Digit ratio (2D:4D) and neonatal head circumference: Evidence for oestrogenization in human brain evolution?

科学分野:

• Developmental biology; Human evolution; Prenatal development

背景:

• The second-to-fourth digit ratio (2D:4D) is a recognized marker of prenatal sex steroid exposure.; 2D:4D ratio has been associated with various physical and behavioral traits, including intelligence.; Limited research exists on the association between neonatal 2D:4D and head circumference.

研究 の 目的:

• To investigate the relationship between neonatal 2D:4D and head circumference.; To explore sex-specific associations between 2D:4D and head circumference.; To examine the influence of prenatal hormone exposure on neonatal head development.

主な方法:

• A sample of 225 full-term newborns (125 girls, 100 boys) was analyzed.; Measurements included recumbent length, weight, head circumference, and digit lengths (2D and 4D).; Hierarchical multiple linear regression was used for sex-specific analyses, with maternal education as a covariate.

主要な成果:

• In males, right 2D:4D and recumbent length were positively associated with head circumference.; In females, recumbent length and birth weight predicted head circumference; digit ratios and maternal education showed no association.; Variance in head circumference was greater for male newborns compared to females.

結論:

• Neonatal right 2D:4D is positively correlated with head circumference, most strongly in boys.; This association is independent of recumbent length and weight, suggesting a direct link to prenatal factors.; Findings support the role of prenatal oestrogenization in head development and its potential implications for intelligence.