Toxoplasma, that mind-altering, cell-manipulating, all-around awesome parasite that sits in the brains of billions of us, is back in the news. Infection with the parasite raises the chances a woman will have a boy from 51% to 72%. The average ratio of boys to girls at birth is 51%. Women with high levels of antibodies to Toxoplasma, scientists found, have a 72% chance of having a boy. While many effects of Toxoplasma probably have something to do with adaptations that allow the parasite to thrive and spread successfully, this one seems more like a side-effect, albeit a dramatic one.
Paper abstract here.
[Thanks to BC for the fact-check.]
Originally published October 12, 2006. Copyright 2006 Carl Zimmer.