"The easiest way for us to do this is to look at situations where there's been very strong selective pressure: a disease with a really high mortality rate, or here at high-altitude where there are hypoxic conditions. This kind of situation makes a dramatic difference in terms of who passes on their genes, so it gives us more power to find the genetic signatures left behind."
Pregnant women are especially susceptible to the physiological pressure represented by hypoxia, which influences the birth weight and health of their children. Yet people have been living in the high-altitude regions of the Andes and the Tibetan Plateau for generations, with little apparent ill effect.
Anthropologists, notably, Cynthia Beall, of Case Western University, and Lorna Moore, of Wake Forest University, have therefore extensively documented their physiological traits, trying to understand how these groups offset the problems pregnant women would normally have in hypoxic environments. More recently, geneticists have attempted to correlate these physical traits, or phenotypes, with the genes that are responsible for them, or genotypes.
Researchers have long wanted to add additional populations for comparison, and while the people of the Ethiopian Highlands met the criteria, living at over 3,000 meters above sea level, economic, linguistic and geographic hurdles stood in the way of collecting the data.
"This was an extremely challenging study. The logistics alone, getting permits and permission to do this trip, took us many years," Tishkoff said.
"Sampling from these remote populations was also very difficult," said Simon Thompson, who was part of the group's field team. "Roads were impass
|Contact: Evan Lerner|
University of Pennsylvania