Eve: How the Female Body Drove 200 Million Years of Human Evolution

by Cat Bohannon

While a lot of attention is given to the fact that women’s bodies tend to be smaller, the reason we metabolize drugs differently may actually have as much to do with our livers. One recent study comparing biopsies of male and female liver tissue showed thirteen hundred genes whose mRNA expression was significantly influenced by sex; of these, 75 percent showed higher expression in females (Renaud et al., 2011). It’s not, in other words, just a matter of how much drug distributes through how much body mass, but how the cells in a sex-typical liver go about their day. And “day” matters here, too: livers, like the rest of the body, have a circadian rhythm, and female mammals are especially sensitive to our long-evolved relationship to the sun (Lu et al., 2013). More on daylight and why it matters in the “Perception” chapter.