How did human genitalia evolve?

It has long been believed that humans evolved smooth penises as a result of adopting a more monogamous reproductive strategy than their early human ancestors. Those ancestors may have used penile spines to remove the sperm of competitors when they mated with females.

How are differences in genitalia morphology produced in evolution?

Three main hypotheses have been proposed to explain the evolution of genital morphology: the lock and key, the pleiotropy and the sexual selection hypotheses. In this sense, it has been suggested that differences in genital morphology between closely related species would be largely polygenic [16].

How does genitalia morphology used to determine the species?

The genital morphology of animals with internal fertilization shows diversity among species, often more so than their external morphology (1). The shape and size of these genital parts match and are species specific, and their lengths show correlated evolution between the sexes toward exaggeration (Fig.

What are the causes and consequences of genitalia evolution?

Although receiving minimal research to date, ecology may influence genital evolution through four major routes: (1) eliciting direct natural selection on genital morphology, (2) influencing sexual selection on genitalia, (3) causing selection on traits genetically correlated with genitalia, and (4) exerting effects on …

Why do animals have complex genitalia?

Males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes. In some bed bug species, the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them.

What is Gametic isolation?

Gametic Isolation: Reproductive Isolation where mating does occur, but male and female gametes cannot bind to form a zygote. For example, surface proteins on the eggs of one species prevent sperm of the wrong species from entering.

What is hybrid sterility?

Hybrid sterility is defined as the inhibition or suppression of the reproductive capacity of F1 or later generation hybrids between genetically different strains or populations, usually belonging to different species. Sterility of hybrids between species is merely one of the reproductive isolating mechanisms.

What is a behavioral barrier?

Behavioral barrier means a system that utilizes a stimulus to take advantage of natural fish behavior to attract or repel fish. A behavioral barrier does not offer a physical impediment to fish movement, but uses such means as electricity, light, sound or hydraulic disturbance to move or guide fish.

What is gamete mortality?

Gamete mortality (physiological isolation)—type of pre-zygotic reproductive isolation mechanism in which gametes die before a zygote can be formed, usually because sperm are unable to survive in the female reproductive tract of members of the wrong species.