Not All Sex Differences Are Created Equal

Why do some species have more physical sex differences than others?

• Sexual dimorphism refers to physical sex differences within a species.

• Species with more sexual competition are more sexually dimorphic.

• Species that pair bond are less sexually dimorphic.

Humans are sexually dimorphic, which means that males and females are, on average, different sizes. In humans, like most sexually dimorphic species, males are typically larger than females. Why does this sex difference not go in the opposite direction, and why are all species not equally sexually dimorphic? The explanation is the same as most things in nature: energy.
Not All Sex Differences Are Created Equal