Genetically mixed populations can help understand human diversity, origins: Expert

February 15th, 2009 - 3:05 pm ICT by ANI  

Washington, February 15 (ANI): A Penn State physical anthropologist says that genetic diseases and genetically mixed populations can prove useful in understanding human diversity and human origins.
“We wanted to get to a strategy to predict what a face will look like. We want to understand the path of evolution that leads to that part of the selection process,” said Mark D. Shriver, associate professor of biological anthropology.
He revealed that with an eye on pinpointing genes that influence the shape of the human face and head, he began with an online database of genes linked to disease — Online Mendelian Inheritance of Man.
If the symptoms of the disease involved the face or skull the gene implicated in the disease became a candidate for those facial traits, said the researcher.
Shriver says that the his approach works because, though he looked at genes implicated in disease, those same genes in a healthy person may also influence the same physical trait — length, width, shape, size — but within the range normal for healthy individuals.
The researcher highlights that fact that facial traits vary among humans, but do tend to group by population.
In general, according to him, West Africans have wider faces than Europeans and Europeans have longer faces than West Africans.
“There is a strong relationship between genetic ancestry and facial traits. Using individuals of combined ancestry, European and African, we can see how the target genes alter facial traits,” he told attendees at the 2009 Annual Meeting of the American Association for the Advancement of Science.
The study was concentrated on a combined sample of African Americans with West African and European ancestry, whose genetic makeup was known through DNA testing.
The researchers made it simpler by eliminating anyone with Native American ancestry, so that only two genetic pools were represented — West African and European.
They reported on a sample of 254 individuals using three-dimensional imaging, and measured the distances between specific portions of the face.
Each individual had provided a DNA sample.
“We started with 22 landmarks on the faces that could be accurately located in all the images,” said Shriver, adding that these landmarks might be the tip of the nose, the tip of the chin, the outer corner of the eye or other repeatable locations.
The research team then recorded the distances between all the points in all directions, in order to have a distance map of each of the faces.
From their DNA profiles, Shriver could determine the admixture percentages of each individual, how much of their genetic make up came from each group.
He could then compare the genetically determined admixture to the facial feature differences and determine the relative differences from the parental populations.
“This type of study, done on admixed populations shows that each person is a composite of their ancestors and that the range of facial features is a continuum,” says Shriver.
He and his colleagues observed that there was a very strong statistical correlation between the amounts of admixture and the facial traits.
“We chose to look at African Americans because they were a large enough and available admixed population. We are trying to solidify our understanding of the origins of humans and the evolutionary processes. Looking at admixed populations shows us the influence genes have and how they relate to physical features,” said Shriver. (ANI)

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