Humans may be responsible for a jump in brain growth among mice and some other small mammals living around us in both urban and rural settings, a new study finds.

Small mammals that either produce a lot of babies or eat a lot of bugs exhibited the greatest cranial capacity (i.e. brain growth) due to human-caused environmental changes over the past century, suggests the study, which is published in the latest Proceedings of the Royal Society B.

“Small mammals with high fecundity (such as deer mice and meadow voles) show the most pronounced differences in cranial capacity between urban and rural environments, having larger cranial capacity in urban environments,” lead author Emilie Snell-Rood told Discovery News.

Are We Causing Animals to Grow Bigger Brains? : Discovery News.