According to a recent article in Slate, researchers believe the evolution of human pregnancy may be linked to a parasitic DNA (10-07) that infected our ancestors by replicating itself throughout their genomes 100 million years ago (10+08).
Scientists studied the uterine cells of three contemporary mammals, specifically opossums, armadillos and humans. Their goal was “… to explain how our ancestors developed a more advanced kind of gestation—including the ability to carry fetuses in the womb until they reached a more developed state.”
“Using a sequencing approach that allowed for large-scale analysis, they considered the genes that were turned on in each of these animals during pregnancy. Then they homed in on differences between the marsupial opossum and the placental mammals, the armadillo and the human. Remarkably, they found that new stretches of DNA, called transposons, were scattered throughout the armadillo and human cells. These transposons appeared to act as light switches for genes that got turned on only in the uteruses of the more advanced animals.”