evolution of ageing Flashcards
are we living longer
in 1990, less than 17 million people in the world were older than 65 (less than 1%), in 2020 it was ~9.5%
by 2050, predicted 2.5billion people 65 years or older
less babies being born
growing old is an ancient human characteristic
growing old
is an ancient human characteristic
average age at death is the least likley age to die- will be spread around the average
archeology samples show that 100,000s of years ago individuals lived to age 54-68yrs
comparative biology
how ageing and longevity varies between species
late acting deleterious mutations
huntingtons- genetic, neurodegenerative disease caused by highly penetrant dominant mutation
average age of onset is 35.5 years
so many women have already reproduced before the disease is seen so genes are passed on unknowingly
hence why natural selection hasnt acted to remove the mutation
mutation accumalation theory
even in a population free of ageing, death will occur from extrinsic hazrds such as deisease, predators and ageing
theory that the force of natural selection reduced with age as indiviuals have less chance of producing offspring
early acting mutation- most bearers are still alive, strong forces of natural selection
late acting mutation- few bearers still alive, weak force of natural selection
antagonist pleitropy theory
supposes there are mutations beneficial in youth but at the price of higher rate of ageing- bad effects later in life
more individuals will survive to express the early benefit than will survuve to suffer the higher rate of ageing
mutations like this can be incorporated by natural selection
ageing evolves, is programmes as a side effect of natural selection in favour of mutations that cause a benefit during youth
disposable soma theory
ageing is a result of natural degrading processs that result in accumlation of damage but the damage can be repaired by the organism at the expense of reproductive effort
organisms only have a limited amount of energy that has to be divided between reproductive activities and the maintenence of the non-reproductive aspects of the organisms
due to declining evolutionary impact of the adverse events on older animals, a trade off exists which it does not make sense for an organism to invest effort in maintenance to result in living much beyond initial breeding years
grandmother hypothesis
post menopausal longevity evolved in human ancestors when grandmother played a key role in providing for youngsters when the mother of those youngsters bore their next baby
reserve capacity hypothesis
selection for prolonged growth and greater RC allow for evolution of lower adult mortality and greater longevity in human beings
childhood and adolescence evolve to
- enhance fertility of mothers
- improve survival of mothers
- help the young to develop resilient phenotypes that reduce the risk of mortality in the young and adults
life history theory
studies the allocation of limited resources (eg energy + time) to growth, maturation, productivity, reproduction
LHT- trade offa
growth vs reproducion
live fast die young vs live slow die old
evolution of menopause
human women have both a decline in age specific reproductive rate and a complete cessation of ovulation
multilevel selection
level 1- childhood frees mother to reproduce again more quickly and with lower mortality risk than any other primate
level 2- evolution of childhood prolongs offsprint dependency
leads to trade off- evolution of bioculatural reproduction
3- slower growth and more RC- greater adult health, fitness and longevity
trade off- lost early life reproduction but greater fitness for mother and offspring
4- once life expectancy passes 45-50yrs, postreproductive life stafe of significant duration and menopause become commonplace
trade off- biocultural roles for grandmothers
