In the cover story of Current Biology’s new issue, the research team provides the first evidence of a tradeoff between two traits evolved by different howler monkey species so that males could mate with females and pass their genes to offspring: large gonads to make more sperm, or a large vocal-tract hyoid bone to produce a deep call that scares competitors and attracts females – similar to how women like deep male voices.
“They are different solutions to the same problem,” says...
