Related Experiment Video
Updated: Aug 15, 2026

Using a Comparative Species Approach to Investigate the Neurobiology of Paternal Responses
Published on: September 19, 2011
Violent men have more sons: further evidence for the generalized Trivers-Willard hypothesis (gTWH)
1Interdisciplinary Institute of Management, London School of Economics and Political Science, Houghton Street, London WC2A 2AE, UK. s.kanazawa@lse.ac.uk
Abstract:
The generalized Trivers-Willard hypothesis (gTWH) [Kanazawa, S., 2005a. Big and tall parents have more sons; further generalizations of the Trivers-Willard hypothesis. J. Theor. Biol. 235, 583-590] proposes that parents who possess any heritable trait which increases the male reproductive success at a greater rate than female reproductive success in a given environment have a higher-than-expected offspring sex ratio, and parents who possess any heritable trait which increases the female reproductive success at a greater rate than male reproductive success in a given environment have a lower-than-expected offspring sex ratio. One heritable trait which increases the reproductive success of sons significantly more than that of daughters in the ancestral environment is the tendency toward violence and aggression. I therefore predict that violent parents have a higher-than-expected offspring sex ratio (more sons). The analysis of both American samples and a British sample demonstrates that battered women, who are mated to violent men, have significantly more sons than daughters.
Related Concept Videos
The Y Chromosome Determines Maleness
Evolution
Around 300 million years ago, the two sex chromosomes diverged from two identical autosomal chromosomes. Over time, the Y chromosome has lost most of its genes, shrinking in size. Today,...
X-linked Traits
X-linked Traits
Sex-linked Disorders
X and Y Chromosomes
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...
Criticisms of the Evolutionary Perspective
Evolutionary psychology provides one explanation for these findings, suggesting...

