The variability hypothesis, aka the greater male variability hypothesis states that males experience greater variability in traits than females. This includes more variability in sexual preferences, social attitudes, behaviours, intelligence, strength, other physical traits, genetic variation, etc...
History of the hypothesis
The idea of men being more intra-sexually heterogenous than women in physical traits dates back to at least Charles Darwin, who stated his belief in such in The Descent of Man and Selection in Relation to Sex.
Sexologist Havelock Ellis famously expanded on this to include mental traits being more variable among men than women, in, "Man and Women: A study of human sexual characters" where he wrote
By the 1890’s several studies had been conducted to demonstrate that variability was indeed more characteristic of males...The biological evidence overwhelmingly favored males as the more variable sex.
- The variability hypothesis: The history of a biological model of sex differences in intelligence". Signs. 7 (4): 769–797. doi:10.1086/493921. JSTOR 3173639.