Dating coupling and mate selection Dirty girls only chat room
Males must fight, in the form of intra-sexual competition, for the opportunity to mate because not all males will be chosen by females.
This became known as Bateman's principle, and although this was a major finding that added to the work of Darwin and Fisher, it was overlooked until George C.
Fifteen years later, he expanded this theory in a book called The Genetical Theory of Natural Selection.
There he described a scenario where feedback between mate preference and a trait results in elaborate characters such as the long tail of the male peacock (see Fisherian runaway).
Though this particular mechanism operates on the premise that all phenotypes must communicate something that benefits the choosy mate directly, they can still have unintentional indirect benefits to the mom by benefiting the offspring.
For example, with the increased help in feeding their young seen in Northern Cardinals with more plumage brightness, comes an increase in the overall amount of food that is likely to be given to the offspring even if the mother has more children.
The differences in levels of parental investment create the condition that favours mating biases.
Darwin proposed two explanations for the existence of such traits: these traits are useful in male-male combat or they are preferred by females. Darwin treated natural selection and sexual selection as two different topics, although in the 1930s biologists defined sexual selection as being a part of natural selection.
One example of a sexually selected trait with direct benefits is the bright plumage of the northern cardinal, a common backyard bird in the eastern United States.
Male northern cardinals have conspicuous red feathers while the females are more cryptic in coloration.
Williams emphasised its importance in the 1960s and 1970s.
In 1972, soon after Williams' revival of the subject, Robert L. Trivers defined parental investment as any investment made by the parent that benefits his or her current offspring at the cost of investment in future offspring.