Chap 3: Combating the hostile forces of nature (Human survival problems)

What are survival problems?

Cases where more individuals are produced than can possibly survive

What does survival mean?

Dealing with various struggles

What are the 3 different categories of struggles humans and animals undergo?

1. Tough physical conditions

2. Individuals of the same species

3. Individuals of different species (predators, competitors, parasites, toxins)

What is the problem animals and humans face with food selection?

They need calories and nutrients, but many things are not edible or worse, poisonous eg. plants

For plants, how does having only its fleshy parts non-poisonous help with its reproductive potential?

Animals or birds will only eat the fleshy parts, which contain the seeds, and help to disperse it faraway

Food selection in Rats (no definition)

What kinds of foods do rats prefer & avoid?

Depending on current physical needs, they prefer water, and sweet or salty foods, and avoid bitter

What kind of fear do rats develop and how does that relate to them trying small, separate samples of new food?

Neophobia (intense fear to anything new) due to a evolutionary history of being poisoned → have to be picky about trying new foods and try in small, separate amounts to be cautious and identify what exactly caused their sickness

Food selection in humans (no definition)

How do we avoid ingesting toxins? (4 reactions)

1. Disgust reactions

2. Spitting

3. Gagging

4. Vomitting

Based on studies on Americans and Japanese, what are the greatest sources of parasites and toxins?

Feces and body waste

Why do women get pregnancy sickness in their 1st trimester?

To avoid teratogens found in meat & veg in the timeframe where infants develop organs and are most sensitive to toxins

What circumstance do women who do NOT get pregnancy sickness in the 1st trimester get into?

3x more likely to spontaneously abort

What is the Antimicrobial Hypothesis?

Spices kill bacteria

How did this hypothesis form?

Likely through trial and error + cultural transmission (rather than evolution)

What is the frugivory byproduct hypothesis?

Our attraction/taste for alcohol is a byproduct of our ancestor’s preference for ethanol present in ripe fruit

What are the two hypotheses for human food procurement?

1. The hunting hypothesis: Male provisioning

2. The gathering hypothesis: Female provisioning

What are the evidences supporting the hunting hypothesis shaping human evolution?

1. Meat:

• provided essential nutrients (eg. Vitamin A & B12)

• formed a substantial part of early diets

• supported by dental evidence, enlarged small intestines adapted for protein digestion, stone tools, and cut-marked animal bones

2. Sexual division of labour evident in modern hunter-gatherers (men hunt, women gather)

What can men transporting meat account for?

Heavy male parental investment in children

What can men hunting account for?

Strong male coalitions

What can meat sharing account for?

Strong reciprocal exchange

What is the “show off” hypothesis?

Successful and better hunters gained more number and more desirable mates → higher offspring survival

What are the evidences supporting the gathering hypothesis shaping human evolution?

1. Women’s plant gathering provided the majority of calories in traditional societies

2. Emergence of early stone tools to increase foraging efficiency (later adapted for hunting)

Which hypothesis do evidence favour more?

Hunting hypothesis, but BOTH genders did play a part in food procurement

Gender differences in spatial abilities

• Women: better at spatial location memory (well-suited for foraging)

• Men: better at mental rotation of objects and navigation (well-suited for travelling longer distances for prey)

What does the Savanna Hypothesis posit?

People tend to prefer natural environments (our ancestral home) over man-made ones

What are the two elements that natural environments offered optimal conditions for?

1. Prospect (resources)

2. Refuge (safety)

What is a real life example of the Savanna Hypothesis?

People recover faster from hospital stays if they can see trees from their window (because we historically process natural scenery to be safe, peaceful, and healing)

What are 6 common human fears? (SSHSSD)

• Snakes

• Spiders

• Heights

• Separation anxiety

• Strangers

• Darkness

What are some items that are most dangerous in the modern world but less commonly feared?

• Cars

• Guns

• Electrical outlets

• Stoves

(because these items did not exist in the ancestral period)

What are 6 adaptive responses to fear and anxiety? (FFFSFF)

1. Freeze

2. Flee

3. Fight

4. Submit

5. Fright (playing dead)

6. Faint

When does the developmental timing of onset of fear coincide with?

When we face the adaptive problem

What are 4 examples of time-frames of when certain fear develops?

1. Heights, strangers (especially male): 6 months old

2. Separation anxiety: 9-13 months

3. Animal fears: 2 y/o

4. Crowded public spaces: later in life as child wanders

3 theories to explain how we combat predators

1. Ohman et al. (2001)

2. Neuhoff (2001)

3. Evolved navigation theory and the descent illusion

What is the Ohman et al. (2001) theory regarding emotions & attention?

People detect fear-relevant objects (eg. spiders, snakes) from arrays of nonfear objects (eg. mushrooms, flowers) much faster than VV

What is the Neuhoff (2001) theory regarding an auditory perception bias?

People pay more attention to approaching sounds than receding sounds of the same magnitude

What is the evolved navigation theory and the descent illusion?

Distances look greater from up above than down below

(Why? - risk seems greater from the top)

Based on Darwinian (evolutionary) medicine, why do we get sick?

To combat disease: fever and iron-sequestration to starve bacterial infections

What does a fever do?

Raises body temperature to kill disease

Why does aspirin impede recovery?

It undermines the disease-killing process, and prolongs the illness

What does iron sequestration do?

Reduces levels of iron during infections to prevent bacteria living on iron

What are the 6 costs/consequences of deaths (for a selected sample) (LLECCC)

1. Loss of access to mate’s residual reproductive value

2. Loss of additional mating opportunities

3. Eliminates all future reproduction

4. Cannot invest in children and kin

5. Cannot protect children from exploitation

6. Cannot influence or arrange kids’ mating

What is the theory supporting that humans are NOT programmed to die?

The theory of senescence; ageing is the gradual deterioration of body mechanisms

How does this link to natural selection to possibly explain why we eventually age and die?

Humans have pleiotropic genes that bring benefits of survival and reproduction in our early survival days at the expense of bringing costs (related to death) later

Which gender (& age) does suicide occur more often in?

Men, especially in early adulthood (18-35) and in old age (70+)

For young men, what are 5 things that suicide ideation/thoughts correlate with? (de Catanzara, 1995) (BNNHH)

1. Burden to family

2. Not having sex in the last month

3. Not having sex ever

4. Having unsuccessful heterosexual relations

5. Having fewer no. of children

For young women, what are 3 things that suicide ideation/thoughts correlate with? (BNL)

1. Burden to family

2. Not having sex ever

3. Lack of contribution to family

For older adults, what 5 things is suicide ideation related to? (HFBLH)

1. Health

2. Future financial problems

3. Burden to family

4. Loneliness

5. Homosexuality (men specifically)

How to explain suicide as an adaptation based on kin selection?

It can re-channel resources from a non-reproductive individual to reproductively viable relatives

What is the Byproduct Hypothesis (Saad, 2007) regarding suicide?

Suicide occurs as an occasional spillover in response to extreme sex-linked “defeats” in evolutionary relevant domains, which adaptively trigger depression and sadness that might spiral out of control

What are the primary categories of sex-linked defeats for each gender?

• Males: jobs, status, wealth

• Females: PA