Evolution: Why Chimp Faces Evolved Differently from Human Faces
A chimp's face is different from that of a human. Now, though, researchers have taken a closer look at evolution and have found how these structural differences could arise in two species with nearly identical genetic backgrounds.
"We are trying to understand the regulatory changes in our DNA that occurred during recent evolution and make us different from the great apes," said Joanna Wysocka, one of the researches, in a news release. "In particular, we are interested in craniofacial structures, which have undergone a number of adaptations in head shape, eye placement and facial structure that allow us to house larger brains, wlak upright and even use our larynx for complex speech."
It turns out that the key lies in how genes involved in facial development and human facial diversity are regulated. In this latest study, the researchers used a process called cellular anthropology, which is mimicking some steps of early primate development in a dish. This allowed them to study gene expression.
The researchers first had to obtain a specialized type of cell present only in very early primate development. The cells, called cranial neural crest cells, originate in humans within about five to six weeks after conception. Although they first appear along what eventually becomes the spinal cord, the neural crest cells then migrate to affect facial morphology and differentiate into bone, cartilage and connective tissue.
"Of course, humans and chimps are very closely related," said Wysocka. "Most of the regulatory elements are the same between the two species. But we did find some differences. In particular, we found about 1,000 enhancer regions that are what we termed species-biased, meaning they are more active in one species or the other. Interestingly, many of the genes with species-based enhancers and expression have been previously shown to be important in craniofacial development or associated with normal intrahumman facial variation."
The findings are published in the journal Cell.
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