Jaroslav Flegr

Jaroslav Flegr (born 12 March 1958) is a Czech parasitologist, evolutionary biologist, and author of the book Frozen Evolution. He is professor of biology at the Faculty of Science, Charles University in Prague, and is a member of the editorial board of the journal Neuroendocrinology Letters.

His work on how toxoplasmosis—an infection caused by the protozoan parasite T. gondii—influences personality, sex ratios, and rates of traffic accidents, has received coverage in The Atlantic, Salon, and The Guardian. Flegr maintains that toxoplasmosis might increase the rate of traffic accidents by as much as one million collisions per year. He also believes that T. gondii contributes to suicides and mental disorders such as schizophrenia. His hypothesis of frozen plasticity is an extension of Niles Eldredge and Stephen Jay Gould's theory of punctuated equilibria, which describes the history of most fossil species as being relatively stable for millions of years, later punctuated by swift periods of evolutionary change during speciation.