62:3.3

Their brains were inferior to, and smaller than, those of human beings but very superior to, and comparatively much larger than, those of their ancestors. The twins early displayed superior intelligence and were soon recognized as the heads of the whole tribe of dawn mammals, really instituting a primitive form of social organization and a crude economic division of labor. This brother and sister mated and soon enjoyed the society of twenty-one children much like themselves, all more than four feet tall and in every way superior to the ancestral species. This new group formed the nucleus of the mid-mammals.