The model of modern human origins depends, in part, on the archaic interbreeding of Neanderthals and Homo Sapiens (not the modern Homo Sapiens Sapiens, which is what human beings are to this day.) From this coupling rose a species, us, which was tough and less impervious to cold, a quality gained from the Neanderthals, and a more robust brain size, a quality obtained from Homo Sapiens.