BIO 115

food availability unpredictable -> not possible to sustain large population size -> if humans still HG earth's population is maximized at 100 million people

1) small bands with high mobility and no possessions

2) Group structure -> social systems and networks

1) Variety of tools

2) Cooperation and equality

-> allowed humans to produce more energy and have increased reproduction

- very fast expansions

- populations increased in numbers

- diet change

- Agricultural diets are much poorer -> dental caries, abscesses, tooth decay, anemia and iron deficiency

- Sedentism and animal domestication -> less moving -> impaired physical fitness and the spread of diseases of domesticated animals

+: 16.7% higher fertility rate than mobile; 20.5% increase in age-controlled fertility; 15.8% increase in reproductive fitness; additional 0.59 offspring

-: 63.2% increase in mortality rates; 36.16% increase in polyparasitic infections; more viral diseases

Quantity and predictability of food supply instead of quality.

1) Increased carrying capacity -> higher populations

2) Starch and baby food -> helps increasing female fertility

3) Storage -> prerequisite for the development of complex technology

4) Long term immunity -> smallpox, tuberculosis

Because of the increased fertility rate the population was able expand in spite of high mortality.

Humans are the only ape that have male-female labor division

Sex equality disappears with farming

1) humans became good at fighting diseases

2) good at fighting perinatal diseases

3) good at fighting parasites

-> hygiene, vaccinations, development of medicine, more food variety

It is the change from agriculture whre high fertiltiy and high mortality was present to modernity where low fertility and low mortality is present. (Mortality however was first reduced)

New mismatches: diseaes not found in Hunter-Gatherers such as Alzheimer's, depression, coronary heart disease, diabetes, high blood pressure which are NOT natural consequences of getting old but consequences of drastic changes in the environment

HG evolved to crave energy rich foods -> now sugar is available in abundance and we still crave sugar -> diabetes etc.

That humans are genetically adapted to the hunter and gathering way of life but the environment has changed and evolution acts too slowly upon us.

It is associated with extended longevity in animal models.

1.9, 2.0, 1.5-1.6

over 15% reduction in physical activity today compared to earlier

Osteporosis due to reduced activity levels -> rare or unknown among hunter gatherers and farmers

Cardivascular diseases -> due to reduced activity levels -> recommendation of atleast 150 min of exercise a week

Hunter Gatherers

- Bipedal, slightly fat, furless, big-brained, tool-using, eat high fiber low carb diet and be physically active

1) What is present in all groups and therefore a human unique trait

2) What is variable in human populations -> adaptions to ecological pressures

Process of declining in fertility and survivorship rates with age.

Because ageing seriously reduces individual fitness.

Genetically yes. Event negative ageing could be possible.

Weismann 1891

- For the benefit of the species the drained are replaced by enw ones -> based on altruism

Evidence for that theory: telomeres are essential part of human cells that deplete over time by mitosis -> genes affect ageing clock

Based on that theory: ageing and death are adaptive

Example: Lemming mass suicide (Walt Disney Documentary)

1) Assumes ageing happens a priori -> cannot be an explanation for ageing

2) Can group benefits individual benefits in biology?

3) No  theoretical reason to explain why ageing would be programmed

Ageing is caused by the accumulation of irreparable damages to cells and tissues

- Organsims keep genetic repair at maximum -> when damage overcomes repair rate -> ageing

- animals with higher metabolism live longer

- caloric restriction -> reduces metabolic rates -> less oxidative stress and slower ageing -> supports rate of living theory

1) Austad and Fisher (1991) tested amount of energy expended per gram per lifetime -> ageing is not a direct by-product of metabolic rate because animals with higher metabolic rate for the same size would have aged faster

 Expect that animals of same size and close taxa to have same lifspan -> not true

2) If repairing damages is key factor -> selection for extended lifespan would not be possible -> not true, longevity can be selected for (inherited)

- ageing caused by accumulation of somatic damage

- focus on evolution of cell maintenance

- trade-offs between soma and reproduction

-> somatic maintenance needs only to be as good as their chance of survival in the wild

- ageing because we die compared to the other theories where -> we die because we age

- death is an external factor that cannot be completely controlled for by the organism -> time is the most important limitation

Assumptions:

1. Time is a limited ressource

Because accidental death cannot be controlled for (external factor)

The higher the extrinsic mortality the faster the animal's life history

Animal living in high mortality environments -> high rates of predators or accidents -> have shorter life spans -> invest in having more offspring earlier in life

Death is inevitable -> average lifespan is consequence of the ecological mortality rates -> the power of removing deleterious mutations decreases as the chances of accidental death increases