A farm in Miami, Florida, is currently home to an emu.

In a recent study published in the Proceedings of the National Academies of Science, researchers led by Patricia Brennan of the University of Massachusetts-Amherst discovered a link between being a good father and smaller-than-average testicle size.

The study, which involved 70 men from Atlanta, found that men with smaller testicles showed more "nurturing-related" brain activity when shown images of their own children. This research adds to the growing body of work focused on the male half of the species and their role in reproduction.

Reproduction is where evolution makes its mark, and studies like this one are interested in understanding the factors that contribute to reproductive success. However, it's important to note that a 2012 study published in the Journal of Urology did not repeat the findings of the current study regarding parenting implications.

This new study is not the first to delve into the mysteries of male biology. Scholars have often turned their attention to the subject, from studies of drakes to dudes. In fact, an international team suggested in April that size matters for male attractiveness, based on a study of Australian women.

Interestingly, the study of male genitalia has attracted political interest as well. In March, U.S. politics watchdog Politifact determined that Yale ornithologists received federal research money to study the curiously long, corkscrewed genitalia of ducks. The allegation was rated "Mostly True" by Politifact, following a challenge on the grant's propriety on the Twitterverse.

It's worth mentioning that a 2012 Journal of Urology study of 116 Houston men found no connection between smaller-than-normal testicle size and testosterone levels or penis size. Instead, the study found a connection between hormone levels and the anatomy of their backsides.

Meanwhile, a 2011 Nature study showed that evolution deleted the genes responsible for penile "spines" seen in chimps from the human genome, also removing human tactile whiskers found on apes.

While the current study does not provide new information about the connection between male genitalia and attractiveness or reproduction, it does add to our understanding of the complex interplay between biology and parenting. As research continues, we can expect to learn more about the role of testicle size in fatherhood and the evolution of the male species.