How Altruism Might Have Evolved
I spend a lot of time in my book Liars and Outliers on cooperating versus defecting. Cooperating is good for the group at the expense of the individual. Defecting is good for the individual at the expense of the group. Given that evolution concerns individuals, there has been a lot of controversy over how altruism might have evolved.
Here’s one possible answer: it’s favored by chance:
The key insight is that the total size of population that can be supported depends on the proportion of cooperators: more cooperation means more food for all and a larger population. If, due to chance, there is a random increase in the number of cheats then there is not enough food to go around and total population size will decrease. Conversely, a random decrease in the number of cheats will allow the population to grow to a larger size, disproportionally benefitting the cooperators. In this way, the cooperators are favoured by chance, and are more likely to win in the long term.
Dr George Constable, soon to join the University of Bath from Princeton, uses the analogy of flipping a coin, where heads wins £20 but tails loses £10:
“Although the odds [of] winning or losing are the same, winning is more good than losing is bad. Random fluctuations in cheat numbers are exploited by the cooperators, who benefit more than they lose out.”
EDITED TO ADD (8/12): Journal article.