Generous hips, a thin waist, a voluminous chest: in the collective imagination, these shapes would be the signature of a “very fertile” woman. Many pseudo-scientific discourses even assert that men have evolved to detect, at a glance, the capacity of a partner to have many children. Behind this idea, a promise that is reassuring for some, distressing for others: the body would give a “biological fertility score”. A large systematic review published in 2025 in the journal Evolutionary Human Sciences However, this seductive story is dampened. And their results are surprising, as much for what they show as for what they don’t find.
Do wide hips and full breasts really predict fertility?
Psychologists Linda H. Lidborg and Lynda G. Boothroyd compiled 19 studies, bringing together 31 samples from 16 countries and more than 125,000 women, to check whether
female physical characteristics specific data actually announce the number of children, pregnancies or grandchildren, or the survival of children.
Small reminder: the theory of sexual selection assumes that certain bodily traits, accentuated in women, would have been favored because they signal a strong
fertility. On average, women have a lower waist-to-hip ratio, more fat on the hips and buttocks, permanent breasts, a higher-pitched voice, less muscle mass, and a higher 2D:4D ratio (longer index finger to ring finger) than men. According to this theory, men would prefer these traits because they indicate that a partner can conceive more easily and have more children over the course of her life.
To test this idea, Linda H. Lidborg and Lynda G. Boothroyd surveyed available work. “Evolutionary researchers have long argued that heterosexual men are attracted to ‘feminine’ traits in women, such as more feminine facial features, a curvy body, and a thin waist, because these traits might signal higher fertility.“, she explained to PsyPost. The team selected studies that measured breast size, waist-to-hip ratio, voice, physical strength or 2D:4D ratio, and compared them to direct indicators: number of children, pregnancies, age at first and last child. No study linked facial femininity to observed fertility.
Hips, breasts, voice, fingers… Fertility signals that are ultimately very uncertain
The results do not confirm the classic scenario according to which very feminine forms would guarantee greater reproductive success. For the waist-hip ratio, eight studies show that women with a higher ratio, and therefore with a less “hourglass” silhouette, often had more children. The authors mainly see the imprint of pregnancies: the size widens after several births. Only one study that measured this ratio before any childbearing found no link with the subsequent number of children.
For the other traits, the observation is just as cautious. The three samples that tested breast size resulted in alternately positive, negative or non-existent links with the number of children. Two small studies on voice pitch show, again, an effect present among Himba women in Namibia but absent among the Hadzas in Tanzania. Finally, 7 studies on the 2D:4D ratio only note a few very weak correlations, while this ratio is almost never invoked as a criterion of attractiveness.
Why the female traits-reproductive success link remains to be proven
In conclusion, this research indicates that current evidence is not sufficient to support the idea that female physical traits are reliable indicators of reproductive capacity. The widely accepted evolutionary hypothesis that men prefer these traits because they signal fertility lacks strong empirical support. moreover, most studies on the subject are based on a small number of participants and sometimes from industrialized countries where contraception is widely used (which masks the natural links between biology and reproduction, family size being more a choice than the sole reflection of reproductive capacities).
“Current data does not demonstrate that women with more feminine features are more fertile than those with fewer features.Lidborg told PsyPost. “This does not mean that the link does not exist, just that, as of yet, there is no evidence to support it. In our article, we recommend caution in repeating this hypothesis, due to lack of sufficient evidence to date.”.