Overlapping generations can promote altruistic behavior

Altruistic behaviors are “unselfish” behaviors—those that help another individual at the expense of the individual carrying out the behavior. Despite the negative consequences for the altruistic animal, these behaviors are thought to have evolved for several reasons.

Most altruistic behavior—in which one animal helps another at a cost to themselves—occurs between relatives. Scientists think these altruistic behaviors evolved because they increase the inclusive fitness of the animal providing help.

Voluntary behavior with the intent to help other people is called prosocial behavior. Why do people help other people? Is personal benefit such as feeling good about oneself the only reason people help one another?

Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.

Organisms must balance energy intake with the energy required for growth, maintenance, and reproduction. These trade-offs result in a variety of survivorship and reproductive strategies, including semelparity and iteroparity. Semelparous species reproduce only once in their lifetime, often investing most available resources into that single reproductive event. Iteroparous species, by contrast, reproduce multiple times over their lifetimes, typically allocating fewer resources to any single...

Infants often form early attachments to older siblings, using them as a source of comfort during distress. As infants become more mobile, sibling conflict commonly increases over toys, personal space, and parental attention, particularly after about 18 months.Conflict and Social LearningAs toddlers become more involved in family interactions, they learn which behaviors please or annoy their siblings. Although disagreements may involve rivalry or frustration, they can also promote...