Anthropologist Coren Apicella wanted to learn the role a person's voice plays in his or her attractiveness to potential mates.
Last summer, she flew halfway around the world with a tape recorder to study the Hadza people of Tanzania.
In the first phase of her research, Apicella invited a group of Hadza men into her Land Rover and recorded them saying "hello" in Swahili. Then she played some of the voices for a group of Hadza women, asking them which they preferred.
Apicella found the women preferred the men with the lower voices.
And that paralleled another of her findings. The Hadza men with deeper voices also had more children than their squeaky counterparts. But she says voice alone probably doesn't explain that.
"Why there's this relationship, we're not entirely sure yet," Apicella said. "It could be that these men have greater access to mates. Maybe these men that have deeper voices have higher levels of testosterone. Or maybe they're better hunters and they're able to bring more food home to their wives."
And what did Hadza men prefer in a voice? It turns out they found the women with higher pitch most attractive.
But surprisingly, the men said those same women wouldn't necessarily be the best food gatherers.
"We found that the men actually thought the women with the lower-pitched voice or the deeper voices were the better gatherers," Apicella said.
Still, psychologist Susan Hughes says this research suggests you can tell a great deal about a potential mate just from his or her voice.
"I think this study does speak to the fact that voices are signaling some biologically relevant information to potential mates," Hughes said — information like fertility or the ability to put food on the table.
But Hughes, a professor at Albright College in Pennsylvania, says it's unclear if men and women in all cultures would share the preferences of the Hadza.
Produced as part of NPR's Next Generation Radio project.