Conversely, an individual lacking facial symmetry will strive for symmetry with a symmetric hair style and symmetric tattoos and piercings. Based on this, we designed a study to test for these factors. This study was conducted to examine the mating preferences of heterosexual and homosexual males and females. It is important for society to understand the differences and similarities between sexual orientations. Darwin's evolutionary theory of human mate selection suggests that males and females seek out mating partners who provide the means to enhance their own reproductive success, and the specific traits vary as a function of sex.
Evolutionists theorize that homosexuality serves adaptation in terms of altruism and kin selection.
Additional research suggests that homosexuality is simply a reversal of the opposite heterosexual roles. It is not clear how natural selection may have directly favored a preference pattern that would undermine reproduction, and a number of findings consider the biological status of homosexuality a puzzle. Singles personal advertisements posted on the Internet networks during a four week span of time were analyzed. There was a significant effect of sexual orientation and a significant sexual orientation x gender interaction. Overall, homosexuals preferred younger partners than did heterosexuals.