Still, the hypocrisy of sexual repression is blatant in historic underwear, which at once prudishly hid the female body while exaggerating its sexual traits: breasts hiked up, hips widened, butt enlarged.
In many species, condition-dependent secondary sexual traits are important for female choice.
Male secondary sexual traits and female mate choice traits must contain heritable variation for sexual selection to operate.
Plus, Sara Mitchell discusses the coevolution of sexual traits in mosquitoes and their influence on malaria transmission.
Only in the past 20 years have researchers begun to glean how sexual traits can reflect a male's vitality.
We used full-sib mating to investigate the effects of inbreeding on viability, attractiveness, morphology and potentially secondary sexual traits in male and female zebra finches, Taeniopygia guttata.
To complicate matters, both male sexual traits and female mate choice typically show condition dependence, implying that environmental effects probably play an important synergistic role.
"A lot of closely related species differ in sexual traits," says Emily Ellis, an evolutionary biologist at the University of California (UC), Santa Barbara.
That makes the narwhal tusk similar to sexual traits in other animals, such as a stag's antlers or a peacock's feathers, that are used to attract females.
Surprisingly, they have not been examined for bright coloration, one of the most prominent sexual traits.
Various models of sexual selection have been put forward to explain the origin and maintenance of elaborate male secondary sexual traits.
