WHILE men with deep voices may seem more masculine to women, a lower pitch doesn’t indicate great sperm quality.
In fact, a recent UWA study shows men whose voices were rated as more attractive tended to have lower concentrations and poorer quality sperm.
The outcome refutes the phenotype-linked fertility hypothesis, which proposes that male secondary sexual characteristics give females a clear signal of who is an optimal mate.
“In addition to being perceived as attractive, men with low pitched voices are judged to be stronger, larger, better fighters and providers, and more, and these judgments have been found to hold reasonable validity within western and hunter-gatherer societies,” say co-author Prof Leigh Simmons of UWA’s Centre for Evolutionary Biology.
“[However] the negative impact on semen quality of men's expenditure on physical training is well documented, where extreme investments in physical strength have been shown to affect the hypothalamus-pituitary-testes axis.
“It is thus possible that investments in traits that contribute to dominance as well as attractiveness may come at the cost of reduced sperm quality.”
In short, acquiring mating opportunities takes precedence over optimising sperm production – a trade-off well documented in domestic fowl, arctic char, field crickets and cockroaches.
Published in PLoS ONE, the study involved 54 heterosexual Caucasian males between the ages of 18 and 32.
Participants completed a questionnaire regarding lifestyle factors that could impact their sperm quality, including alcohol and caffeine consumption, illicit drug use, dietary habits, frequency of sexual activity and potential exposure to xenobiotics.
These variables were later factored into outcome models.
Semen collection was performed at home with delivery to the lab within one hour. Participants had to abstain from sex for 48 hours prior to ejaculation, though no longer than six days.
Semen was examined for concentration of sperm cells as well as seven motility parameters shown to indicate fertility. These included velocity measurements, straightness of pathway and lateral amplitude of sperm head movement.
Voice recordings of the participants saying a, e, i and o were analysed for pitch, and ranged between 85.3 to 134.2 Hz.
Notably, no significant relationship was found between a man’s pitch and his height, weight, testes volume or age.
The recordings were then rated individually for attractiveness and masculinity by a group of 30 heterosexual Caucasian females between the ages of 18 and 30.
While women consistently rated low-pitched voices as both more attractive and more masculine, the sperm behind those baritone intonations didn’t manage to live up to their billing.