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Lecture 6

ANTB22H3 Lecture Notes - Lecture 6: Senescence, Menopause, Mate Choice


Department
Anthropology
Course Code
ANTB22H3
Professor
Joyce Parga
Lecture
6

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Lecture 6 Feb.17.11 BLUE FONT
SLIDE REPRODUCTION:
Mating Success: # of copulations achieved
Reproductive Success: #of viable (living) offspring produced
SLIDE REPRODUCTION 2:
Mating success is not necessarily equal to reproductive success
SLIDE SEX DIFFERENCES:
Females are limited by food availability
Males are limited by access to fertile females
SLIDE SEX DIFFERENCES2:
Females undergo gestation, lactation, infant care
Males often perform little to no infant care
Males can have many more babies across their lifetime than can the average male
SLIDE SEX DIFFERENCES 3:
Some males will have many offspring, others will have none (there can be high male
reproductive skew)
Certain males have lots of offspring, while some have none
The variability from one male to another can be huge amongst males with
reproductive success
SLIDE REPRODUCTIVE SENESCENCE:
Senescence: means aging, your fertility is liking to decline in old age
Males: decreased sperm counts over time
Females: eggs age; decreased fertility rates. Decreased survival of infants born to
aged mothers
SLIDE REPRODUCTIVE SENESCENCE 2:
Menopause: permanent cessation of menstrual cycles
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oMight be adaptive (via the grandmother hypothesis). If something
is adaptive it will help the animal have increased reproductive
success as opposed to other animals
oGRANDMOTHER HYPOTHESIS: older females may gain greater
fitness benefits by helping raise a daughters offspring (as opposed
to reproducing again themselves).
SLIDE REPRODUCTIVE SENENSCENCE 3:
Only VERY old females of some species (e.g. chimps) cease ovarian cycling
Researchers disagree on whether this is true menopause may just be a by-product
of aging!
BE ABLE TO EXPLAIN THE GRANDMOTHER HYPOTHESIS
KNOW THE DISAGREEMENTS
KNOW THE EFFECTS OF MALES AND FEMALES
SLIDE INTRA-SEXUAL SELECTION:
Male-male competition (or female-female competition) over mates
Traits that might be selected for as an advantage
Hamadryas baboon males: one male units
Large male body size has been selected for
Directional selection for larger canines, body size VIA intra-sexual selection
SLIDE INTER-SEXUAL SELECTION:
Mate choice (epigamic selection)
oFemales are most often the focus of mate choice studies, because they have
greater parental investment than males (ie. Orang-utans)
SLIDE SEXUAL COERCION:
Definition: the show (or threat) of force that makes a female more likely to mate with
a male when she is fertile, but at some cost to the female
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