There is substantial variance in the age at which children construct and deploy their first explicit theory of biology. This study tests the hypothesis that this variance is due, at least in part, to individual differences in their executive function (EF) abilities. A group of 79 boys and girls aged 5-7 years (with a mean age of 6½ years) were presented with two test batteries: (a) a biology battery that probed their understanding of life, death, and body functions and (b) an EF battery that tested working memory, inhibition, and set-shifting skills. Individuals' EF scores significantly predict their biology scores, even after controlling for age and verbal IQ.