One possible explanation for this phenomenon is simple supply and demand. (educationnext.org)
It may be that researchers were trying to find simple explanations for phenomena that, in nature, have lots of different functions in different animal groups. (sciencemag.org)
Nobody has a full explanation for this phenomenon, and we are left in that very familiar mystical state: the one where we still don't have all the answers. (discovermagazine.com)