Basso Profundos

The NY Times reports on a study of howler monkeys that found that to gain a mating advantage, species evolved either to make very low-frequency sounds, or have much larger testicles, but none had both. It seems to show a clear trade-off. Can't have it both ways! A researcher acknowledged that taking measurements is not the easiest thing to do. Full article referenced below is obviously TMI!
tjs
http://www.nytimes.com/2015/10/23/science/howler-monkey-species-deep-voice-testicle-size.html?ref=world