The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [55]
All that has now changed. In the last 45 years or so, we have come to understand how natural selection gave us core morality. It turns out that doing so was integral and essential to the only adaptation that could have ensured our survival as a species. In fact, the adaptation that core morality constitutes enabled us to break out of that evolutionary bottleneck to which we were confined on the African savanna. We’ll trace that process here in a little detail because of its attractive consequences for the nihilism to which we are committed. It is crucial to remember, however, that in this story, all the links in the chain are forged by the laws of nature that Darwin discovered. It is these that make the explanation convey real understanding.
WHEN IT COMES TO HUMANS, NATURE HAD TO SELECT FOR NICENESS
Some components of core morality are easy explanatory targets for natural selection. Pretty much any norm that encourages good treatment of children and discourages bad doesn’t need a very complicated evolutionary explanation. It’s the components that encourage or require being nice to people genetically unrelated to you that has resisted evolutionary explanation. The most characteristic feature of human affairs is at the same time the one most recalcitrant to Darwinian explanation. The fact is, genetically unrelated people are nice to one another in many different ways, often without any guarantee or prospect of reward or reciprocation.
From the point of view of fitness maximization, this doesn’t seem to make any sense. Of course, in small family groups of very closely related members, being nice to others will be selected for because it favors one’s own (selfish) reproductive fitness; the people you are nice to will share your genes, and so their reproductive success will be yours, too. But once our hominin ancestors began to expand beyond the nuclear family, any tendency to niceness beyond the family should have been stamped out by natural selection, right?
This is not just a theoretical problem for human evolution. It was a concrete, life-or-death “design problem” faced by our hominin ancestors once they found themselves on the African savanna a few million years ago. They had been pushed out of the shrinking jungle rain forest by competition or because it was no longer capable of supporting them, or both. Our closet living relatives, the chimpanzees and gorillas, are still there, though hardly thriving themselves. It almost certainly was not intelligence or foresight that forced our ancestors onto the cooling, drying African plain. That’s the lesson of Lucy, the 3-million-year-old fossil hominin found in Ethiopia in 1974; she was bipedal, but her brain was no larger than that of other primates. Survival on the savanna started to select for upright walking, both to see threats and keep cool, long before it started to select for increased intelligence.
More than a million years ago, our ancestors were beginning to differ from the other primates in at least three respects: they were living longer; they were having more offspring, owing to a much reduced interval between births compared to other primates; and the offspring were dependent for longer and longer periods than other primate babies. These changes, of course, had been gradual, probably caused by a change in diet that had other consequences. On the savanna, there was meat to scavenge from the carcasses that the megafaunal top predators were bringing down. It was mainly to be found encased by bone, in marrow and brain that the top predators couldn’t get to. We could. Like chimps today, our ancestors were already using simple stone tools. Breaking bone was possible if they could only get to the carcasses quickly enough, then scare off the predator and keep it away. There wasn’t much chance of that—but there must have been a little.
Over time, the increased