Group-selection theory is a proposed evolution of mechanism, whereby natural selection is perceived to act at the group level, rather than at a conventional individual level.
Xenophobia: This is a human behavior that props up group-selection theory. This is because, all things being equal, people choose to be with other people who look like them, speak similar dialect or hold the same beliefs or values. These groups of individuals prefer to co-operate with people who have common or related behaviors (Ashford and LeCroy). For instance, a particular group of individuals is competing with each other for a certain commodity such as food, one group might prefer to be wary of those belonging to other groups, thus resulting in xenophobia.
Human Behavior that Supports Gene-selection Theory
This theory holds that, adaptive evolution happens through differential endurance of competing genes (Degler). Due to recombination and crossing over that results to shuffling of genes, it is the genes that are chosen for over time. It is also referred to as the selfish human behavior, due to its selfish goals that tend to achieve individual interests.
Kin Selection: Individuals will prefer to favor other individuals that posses the same genes, or are related in a way, for instance, siblings or relatives (Ashford and LeCroy). For example, if an individual possesses a certain gene, there is a probability of them jumping into a flooded river to save their downing child, brother or sister. In this case, that individual prefers to save their own in order to retain the gene in the population. In addition, another individual who does not possess the same gene can possibly stand aside on the river bank, watching the individual drown.
Ashford, José B, and Craig W. LeCroy. Human Behavior in the Social Environment: A Multidimensional Perspective. Australia: Brooks/Cole, Cengage Learning, 2013. Print.
Degler, Carl N. In Search of Human Nature: The Decline and Revival of Darwinism in American Social Thought. Cary: Oxford University Press, Incorporated, 2005. Internet resource.