Introduction
Darwin’s theory of evolution explains that natural selection favors
organisms with a high probability of survival and the ability to pass
genes down to their offspring through reproduction
(Darwin, 2008). This theory
is widely accepted and has become a core part of any course about
evolution. Darwin’s (1871) theory of evolution suggests that individuals
of high ‘fitness’ will pass their genetics to offspring by mating with
individuals with gametes compatible for fertilization (e.g., egg and
sperm). Same-sex behavior (SSB) often does not lead to reproduction, yet
it has been documented in over 1500 species of animals (Monk et al.,
2009).
Scientists have long searched for a genetic explanation for same-sex
behavior in humans, aiming to find a gene or genetic trait that can be
inherited and passed down to offspring. Most of these studies have come
up short, with little to no evidence of a “gay gene”
(Harris, 2019). This further
confuses scientists that seek to understand how same-sex behavior
evolved without any apparent “benefits.” We must also consider that
different-sex behavior (DSB) is not always initiated for reproduction
purposes. However, this costly sexual activity is prevalent among most
organisms. Why do we differentiate between same-sex and different-sex
behavior if neither leads to reproduction?
Monk et al. (2019) offer an alternative perspective of the origins of
same-sex behavior from being a ‘Darwinian paradox.’ Under Darwin’s
theory, the biological costs of same-sex behavior would have eradicated
it over time because of a lack of reproductive benefits. Monk et al.
(2019) explain how same-sex behavior and different-sex behavior evolved
together instead of SSB evolving from DSB. When male-female, monogamous
relationships are used as the baseline for animal mating behavior,
same-sex behaviors are seen as abnormal or unusual. The understanding
that male-female relationships are the norm and default is known as
heteronormativity. This can harm the research of these animals and any
queer person that adopts this mentality. If we shift our perspective to
view same-sex behaviors as normal, we can reconceptualize biological sex
and sexual activity in animals and prevent bias in research.