斯旺西大学与伊斯坦布尔大学的研究团队通过对225名新生儿的研究，发现了产前激素暴露与脑部发育之间的关联[1]。研究对象包括100名男性新生儿和125名女性新生儿[1]。研究人员测量了食指与无名指长度的比值（2D:4D比例），这一数值可反映胎儿时期相对于睾酮的雌激素暴露水平[1]。
在男性新生儿中，研究发现较高的2D:4D比例与头围较大存在关联，而这一关联在女性中未被观察到[1]。该研究成果已发表在《Early Human Development》2026年第214卷[1]，为"雌激素化类人猿假说"提供了支持证据[1]。这一假说认为人脑进化扩大与骨骼女性化特征同时出现[1]，提示产前雌激素可能在人类脑部演化过程中发挥了重要作用[1]。
Researchers at Swansea University have identified a potential link between prenatal hormone exposure and brain size development in newborns. In a study of 225 infants, including 100 males and 125 females, scientists examined the relationship between finger length ratios and head circumference [1]. The research found that among male newborns, a higher 2D:4D ratio—the proportion of index finger length to ring finger length—correlated with larger head size [1]. This ratio serves as a biological marker for prenatal exposure to higher levels of estrogen relative to testosterone [1].
The findings, published in Early Human Development Volume 214 in 2026, support the "feminized ape hypothesis," which posits that human brain expansion occurred alongside skeletal feminization during evolution [1]. Notably, researchers did not observe a similar correlation between finger length ratio and head circumference in female infants [1]. The study was conducted through collaboration between Swansea University and the Department of Anthropology at Istanbul University [1], suggesting that prenatal estrogen may have played a significant role in shaping human brain development over evolutionary time [1].