One thing that seems to baffle religious people no end is why non-religious people behave decently when they aren't expecting a reward or fearing punishment. What they can't seem to grasp is why people bother to cooperate and aren't simply selfish. Strangely though, they take umbrage at the suggestion that, if this applies to them, they are admitting to being a sociopath with no feelings for their fellow man nor any ability to empathise with others.
If you're religious you're probably thinking that's not fair. You do right because it's the right thing to do. It's just that you can't trust all the others, so you want them to be motivated by reward and punishment because that makes them more reliable; more controlled and predictable. You don't need that, obviously, because you can be trusted to do the right thing! In fact, what you believe in is belief itself. For more on this see Believing in Belief.
A study, published in Current Biology and reported on by Guy Riddihough in Science shows that cooperative behaviour probably evolved because it leads to greater long-term success, especially in an expanding population which, for most of its recent history was what Homo sapiens was and which many populations continued to be until very recently.
The team genetically engineered yeast to form two populations to act as cooperators and defectors respectively. Both populations were unable to absorb the disaccharide sugar sucrose from their growth medium but both could absorb the simpler monosaccharide sugars (glucose and fructose) into which sucrose can be broken down with the enzyme invertase.
The cooperators could produce and excrete invertase making glucose and fructose available for all populations but the defectors had been mutated to prevent invertase production. Since there was a cost to the cooperators in producing invertase but not to the free-riding defectors, defectors would be expected to be the main beneficiaries of this system.
This system is analogous to the Game Theory Prisoner's Dilemma:
What the researchers found was:Two members of a criminal gang are arrested and imprisoned. Each prisoner is in solitary confinement with no means of speaking to or exchanging messages with the other. The police admit they don't have enough evidence to convict the pair on the principal charge. They plan to sentence both to a year in prison on a lesser charge. Simultaneously, the police offer each prisoner a Faustian bargain. If he testifies against his partner, he will go free while the partner will get three years in prison on the main charge. Oh, yes, there is a catch ... If both prisoners testify against each other, both will be sentenced to two years in jail.In this classic version of the game, collaboration is dominated by betrayal; if the other prisoner chooses to stay silent, then betraying them gives a better reward (no sentence instead of one year), and if the other prisoner chooses to betray then betraying them also gives a better reward (two years instead of three). Because betrayal always rewards more than cooperation, all purely rational self-interested prisoners would betray the other, and so the only possible outcome for two purely rational prisoners is for them both to betray each other. The interesting part of this result is that pursuing individual reward logically leads the prisoners to both betray, but they would get a better reward if they both cooperated. In reality, humans display a systematic bias towards cooperative behavior in this and similar games, much more so than predicted by simple models of "rational" self-interested action.
...as the colonies grow, the cooperator populations expand at the expense of the defectors. The cooperators form genetically demixed sectors, analogous to "genetic surfing" seen in frontier populations. Simulations support the idea that an expanding colony frontier favors (cooperative) genotypes that maximize group productivity and that this could apply to range expansions seen in many species, including humans.So we see that an expanding population is likely to be more successful and so continue to expand if its members cooperate. Cooperation is thus a consequence of expansion and genes for cooperation benefit from the situation in which they find themselves. As always with evolution, it's not just the genetic change which matters but the context of the environment in which that change occurs which facilitates evolution.
Cooperative Yeast Break Free; Guy Riddihough;
Science 7 June 2013: Vol. 340 no. 6137 p. 1143 DOI: 10.1126/science.340.6137.1143-b
Human evolution is a little more complex than yeast evolution, not because the basic principles are different but because we have an additional set of replicators - our memes. Memes are units of cultural inheritance and are no less inherited replicators than our genes. This is where our morality resides. Morality is simply the set of inherited rules by which we ensure cooperation by regulating our interpersonal interactions. What our genes allow us to do is to empathise with other people - to put ourselves in their place and see things through their eyes. This way we know what they would have us do unto them. We don't always do it that well and some are better at it than others, but all humans have the innate ability to cooperate and the learned ability to select the right rules for task.
And of course, the rules vary from place to place and from people to people because they evolved in different frontier populations at different times and in different situations. This difference is how we know they evolved and weren't handed down to us by some divine authority thought up by Bronze-Age goat-herders who knew no better.
Cooperative Yeast Break Free; Guy Riddihough; Science 7 June 2013: Vol. 340 no. 6137 p. 1143; DOI:10.1126/science.340.6137.1143-b'via Blog this'
Van Dyken et al. Curr. Biol. 23, 919 (2013)
Religion: An Abdication of Moral Responsibility.