Charles Darwin, Sexual Selection | Charles Darwin's Theory of Evolution by natural selection

Charles Darwin, Sexual Selection

Charles Darwin & Evolution

In order to leave an evolutionary legacy survival is not enough. Individuals must also reproduce. Over 90% of species reproduce sexually, meaning two individuals from each sex must mate in order to produce offspring. Reproduction is expensive and can exert an additional evolutionary pressure. Darwin defined this pressure as sexual selection. Sexual selection operates through some members of a species having an advantage over others in terms of mating. It is the selection for traits that are solely concerned with increasing the mating success of an individual.

Darwin and Sexual Selection

Darwin’s findings in relation to sexual selection were published in his book The Descent of Man and Selection in Relation to Sex in 1871. Darwin observed that there are some characteristics that do not appear to help an organism adapt to its environment and are thus not explained by natural selection. He suggested that they feature in the process of sexual selection. He defined the process by saying that it ‘depends on the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction’. His observations and analysis lead to the reasoning that sexual selection works in two main ways: either through competition among members of one sex for access to members of the other sex (combat) or through choice by members of one sex for certain members of the other sex (display).

Combat

In terms of combat, males within a species compete with each other for access to the females. This leads to larger and stronger males and to the development of male ‘weapons’ in order to give them the advantage when in combat with other males. Darwin referred to many examples of this. Elephant seals and walruses are examples of the increased size and strength of males. Elephant seals annually migrate from their foraging ground to their breeding ground. The males arrive roughly two weeks before the females and they then fight to gain the best breeding site and thus attract the most females. Only the largest and strongest males are able to dominate in this competition. Roughly 90% of males end up pup-less! Examples of male ‘weapons’ include the horns of male beetles, the antlers of stags, the large canine teeth of male baboons and the tusks of male wild boar. In addition, male competition can also be more subtle. For example, when some male insects mate with a female they remove the sperm that is already present in the female as it is from previous males.

Display

‘Display’ refers to the exhibition of ornate male features to potential female mates, such as the striking, brightly coloured plumage of many male birds. Darwin suggested that this process of selection operates through female choice, whereby females choose the most striking males to mate with. This theory proposes that male ornaments are thought to be a genuine indication of the male’s vitality. The presence of a costly ornament on a male tells the female that he is genetically exceptionally healthy and thus her offspring will inherit his vitality.




Clear Books Period Piece: The Victorian Childhood of Charles Darwin's Granddaughter
Book (Clear Books)
  • Used Book in Good Condition

Darwinian sexual selection.

by spikemike

Darwinian sexual selection.
ShareThisPrintFrom the JUN/JUL 2006 issue of Seed:
Credit: Catherine Ledner
Joan Roughgarden thinks Charles Darwin made a terrible mistake. Not about natural selection—she’s no bible-toting creationist—but about his other great theory of evolution: sexual selection. According to Roughgarden, sexual selection can’t explain the homosexuality that’s been documented in over 450 different vertebrate species. This means that same-sex sexuality—long disparaged as a quirk of human culture—is a normal, and probably necessary, fact of life

Charles Darwin ... relied on group selection ...

by askaboutaa1

"Charles Darwin described both natural selection and sexual selection, and he relied on group selection to explain the evolution of altruistic (self-sacrificing) behavior. But group selection was considered a weak explanation, because in any group the less altruistic individuals will be more likely to survive, and the group will become less self-sacrificing as a whole."

Additional definitions of evolution:

by jmd1990

A theory first proposed in the nineteenth century by Charles Darwin, according to which the Earth's species have changed and diversified through time under the influence of natural selection. Life on Earth is thought to have evolved in three stages. First came chemical evolution, in which organic molecules were formed. This was followed by the development of single cells capable of reproducing themselves. This stage led to the development of complex organisms capable of sexual reproduction. Evolution is generally accepted as fact by scientists today, although debates continue over the precise mechanisms involved in the process

You might also like

Help the Darwin Foundation Help Galapagos  — Huffington Post
Please join us for a special celebration of a half-century of groundbreaking scientific research and conservation by the Charles Darwin Research Station, the oldest, largest, and most successful scientific institution in the Galapagos Islands.

FAQ

Ray Eston Smith Jr
What are the fundamental laws of social morality?

Here's what I think:

First Law. Don't initiate force or fraud. This is absolutely true because people will not voluntarily associate with anyone who coerces or defrauds them. If a group of people don't obey this law, then they aren't voluntarily associated, therefore they are not a society, therefore social morality does not apply to them, anymore than it applies to rocks and trees.


Second Law. There are no other laws, because any other law would violate the first law.

Note: I am distinguishing between social morality, which people…

I don't think there are really any laws of social morality it is just social order.

Few scientists and religious scholars have seriously pondered how science and religion can be reconciled. But times are changing. Not long ago I attended two meetings that brought together scientists, theologians, and religious scholars to discuss just that issue. The first gathering was part of the Science and the Spiritual Quest II program ( sponsored by the Center for Theology and the Natural Sciences in Berkeley, California. The other was organized by the American Association for the…

Related Posts