Also need to hear adult males when they are older and beginning to practice their song. But in some cases the interaction of genetics and environmental factors can cause the differences can disappear. Genes and Behavior Many genes probably influence the development and performance of most behaviors, but it only takes one abnormal gene to screw it up. There is a much lower incidence among blacks. Causes a build up of phenylalanine if normal diet is consumed.
Some genes affect behavior by even more indirect routes.