"The subtle but ongoing pressures of human evolution could explain the seeming rise of disorders such as autism, autoimmune diseases, and reproductive cancers, researchers write in the Proceedings of the National Academy of Sciences. Certain adaptations that once benefited humans may now be helping such ailments persist in spite of -- or perhaps because of -- advancements in modern culture and medicine...
"Autism and schizophrenia may be associated with the over-expression of paternally or maternally derived genes and influences, a hypothesis advanced by Bernard Crespi of Simon Fraser University.
"Maternal and paternal genes engage in a subtle tug-of-war well into childhood with consequences for childhood development, as posited by David Haig, George Putnam Professor of Organismic and Evolutionary Biology at Harvard.
"Humans may be susceptible to allergies, asthma, and autoimmune diseases because of increased hygiene, according to Kathleen Barnes of Johns Hopkins University. Without being exposed to intestinal worms and parasites, as our ancestors were, our immune systems are hypersensitive.
"Natural selection still influences our biology, despite advances in modern culture and medicine. Stearns found that natural selection favors heavier women and reduces the age at which a woman has her first child."