How culture transformed human evolution

Cumulative cultural evolution

1. Essential for human super adaptation

2. Requires people to ignore “reason”

3. Leads to novel behaviors

Cumulative cultural evolution

1. Essential for human super adaptation

2. Requires people to ignore “reason”

3. Leads to novel behaviors

Apes

Lions

Wolves

60kya

30kya

50kya

40kya

Usual explanation:

We’re smarter than the average bear

These inferences are played out internally in mental models of the world, governed by intuitive conceptions of physics, biology, and psychology, including the psychology of animals. It allows humans to invent tools, traps, and weapons, to extract poisons and drugs from other animals and plants…. These cognitive stratagems are devised on the fly in endless combination suitable to the local ecology. They arise by mental design, and are deployed, tested, and fine‐tuned by feedback in the lifetimes of individuals…

Steven Pinker, “The cognitive niche”, PNAS 2010

Humans are smart…

But not nearly smart enough

Your new home

Not a ridiculous question

You need warm clothing

• What animal?

• Harvested when?

• How to cure?

• What design?

• Where to get thread?

• Needles?

• How to stitch?

You need a bow to hunt caribou

You need shelter, light and water

And much, much more

So, will you make it?

Humans learn from each other

⇒ Spreads cost of innovation over many individuals

Cumulative cultural evolution

1. Essential for human super adaptation

2. Requires people to ignore “reason”

3. Leads to novel behaviors

Imitation evolves, but no increase in adaptability

Frequency of Imitators 0 1

Fitness of Imitators

Fitness of Learners

Cost of Learning

Average Fitness at Equilibrium

Has to make individual learning more efficient

Frequency of Imitators 0 1

Average Fitness at Equilibrium

Average Fitness at Equilibrium

Fitness of Imitators

Fitness of Learners

1. Imitation allows selective learning

2. Imitation allows accumulation of small improvements

⇒ Ignore reason and copy others

Cumulative cultural evolution

1. Essential for human super adaptation

2. Requires people to ignore “reason”

3. Leads to novel behaviors

Cultural adaptation creates a tradeoff

• Benefit: low cost information.

• But, have to be credulous…

• Result: “Maladaptive” ideas can spread

Content biases spread false beliefs

Prestige biases spread maladaptive beliefs

Prestige biases spread maladaptive beliefs

Credibility enhancing displays spread costly behaviors

Rapid cultural evolution can increase variation among groups

Bell et al PNAS 2009

Sarah Mathew

Increase variation among groups ⇒ spread of group beneficial norms

Mathew and Boyd PNAS 2010

Increase variation among groups ⇒ spread of group beneficial norms

Does cultural evolution override biology?