“The researchers analyzed MRI scans of 218 humans and 206 chimpanzees, with an eye on brain size and organization—the latter of which they assessed by noting for each brain the location of 16 landmark anatomical structures that humans and chimps share. Because the researchers knew the respective biological relationships of both the chimps and the humans in the study, they were able to estimate the heritability—in other words, how much of a role genetics had to play—for both traits.”