Researchers at Israel’s Weizmann Institute investigating the protein tyrosine hydroxylase (TH) found in the brains of humans and animals, have discovered that low TH levels increase aggression in males. High TH levels reduce aggression in males but increase motherly instincts in females.
http://www.timesofisrael.com/how-to-tame-a-male-weizmann-researchers-may-have-the-answer/