Lecture 3 Sneaky Sex: The Evolution and Endocrinology of Mating Systems Flashcards
What is a mating system?
A social structure, used to maximise reproductive output
What is “solitary” mating system?
Only seek a mate for the breeding season, otherwise lives individually
What is a “monogamous” mating system?
A male and female pair exclusively for most of their lives to raise young
What is a “polygamous” mating system?
One individual pairs with multiple members of the opposite sex
What is a “polygynous” mating system?
‘gyn-‘ means women, so one male to more than one female
What is a “polyandrous” mating system?
‘andr-‘ means men, so one female to more than one male
What is harem mating?
An extreme example of POLYGYNY (one male has a harem of many females)
What is co-operative breeding?
Many males and females associate together but only a few individuals in the group breed. Other individuals have suppressed reproductive activity, this increases success rates of rearing young
What is the history and current human mating system?
Early humans in the hunter-gatherer period were monogamous/polyandrous/polygynous.
Shifted to nomadic/farming period, became polygynous because men worked and had more power.
Then became more sedentary and more secure monogamy. Monogamy increases when more resource-rich, because babies more likely to survive so did not need to give birth to so many
What is the immunocompetence handicap?
More visual signals like colour or horns are more exposed to predators and frequently have lower immunity because testosterone downregulates cytokines
How are visual signals regulated in males and females respectively?
Raised testosterone and oestrogens respectively induces species-specific secondary sexual characteristics
What are pheromones?
Chemicals that produce a behavioural or physiological response in an organism
Which sex steroids and complex proteins are the olfactory signals reliant upon in the male and female?
Male: testosterone is converted to the 17-ketosteroids (DHEA, androstendione, estrone)
Female: oestradiol and oestrone is convered to oestriol
How are sex steroids excreted?
Conjugated to sulfuric acid or glucaronic acid, then excreted in faeces or urine.
Is female competition more or less advantageous than males?
Usually less advantageous because males have to fight over reproductive partners and resources etc. more important because often more dominant role in societal structures.
What are the advantages of female competition?
Establish dominance hierarchies so conflict is reduced.
May remove a reproductive rival
What are the disadvantages of female competition?
Female or their young may be fatally injured. Especially since female murder the young that are not theirs to establish their dominance and reduce stress on resources.
What is the suppression of reproduction?
Suppression of reproduction occurs in multi-member mating systems especially in cooperative breeding, as dominant breeding pair can suppress reproduction of subordinate females by urinary pheromones
What is the function of male competition?
Establish dominance hierarchies
Establish mating priority
Establish territories and resources
What are the advantages of male competition?
May remove a reproductive rvial
What are the disadvantages of male competition?
Fatal injuries. Murder the young of others to ensure paternity.
What are some mechanisms of signalling in humans?
Humans choose partners with dissimilar human leukocyte antigen (HLA) presented on the MHC (major histocompatibility complex). Maximise immune robustness.
Pheromones in the apocrine secretions. Pheromones change with menstrual cycle and stress.
Visual signalling believed to encourage long-term pair-bonding e.g. breasts always present, body shape (% body fat) and size, facial/body symmetry
Why is non-paternity relevant in society? (the nominated father is not the biological father)
Risk-taking behaviour during ovulation due to hormonal influences. Social reasons (infertility of chosen mate)
What are the influences of the menstrual cycle?
Women more forward during ovulation.
Men identify women as more attractive during ovulation.
Women selectively guard their desirable mates from ovulating women.
Men act more jealously. Testosterone will increase if they identify rivals during their mate’s ovulation period.
