positive assortative mating

Positive assortative mating, also known as homogamy, is a form of nonrandom mating where individuals choose partners with similar observable characteristics (phenotypes). This can include preferences for similar religious, cultural, or ethnic backgrounds, professional interests, or physical traits. For instance, a tall person might be more likely to choose a tall partner. This type of selection is common in both human and nonhuman populations, where phenotypic similarity plays a role in mate selection. The opposite, negative assortative mating, occurs when individuals avoid mating with those who are similar to them.1