Primate Energetics

Question 1

When did homo sapiens arise?

Answer 1

300 kya

Question 2

When did agriculture arise?

Answer 2

10 kya

Question 3

What percentage of human history have we likely lived as hunter-gatherers?

Answer 3

95%

Question 4

What is the ladder of progress?

Answer 4

Historical evolutionary models which depicted life as striving towards complexity, in which humans are the most complex/sophisticated

Question 5

What was the historical view on hunter-gatherer societies?

Answer 5

1) They served as a bridge between animals and modern humans
2) They were animalistic and on the edge of starvation

Question 6

Why was the historical view on hunter-gatherer societies wrong?

Answer 6

Hunter-gatherers were not struggling nor at the edge of starvation, rather they were very good at adapting to ecological challenges (doing so through cooperation)

Question 7

How did views on hunter-gatherers change?

Answer 7

In the 1950s-60s, views changed with the release of “Original Affluent Society” by Marshall Sahlins

Question 8

Who wrote the “Original Affluent Society”?

Answer 8

Marshall Sahlins

Question 9

What did Marshall Sahlins claim in his work about hunter-gatherers?

Answer 9

Sahlins claimed that hunter-gatherers had an optimal lifestyle because they did not have many needs/wants, and therefore were easily satisfied

Question 10

What evidence did Marshall Sahlins use to back up his claim of hunter-gatherers living an optimal life?

Answer 10

The data of Richard Lee, who studied Kung hunter-gatherers from Southern Africa

Question 11

What did Richard Lee find about the Kung in Kalahari?

Answer 11

Conducted a time analysis and determined that the hunter-gatherer society only spend 15 hours foraging for food per week, indicating that they were not on the edge of starvation, nor did they struggle to survive

Question 12

Why was Richard Lee’s data on hunter-gatherer work weeks inaccurate?

Answer 12

1) He did not account for time spent processing foods (to make them edible)
2) If he did, we would find that the average time spent working per week was 40-45 hours

Question 13

What did John Maynard Keynes believe would happen by 2030?

Answer 13

He believed that due to advancing technology, humans would only be required to work 15 hours per week

Question 14

What is the economic problem?

Answer 14

The struggle for subsistence, which is a problem for all of the biological kingdom

Question 15

What did researchers find upon investigating time budgets of animals?

Answer 15

A large proportion of their active time is spent in inactivity

Question 16

Why might animals exhibit laziness?

Answer 16

If an organism’s goal is to stay alive, one satisfactory strategy is to only initiate foraging when hungry, and rest once satisfied

Question 17

What is unique about the “laziness” perceived in bees?

Answer 17

There are always a designated group of bees that do nothing in case other workers get lost or need help

Question 18

What is one reason that primates have slow life histories?

Answer 18

Primates have lower TEE than non-primate animals (exhibit metabolic deceleration)

Question 19

What is TEE?

Answer 19

Total Energy Expenditure (number of calories burned per day)

Question 20

How is TEE measured?

Answer 20

Animals are given isotopically tagged water, in which the rate of decay can be measured in their urine

Question 21

What is “breaking through the grey ceiling”

Answer 21

Humans seem to have solved the energetic problem, where they have higher reproductive output, larger brains, and more exceptional longevity compared to other primates (no evidence of tradeoffs)

Question 22

How did humans “break through the grey ceiling”

Answer 22

Relative to other primates, humans have accelerated their metabolism

Question 23

How was metabolic acceleration achieved in humans?

Answer 23

Through shifts in foraging behaviour (that is, shift toward higher quality, large package sized foods that were harder to gain)

Question 24

Compare and contrast the foraging behaviour of chimpanzees/NHM and humans?

Answer 24

1) Other primates tend to eat food with low-nutrients but are more easily accessible, rarely spending more energy to go for bigger game
2) Humans tend to go for “large game” that is nutritionally dense but extremely difficult to obtain, rarely opting for lower-nutritional foods

Question 25

What is the consequence of opting for large, high-variance food packages?

Answer 25

Since these foods are rare, humans have to travel further = more energy expenditure

Question 26

What was the most likely selective pressure that resulted in the evolution of bipedalism?

Answer 26

Increased day range that came with shifts toward foods that were harder to gain

Question 27

What most likely led to increased cooperation and division of labour in human behaviour?

Answer 27

1) Since foods we obtained were large, we would share food
2) Since foods were harder to gain, cooperation was beneficial in that it increases chances of success

Question 28

Compared to other primates, do humans develop quicker or longer?

Answer 28

Longer

Question 29

Compared to other primates, do humans gain more energy or less energy?

Answer 29

Humans produce large surpluses as adults (high adult productivity and provisioning)

Question 30

Comparing humans and other primates, who works for a longer period of time?

Answer 30

1) Humans work less hours per day compared to other great apes
2) From an efficiency standpoint, we are no more efficient than great apes but time-wise we are

Question 31

How does spending less hours working (towards subsistence) relate to energy input?

Answer 31

1) Humans work less hours but spend more energy while working
2) Humans spent ~15-20% of their energy gathering food per day

Question 32

What is the benefit to working hard for a shorter period of time?

Answer 32

Return rate (calories coming in per unit time) is much higher than in other apes

Question 33

What is the consequence for working so hard in humans?

Answer 33

We must rest a lot more

Question 34

What is locomotor economy?

Answer 34

Efficiency in moving (energy expended per unit of distance)

Question 35

How do distances travelled by hunter-gatherers and chimpanzees compare?

Answer 35

1) Chimpanzees move ~4-5 km per day
2) Hunter-gatherers move ~10-15 km per day

Question 36

What do patterns of locomotor economy look like between humans and chimpanzees?

Answer 36

1) Humans have U-shaped walking efficiency (cost of transport as a function of speed), where there is an optimal walking pace that minimizes cost of transport
2) Chimpanzees have a straight-line walking efficiency (the cost of transport continues to increase with speed), and traveling at any speed is much more costly than humans

Question 37

Why are humans so efficient at walking?

Answer 37

Due to bipedalism, humans require fewer muscle activations when walking compared to chimpanzees

Question 38

Comparing humans and chimpanzees, which one is stronger?

Answer 38

Chimpanzees are 1.5-2x stronger than humans

Question 39

Why are chimpanzees stronger than humans?

Answer 39

1) They have same properties of muscle but chimpanzees have longer muscle fiber
2) Chimpanzees possess 2x more fast-twitch muscle fiber (suited for rapid movement)
3) Humans possess more slow-twitch muscle fiber (contract more slowly)

Question 40

What are chimpanzee muscles more suited for?

Answer 40

Rapid movement

Question 41

What are human muscles more suited for?

Answer 41

Endurance