Sexual Selection Flashcards
Reproductive rates in Men
A man could reproduce much faster than a woman could
If a man made little commitment to rearing
If a man had multiple partners
Reproductive Rates in Women
Having multiple partners would not increase a woman’s reproductive rate
Mating Systems: Monogamy
a mating system in which males and females each have only a single reproductive partner
Mating Systems: Polyandry
a mating system in which women may have more than one reproductive partner
Polygyny
a mating system in which men may have more than one reproductive partner
Is monogamy the norm
Is monogamy the norm?
85% of human societies allow polygyny
Most of the more than 1,000 societies that permit polygyny are small tribal groups
Prohibitions on polygyny are recent
Historical records suggest that prohibitions date nowhere more than 500 years
Marriage practices are not a perfect reflection of mating practices
Marital infidelity
Divorce and remarriage
Parental investment
anything a parent does for a particular offspring that both increases that offspring’s reproductive prospects and decreases the parent’s reproductive prospects
A limited resource, like income or allowance
What you spend on one thing is not available for something else
Ex. gestation, lactation, groceries, medical fees, clothing, tuition, time spent, etc.
Biparental investment
When both sexes of parent contribute significant amounts of parental investment
The norm in human populations
If males could accelerate their reproductive rate by acquiring more mates, why do they slow themselves down by investing in offspring?
Human Parental Investment
Under certain conditions, offspring who receive investment from two parents do much better than offspring who receive it from only one
Biparental investment is more likely to evolve in species with helpless young
Extreme dependence of human infants may have favored the evolution of biparental investment in our species
Dynamics of Mating Competition
Members of the fast sex compete, while members of the slow sex choose
The more the investment, the more at stake
In a monogamous species, females and males tend to be equally competitive and equally choosy
Humans are neither strongly polygynous nor fully monogamous
Both sexes will evolve to compete for mates, with competition being more intense in males
Both sexes will evolve to be choosy about their mating partners, with women being more selective
We would predict that women will be more choosy and men more competitive
Buss and Schmidt (1993)
Asked men and women to rate how likely they would be to consent to sexual intercourse with someone they viewed as desirable, given that they had known the person for various periods of time
Participants rated their willingness on a scale from -3 (definitely not) to +3 (definitely yes)
Men consistently indicate a greater willingness to engage in sexual intercourse than women do
Choosiness / Homosexuality
For a heterosexual male, this is a problem…
The people with whom he must negotiate his sexual desires are women, whose desires differ
Homosexual men negotiate with individuals whose desires are more coincident
Thus, we would expect that homosexual men would be more successful in achieving large numbers of sexual partners than heterosexual men
Homosexual men report having hundreds or even thousands of partners.
Lesbian and straight women do not differ on average in their numbers of sexual partners
Donald Symons (1995)
“Beauty is in the adaptations of the beholder.”
Nothing in and of itself is intrinsically beautiful
We find this beautiful (and not beautiful) because it was (or was not) adaptive for us to in the EEA
Mates provide two kinds of resources
Good Genes
Good Investment
The best mates are the ones that provide both good genes and good investment.
How do we know which mates have the best genes and will provide the best investment?
Sex and Anisogamy
A comprehensive definition is that males produce small gametes (sperm) that seek out the larger, less mobile gametes (eggs) produced by the female.
