Prenatal testosterone in womb leads to "masculine" facial features: Australian study

Australian researchers have found masculine facial features -- for both men and women -- are dependent on the level of testosterone babies are exposed to in the womb.

The research findings, published in the Royal Society journal Proceedings B on Wednesday, are the first established link between prenatal testosterone levels and physical facial features.

"It was quite a breathtaking effect," co-author of the study Professor Andrew Whitehouse, from the Telethon Kids Institute at the University of Western Australia, told the Australian Broadcast Corporation (ABC) on Wednesday.

The facial features leading to more masculine looks in both sexes, according to researchers, were wider noses, eyes and foreheads.

Whitehouse told the ABC that while it would seem manifestly obvious that testosterone, the main male sex hormone, produced masculine features in humans, until now there was no concrete evidence to support the theory.

The study took place over two decades, with researchers recording the level of testosterone in the umbilical cord blood of 97 male and 86 female newborns.

Once the children had reached 21 to 24, when the facial features become fully formed, researchers assessed their face for masculine qualities.

"Higher levels of testosterone in the cord blood are actually related to more masculine facial features," Whitehouse said.

"That holds within sexes as well. So if we look at just females we find that females with more testosterone have more masculine features as well."

Three-dimensional (3D) photography was used to determine the degree of masculinity in each face, with digital measurements recorded between key"landmark"points.

Whitehouse said the level of the hormone in the womb is mostly influenced by genetic makeup, but environmental factors -- such as the mother being overweight -- also play a role. Endi