Week 7

Question 1

Describe the Savannah hypothesis

Answer 1

The genus Homo emerged at a time of climate change and expansion of open Savannah habitats

Question 2

According to the Savannah hypothesis, traits that are considered “human” are…

Answer 2

Adaptive solutions to life in the savannah = hot and dry climates

Question 3

Define a niche

Answer 3

Every selective pressure to which a population is exposed

Question 4

Are there genes for inheritance of chronic disease?

Answer 4

Yes, but they are negligible compared to how much chronic disease is actually prevalent in society

Question 5

Are there genes for life history traits?

Answer 5

Yes, and they are substantial!

Question 6

Give examples of life history traits we know are controlled by genes (5)

Answer 6

1. birth weight
2. infant growth rate
3. pubertal timing
4. adult height
5. adult weight

Question 7

Describe a major goal of the human genome project

Answer 7

Pre 1990s, the human niche was considered to be relatively unchanging and experts thought the main selective pressures on humans would be genetic

Looked for genes which could be the basis of chronic disease!

Question 8

In the long term, climate appears to be relatively (stable/unstable), but in the short term, it is actually (stable/unstable)

Answer 8

Stable, unstable

Question 9

Describe the changing temperature of the planet over the last 60 kya

Answer 9

Rapid shifts in temperature

Question 10

What would the main selective pressure have been against hominins in a changing climate?

Answer 10

No conditions to truly adapt to; need to adapt to instability

Question 11

How did natural selection alter the human risk management system?

Answer 11

Shaped the capacity for generating risk-management systems: increased capacity for risk-management

Question 12

What is bet-hedging?

Answer 12

Adapting based on odds, not necessarily based on the environment

Question 13

What are the 2 main kinds of bet-hedging?

Answer 13

Diversifying and conservative

Question 14

Describe diversifying bet-hedging

Answer 14

Offspring will have different phenotypes in the hopes that some will be well-suited for the environment. The population doesn’t converge on one pheotype

Question 15

Describe conservative bet-hedging

Answer 15

Pick one average phenotype and stick to it. The offspring might not be the best adapted to the environment but they probably won’t be the worse either

Question 16

Describe reversibility in regards to a strategy for risk-management

Answer 16

Reduced life-course commitment to any one phenotype = phenotypic plasticity

Question 17

A periodic fast-onset warming event is called…

Answer 17

El Nino: causes severe floods

Question 18

A periodic fast-onset cooling event is called…

Answer 18

La Nina: can cause severe drought

Question 19

After El Nino periods, why does disease burden increase?

Answer 19

Stress might cause switch to faster life histories, and flooding will cause spread of disease from disease vectors such as mice or rats

Question 20

What are 2 huge drivers of ecological instability which affect human life history strategies?

Answer 20

Infectious disease and food availability

Question 21

When do homo sapiens appear in the fossil record, roughly?

Answer 21

2 million years ago, ish

Question 22

What (generally) was happening to other species 2 million years ago, and what does this reflect?

Answer 22

Shorter body size (diverted investments), flexible behaviour, specialists tend to go extinct around then = fast life history! environmental volatility

Question 23

Describe the specialist/generalist behaviour of Paranthropus

Answer 23

Specialized in what they eat - similar to gorillas now. They also die out around 2 million years ago (remember, specialists die at this time)

Question 24

El nino and la nina events are referred to as…

Answer 24

Enso cycles

Question 25

Give five examples of adaptive responses to enso cycles in more generalist species

Answer 25

1. Long lifespan: can miss a breeding season if conditions are suboptimal
2. rapid reproduction when things are good
3. Cooperative breeding (makes reproduction more viable in poor years)
4. Slow and plastic early life growth (to tolerate unexpected ecological deterioration)
5. The capacity to store energy

Question 26

Describe how sociality can be an energy store in primates

Answer 26

Social loans: lending and returning favours, social relationships - safety nets for if you fall on hard times

Question 27

Describe how cooperative breeding can be an energy store in primates

Answer 27

If you die, your genes live on through your offspring and someone else will take care of them to ensure the genes are passed on to the next generation

Question 28

Describe how the human life history strategy compares to other primates. What species is its similar to?

Answer 28

Generally different than other primates, tends to be more similar to species which are adapted to changing environments

Question 29

What 3 traits of the human life history strategy are unusual compared to other primates?

Answer 29

1. slow growth and ageing, but fast reproduction
2. high adiposity and large brain
3. sensitive insulin metabolism

Question 30

What are the 4 levels of adaptation?

Answer 30

1. environment
2. culture and technology
3. physiology and development
4. genetic adaptation

Question 31

The dogma of evolution of brain size states that in relation to life history strategy…

Answer 31

Brain size evolved first

Question 32

Why would it make sense for life history to evolve prior to our increase in brain size?

Answer 32

Big brain was a biologically favoured trait, and life history reorganization could be reorganized to provide the energy for this huge advantage, then brain size increase could have evolved

Question 33

What is happening to the climate that homo sapiens evolved in in the short term?

Answer 33

Large and frequent climatic fluctuations

Question 34

Evolution of this important trait coincides with the start of fluctuating global climate

Answer 34

Brain size: growth after the onset of these fluctuations is exponential

Question 35

In a map of genetic distance, humans are (close/different) in genome

Answer 35

Extremely close despite intense phenotypic variations!

Question 36

One (of many) possible explanations for the human phenotypic variation present in the global population is…

Answer 36

Our flexibility in life history to adapt to different environments

Question 37

What life history strategy does an organism use if the environment is constantly changing?

Answer 37

Strategy of no strategy: favour metabolic adaptability

Question 38

If glucose homeostasis is so important, why isn’t it more canalized?

Answer 38

It is the strategy to which we have adapted: metabolic adaptability - glucose/insulin is the mechanism of diverting resources to different organs

Question 39

What could be an explanation for why chronic disease doesn’t have much of a genetic basis?

Answer 39

Chronic disease is a response to plasticity in insulin metabolism - particularly when it is being overloaded

Question 40

Describe the obesogenic niche

Answer 40

Prevailing economic policies subject individuals to invasive cues favouring fat accumulation

Question 41

Genetic variability may affect susceptibility to chronic disease, but what other key element is required for a diseased phenotype?

Answer 41

The obesogenic niche - lifestyle!

Question 42

Define the factors which make up the obesogenic niche (do not list factors)

Answer 42

The total sum of modern selection pressures: diet, activity, pressure to consume, physical and social factors

Question 43

Is the obesogenic niche exclusive to humans?

Answer 43

It is possible in other animals (re: fat dogs, cattle) but it is unnatural for them due to their lack of industrialization