Altruism, the act of helping others at personal cost, has deep evolutionary roots. This behaviour can be seen across many species, from humans to insects. One theory suggests that altruism evolved because it increased the survival chances of close relatives, thus helping to pass on shared genes. This is known as kin selection.
Another theory, reciprocal altruism, posits that individuals act altruistically because they expect the favour to be returned in the future. This theory is supported by evidence from vampire bats, which share blood meals with others, even when they are not related, expecting the favour to be returned later.
However, these theories do not fully explain why humans help strangers without expecting anything in return. This type of altruism, known as strong reciprocity, is unique to humans and is thought to have evolved due to the complex social structures of human societies. In these societies, individuals who behave altruistically are more likely to be trusted and cooperated with, thus increasing their chances of survival.
Altruism is not purely instinctive but is influenced by cultural and social norms. For instance, societies with a strong sense of fairness and equality tend to have higher levels of altruism. Altruism can also be learned and can change over time. This flexibility allows altruism to adapt to changing social environments, ensuring its continued survival in the evolutionary process.
Go to source article: http://www.prospect.org/article/evolutionary-roots-altruism