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Updated: May 27, 2025
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Intrasexual Selection for Upper Limb Length in Homo sapiens.
Neil R Caton1, David M G Lewis2,3
1School of Psychology, University of Queensland, Brisbane, Queensland, Australia.
Summary
Greater upper limb length provides a competitive edge in human contests, particularly for males. This study reveals longer limbs are linked to combat success and significant sexual dimorphism in Homo sapiens.
Area of Science:
- Evolutionary biology
- Human anatomy
- Behavioral ecology
Background:
- Sexual selection drives the evolution of physical traits for competitive advantage.
- Weaponry in appendages aids in overpowering opponents during contests.
- Upper limb length is a potential indicator of competitive success.
Purpose of the Study:
- To determine if greater upper limb length enhances success in human contest competition.
- To explore mechanisms linking upper limb length to competitive outcomes.
- To investigate sexual dimorphism in upper limb length in Homo sapiens.
Main Methods:
- Collected fight statistics and images from 715 professional Ultimate Fighting Championship (UFC) combatants.
- Analyzed upper limb length and sexual dimorphism across diverse populations (N=6915) in four separate studies.
- Controlled for allometry and biacromial width to accurately measure upper limb length.
Main Results:
- Increased upper limb length correlated with higher success rates in intrasexual contests.
- Longer limbs facilitated both submission grappling and knockout victories.
- Consistent cross-cultural evidence showed men possess longer upper limbs than women.
Conclusions:
- Upper limb length may be a trait shaped by sexual selection through contest competition.
- Findings have implications for understanding human evolution, anthropology, and psychology.
- Intrasexual selection appears to exert stronger pressure on male upper limb length.
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