Question

Why would most evolutionary biologists expect kin selection to be the main (or only) mechanism by which altruism occurs?

Why have evolutionary biologists struggled to explain the adaptive significance of altruistic behavior?

Answer 1

Altruism means the behavior that benefits another individual at a cost to oneself. Let's say, for example, giving your lunch away is altruistic because it helps someone who is hungry, but at a cost of being hungry yourself. The animals and humans are more altruistic towards close kin than to distant kin and non-kin. This mechanism by which altruism works has been confirmed in various studies across many different cultures. There are many cues for indicating kinship. One is facial resemblance. Another cue is having the same family name. These have been found to increase altruistic behavior. In humans, altruism is on a large scale with kin than unrelated individuals. In other species like velvet monkeys, they use allomothering, where related females such as older sisters or grandmothers often care for young, according to their relatedness. We give presents according to how close we are to the recipient. So, most biologists expect kin selection to be the main mechanism by which altruism occurs.

Kin selection is an example of adaptive behavior that directly influences the genetic composition of a population. It involvs evolutionary strategies that favor the persistence of an organism's relatives, often at a cost of the organism's own survival and reproduction. But, this may not be the case always. Sometimes, the individual would be more concerned for his survival and reproduction. So, that individual might not behave in an altruistic way towards his kins. By doing that, many changes takes place for the survival of the fittest. These are called variations. This contributes to evolution. Newly evolved species are formed by this. But if they always behave altruistically, the same genes will be passed on to the next generation. That is why the biologists struggled to explain the adaptive significance of altruistic behavior.