gene regulation in human evolution, is actually pretty common knowledge… it even came up in a discussion on our other blog, Primatology.net way back in March of this year.
Even though we held these thoughts, the findings behind the headline are still important. Just published in Nature Genetics, the findings confirm what we’ve been thinking of all along. The paper, “Promoter regions of many neural- and nutrition-related genes have experienced positive selection during human evolution,” comes from Ralph Haygood, a post-doctoral fellow in Gregory Wray’s laboratory over at Duke University’s Biology department.
“His group looked at the regulatory sequences immediately adjacent to 6,280 genes on the DNA of chimps, humans and the rhesus macaque, a more distant primate relative that has 88 percent the same genes as humans. These regulatory stretches of DNA are where proteins bind to the genome to initiate a gene’s function. And it is here that evolution has apparently fine-tuned the performance of genes, Wray said, resulting in the dramatic differences in the human brain.
Though many studies have looked for significant differences in the coding regions of genes relating to neural system development and failed to find any, the Duke team believes this is the first study to take a genome-wide look at the evolution of regulatory sequences in different organisms.
Other studies have found significant differences between these species in the coding regions… as far back as 1975 when Mary-Claire King and Allan Wilson first said humans and chimps were 99 percent the same genetically, they had offered the suggestion that greater differences might be found in the regulatory regions.
The type of analysis performed by the Duke team couldn’t be done until the macaque genome was published in 2005 because they needed a third, closely related relative to compare the regulatory sequences…
To do a genome-wide analysis of regulatory regions, Haygood and post-doctoral fellow Olivier Fedrigo had to adapt some of the statistical tools used for genome-wide analysis of coding regions. To be sure their results would be robust, they focused on just the most reliably accurate published DNA sequences in common between the three animals, discarding two-thirds of the genome to ensure accuracy. “With only three species, we had to be very stringent about quality,” Fedrigo said.
The researchers don’t think these findings will be of any help resolving questions about how and when the ancestors of humans and chimps diverged on the tree of life…”
With more and more primate genomes being sequenced, experiments like this comparative genomic study, give us evolutionary insights that we couldn’t make from analyzing fossils, behaviors, and artifacts alone. Sometimes these experiments help identify novel genes, and sometimes they confirm what we’ve been thinking all along. In this case, it was the later. Since most primates share at least 90% of the same genetic sequences, it is in the ways genes are activated, regulated, the patterns of their expression and ultimately how and when they play out throughout development, that drive forward most differences we see in primates.