Many of the evolutionary adaptations which we enjoy, as mammals, are often closely aligned with the common wisdom on virtuous behavior. Even from a scientific rationalist perspective, there is such a thing as "kindness:" an instinctive range of highly constructive maternal and paternal nurturing patterns that are built into our very DNA. Most reptiles lack this altogether, due to the lack of the neocortex, a sheath around the reptile brain which developed in mammals hundreds of thousands of years ago.
Most lizards are basically survivalistic bastards, though some are just really lazy. In stark contrast are human beings, who are at the top of the mammalian cognitive complexity range.* The problem with human awareness, which has caused so many global problems in turn, is that we all still have a reptile brain, lurking beneath the neocortex like a Social Darwinism-spouting tumor. Our logical centers have a kind of genetic romance with this ugly character, since they dated before the Neocortex came along and swept Reason off its feet. But for most people, reason is mostly dating the neocortex, a bit of cheating notwithstanding. It loves love; love illuminates out rational processes like nothing else. Hell, even the ego can get into it, because keener reason allows for more survivability, and the ego is basically an agglomeration of primal instinct and reason (another reptilian throwback).
PS: yes, Mr. Alligator is so ornery because of the medula oblongata.
*Except possibly for cetaceans, who have the good sense to swim around having recreational sex all the time yet maintain a sustainable level of population (think about it for a second.. wait for it.. wait for it... makes sense, right?) In any event, one could argue that humans have the most opportunities to combine those mammalian warm fuzzies with hard logic in novel ways.
