NEWS - 'Homo' is the only primate whose tooth size decreases as its brain size increases

Andalusian researchers, led by the University of Granada, have discovered a curious characteristic of the members of the human lineage, classed as the genus Homo: they are the only primates where, throughout their 2.5-million year history, the size of their teeth has decreased alongside the increase in their brain size ...

http://phys.org/news/2014-04-homo-primate-tooth-size-decreases.htm