From an evolutionary perspective, human pregnancy is quite strange, says University at Buffalo biologist Vincent Lynch.
“For example, we don’t know why human women go into labor,” Lynch says. “Human pregnancy tends to last longer than pregnancy in other mammals if you adjust for factors like body size. The actual process of labor tends to last longer than in other animals. And human pregnancy and labor are also much more dangerous.”
With these oddities in mind, Lynch and colleague Mirna Marinic set out to investigate the evolution of a gene that helps women stay pregnant: the progesterone receptor gene.
But the results of the study only add to the mystery, says Lynch, PhD, an assistant professor of biological sciences in the UB College of Arts and Sciences.
Their research finds that while the progesterone receptor gene evolved rapidly in humans, there’s no evidence to support the idea that this happened because those changes were advantageous. In fact, the evolutionary force of selection was so weak that the gene accumulated many harmful mutations as it evolved in humans, Lynch says.
“Pregnancy is such an everyday event — none of us would be here without it — and yet, so many aspects of this process remain puzzling,” says Marinic.