Evolutionary Explanations

In addition to natural selection what else does Darwin believe man has evolved through?

Sexual Selection

What is sexual selection?

The process by which mates are picked

What is Anisogamy?

Differences between male and female sex cells. It refers to the unequal size and investment of gametes, where females typically produce larger, fewer eggs and males produce smaller, numerous sperm.

What do these differences in sex cells mean?

They influence reproductive strategies and behaviors, leading to different mating patterns and competition between sexes.

What are the male strategies for reproductive success?

Having sex with, and impregnating, as many women as possible (they will never know for sure if the child is theirs)

What are the female strategies for reproductive success?

needs a partner that will be committed to the relationship in the long run and provide resources for her and the child, ensuring the child’s survival - this is due to the energetically expensive process of producing an egg and carrying the child in the womb for nine months.

What is Dimorphism?

Differences between males and females.

What is intra-sexual selecation?

Where a member of the same sex competes against each other to gain mating access to members of the opposite sex (more likely - yet not always - used by males.

Why do males use intra-sexual selection?

They have a small parental investment in rearing their offspring so best strategy is to try and mate with as many females to pass on their genes.

In order to do this they must have competed against each other for the right to mate with females.

Victor gets to pass on genetics to offspring.

What is Inter-sexual selection?

Where a member of one sex picks a member of the other sex for the purpose of mating (more likely but not always used by females).

Why do females use inter-sexual selection?

Females have to invest heavily in caring for their offspring and have few chances to reproduce so they have to make sure they select the right male to mate with to pick the best father for her offspring.

If she picked a strong mate then her genes will in-turn have the best chance of being passed on because there are less likely to be weaknesses or defects in her offspring.

The female needs resources for her during pregnancy and while raising the children.

Why may males use inter-sexual selection?

To pick the most fertile female.

What are sexual indicators used for?

To instinctively select the best mate.

What sexual indicators are common for females to search for?

Testosterone, square jaw, deep voice, ‘V’ shape body, and a heavier brow.

What sexual indicators are common for males to search for?

‘Hourglass’ figure, child-like face (large eyes, small nose, full lips), indications of youth and fertility. - evidence of success in child bearing & rearing

Ronald Fisher (1930) - Sexy Sons hypothesis.

A female mates with a mate who has a desired characteristic, and this ‘sexy’ trait is inherited by her son. Increases likelihood successive generations of females will mate with her offspring.