Lecture 24
Ageing
− ageing – progressive physiological changes in an organism over time that result in a
decrease in intrinsic ability to survive and reproduce, and an increase in health problems
− universal but highly variable
Is ageing universal?
− Steward et. al.: the evolution of aging stems from the way our cells divide, and it starts with
symmetry
− for a population to have a good survival, it is not necessary to evolve impossibly perfect
molecular maintenance mechanisms – an immortal germline & disposable soma
− no organism lives forever, but there is a large variation in lifespans between and within
species
− there is also a large variation in age-related health problems
, Ageing & life history
− life history theory – attempts to understand how natural selection designs organisms to
achieve reproductive success, given knowledge of how selective factors in the environment
(i.e., extrinsic mortality) and factors intrinsic to the organism (i.e., trade-offs, constraints)
affect survival and reproduction
− explain inter- and intraspecific variation in the characteristics of the life cycle
(longevity, development time, age at reproduction, body size, number of offspring)
Principles of life history evolution
− intrinsic mortality – assumed to be a result of aging and to increase over age (cancer;
metabolic, cardiovascular, neurodegenerative diseases)
− extrinsic mortality – assumed to be a result of environmental hazards and be constant over
age (predation, infection, starvation, dehydration, freezing)
− high extrinsic mortality: early maturation, increased fecundity, less investment in
maintenance, shorter intrinsic lifespan
− changes in extrinsic mortality in human history:
− hominin evolution: superior social structure & defenses, and parental care
− transition from hunter-gatherer to agriculture
− industrial revolution & demographic transition
,− resource acquisition & allocation
− Y-model (De Jong & van Noordwijk, 1992)
− different strategies on how to divide limited resources in space and time
− correlated responses
− trade-offs
, Mechanisms of ageing evolution
− Selection shadow
− Haldane & Medawar, 1940s
− selection acts on (early) reproduction and its force reduces with age
− Mutation accumulation theory
− Medawar, 1952
− weak selection at increased ages insufficient to remove deleterious mutations from
the population
− late onset diseases, e.g., Huntington’s disease
Ageing
− ageing – progressive physiological changes in an organism over time that result in a
decrease in intrinsic ability to survive and reproduce, and an increase in health problems
− universal but highly variable
Is ageing universal?
− Steward et. al.: the evolution of aging stems from the way our cells divide, and it starts with
symmetry
− for a population to have a good survival, it is not necessary to evolve impossibly perfect
molecular maintenance mechanisms – an immortal germline & disposable soma
− no organism lives forever, but there is a large variation in lifespans between and within
species
− there is also a large variation in age-related health problems
, Ageing & life history
− life history theory – attempts to understand how natural selection designs organisms to
achieve reproductive success, given knowledge of how selective factors in the environment
(i.e., extrinsic mortality) and factors intrinsic to the organism (i.e., trade-offs, constraints)
affect survival and reproduction
− explain inter- and intraspecific variation in the characteristics of the life cycle
(longevity, development time, age at reproduction, body size, number of offspring)
Principles of life history evolution
− intrinsic mortality – assumed to be a result of aging and to increase over age (cancer;
metabolic, cardiovascular, neurodegenerative diseases)
− extrinsic mortality – assumed to be a result of environmental hazards and be constant over
age (predation, infection, starvation, dehydration, freezing)
− high extrinsic mortality: early maturation, increased fecundity, less investment in
maintenance, shorter intrinsic lifespan
− changes in extrinsic mortality in human history:
− hominin evolution: superior social structure & defenses, and parental care
− transition from hunter-gatherer to agriculture
− industrial revolution & demographic transition
,− resource acquisition & allocation
− Y-model (De Jong & van Noordwijk, 1992)
− different strategies on how to divide limited resources in space and time
− correlated responses
− trade-offs
, Mechanisms of ageing evolution
− Selection shadow
− Haldane & Medawar, 1940s
− selection acts on (early) reproduction and its force reduces with age
− Mutation accumulation theory
− Medawar, 1952
− weak selection at increased ages insufficient to remove deleterious mutations from
the population
− late onset diseases, e.g., Huntington’s disease
