This research paper explores the genetic basis of the human sex ratio at birth, which is the proportion of males to females. It challenges a long-held scientific principle, known as Fisher’s principle, which suggests that the sex ratio should naturally converge to 50/50 through natural selection. The authors argue that previous studies were underpowered and unable to detect genetic variations in sex ratio due to significant measurement errors associated with the relatively small number of offspring per human. The research involved a large-scale genome wide association study (GWAS) using data from the UK Biobank, which yielded a single significant SNP associated with a reduced sex ratio. Despite this, the authors found that the heritability of sex ratio is effectively zero, likely due to measurement error. Through simulations of human sex ratio evolution under different selection pressures, the authors demonstrate that their observations are compatible with Fisher's principle, suggesting the possibility of multiple, but mostly small effect, sex ratio-influencing genes segregating in the human population.
Research paper:
Song Siliang and Zhang Jianzhi 2024In search of the genetic variants of human sex ratio at birth: was Fisher wrong about sex ratio evolution? Proc R Soc B 291:20241876
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