o Flashcards
What does iteroparous mean?
It refers to species that have more than one reproductive episode in their lifetime.
What is senescence?
Senescence is biological aging, often accelerated by the energetic costs of reproduction.
What is reproductive senescence?
The age-related decline in fertility; in most mammals, it occurs near death, but in humans it ends in memnopause.
At what age does human female fertility begin to decline?
Around age 32, with a steeper decline after age 37.
What is permimenopause?
The transitional period of declining fertility leading up to menopause, typically between ages 40-50.
What is menopause?
The final menstrual period; typically occurs around age 51 (range: 40-61). Ovulation usually ends before this.
What is post-menopause?
The period after menopause, often lasting from age 50-80+, during which a woman is no longer fertile.
Is age at menopause heritable?
Yes, daughters tend to reach menopause at a similar age as their mothers.
What does Modern Medicine Hypothesis propose?
Menopause is a byproduct of modern medicine extending lifespan beyond reproductive capacity.
What supports this hypothesis? (Modern Medicine Hypothesis)
Chimpanzees rarely live past 50, and menopause happens around that age in humans.
What challenges this hypothesis? (Modern Medicine Hypothesis)
Evidence shows pre-modern humans often lived into their 60s or 70s if they survived childhood.
What has modern medicine impacted the most regarding lifespan?
Significantly reduced childhood mortality.
What does the Mate Choice Hypothesis propose?
Men prefer younger wives, creating selective pressure for menopause.
What is wrong with this logic? (Mate Choice Hypothesis)
It assumes stopping reproduction increases fitness, when looking younger would be more beneficial.
What is the grandmother hypothesis?
Post-reproductive women gain more fitness by helping their descendants survive and reproduce, increasing inclusive fitness.
What is inclusive fitness?
Genetic success achieved through one’s reproduction and that of closely related kin.
What is Kin selection?
The evolution of behaviours that increase the reproductive success of close relatives.
Which species show string support for the Grandmother Hypothesis?
Resident Killer whales.
How do ocas exhibit post-fertile contribution?
Post-reproductive females lead pods during salmon shortages, improving group survival.
What did Brent et al. (2015) find?
Post-fertile female orcas increased leadership during salmon scarcity, using ecological knowledge.
What did Nattrass et al. (2019) find in orcas?
The death of post-fertile grandmothers decreased the survival of young orcas more than reproductive grandmothers.
What evidence supports this in elephants? (Nattress)
Calves of young elephant mothers had 8x lower mortality when their grandmother was present (Lahdenpera et al., 2016).
What other effect did elephant grandmother have?
They shortened the inter-birth interval of their daughters.
If the Grandmother hypothesis is valid, why don’t more long-lived mammals have menopause?
Possibly due to difficulty studying other species like narwhals, belugas, and pilot whales.
