New research has tied a drop in testosterone some 50,000 years ago to an increase in art and advanced tools.

According to a press release from Duke University, scientists suggest in a new study, published in the journal Current Anthropology, that a change in humans' skulls was an indicator of testosterone. The cultural shift took place about the same time as the decrease in testosterone.

"The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament," study lead author Robert Cieri, a biology graduate student at the University of Utah, said in the release.

For their study, which Cieri started at Duke, the team measured 1,400 skulls of modern and ancient humans. In addition to a cultural shift, the scientists said lower testosterone levels led to an increase in general kindness as well.

"If we're seeing a process that leads to these changes in other animals, it might help explain who we are and how we got to be this way," Brian Hare, an animal cognition researcher at Duke, said in the release.

One of the most noticeable evolutionary changes in the skulls was a heavy, protruded brow went away and rounder heads became more common. While the researchers could detect testosterone levels, they could not determine if the humans had less receptors or if the hormone just went away.

The study authors examined 13 skulls of modern humans older than 80,000 years, 41 aged between 10,000 and 38,000 years old. Lastly, they examined 1,367 skull samples from the 20th century from 30 different populations.

"If prehistoric people began living closer together and passing down new technologies, they'd have to be tolerant of each other," Cieri said. "The key to our success is the ability to cooperate and get along and learn from one another."