T/F: Males Are Larger Than Females

Males Are Larger Than Females, Or Are They? New Data Challenges 100 Years Of Bias

Think of a lion; think of a gorilla; think of an otter. In your head, are the males bigger than the females? Well, a new study is set to challenge over 100 years of bias in this area of research. By looking at over 400 mammal species, the team found some surprising results – in most cases, the males of the species are not bigger than the females...

Back in the 1970s, mammologist Katherine Ralls found that there were many species in which there was little sexual size dimorphism (SSD), especially within the larger groups of mammals. However, her research was overlooked [ed: surprise??] and overpowered by the idea that the males of most mammalian orders are bigger than the females...

They [Nature study (vide infra)] suggest that the idea that males are larger than females has persisted for so long because a lot of early zoology work was based on male competition for mates. The team also suggest that their results could change again as more data is collected, and suggest more work be carried out in female biology across a wide range of mammalian species.

https://www.iflscience.com/males-are-larger-than-females-or-are-they-new-data-challenges-100-years-of-bias-73347

"New estimates indicate that males are not larger than females in most mammal species"

Abstract

Sexual size dimorphism has motivated a large body of research on mammalian mating strategies and sexual selection. Despite some contrary evidence, the narrative that larger males are the norm in mammals—upheld since Darwin’s Descent of Man—still dominates today, supported by meta-analyses that use coarse measures of dimorphism and taxonomically-biased sampling. With newly-available datasets and primary sources reporting sex-segregated means and variances in adult body mass, we estimate statistically-determined rates of sexual size dimorphism in mammals, sampling taxa by their species richness at the family level. Our analyses of wild, non-provisioned populations representing >400 species indicate that although males tend to be larger than females when dimorphism occurs, males are not larger in most mammal species, suggesting a need to revisit other assumptions in sexual selection research.

https://www.nature.com/articles/s41467-024-45739-5