How Did Cultural Evolution Let Humans Beat Smarter Species?

Transcript

Today, I have the pleasure of chatting with  Joseph Henrich, who is a professor of human   evolutionary biology at Harvard University  and an author of two of my favorite books, The Weirdest People in the World and before  that, The Secret of Our Success. And I was just mentioning to you that I remember reading  this many many years ago when I was ... Read More

Key Insights

• Genetic changes do not obviously explain the expansion out of the Near East 70,000 years ago, because David Reich's lab has found no clearly big DNA changes, and Neanderthals had larger brains that usually go with stronger problem solving.
• Human history is a story of repeated population expansions, including the Bantu expansion about 5,000 years ago, the Austronesian peopling of the Pacific, and the Neolithic expansion into Europe, each at the expense of other groups.
• Institutions that interconnect a population can help maintain more sophisticated technology, so social organization may matter as much as any single invention in explaining why one group spreads.
• Technologies are gained and lost over time: Australia never invented bows and arrows, and the New World probably lacked them before later developing them, which shows that knowledge is not guaranteed to accumulate.
• The collective brain explains why nearly every big first invention appeared in Eurasia, the largest continent with the biggest population and an east-west axis that lets ideas and people flow more easily.
• Ian Morris's Lucky Latitudes, a belt from southern China to the Mediterranean, kept ideas moving back and forth, and the same flow supported more complex state bureaucracies.
• Expansions succeed through a package of practices rather than one technology: the Inuit combined social ties, bows and arrows, dogs and sleds, and boats for whaling to out-compete and eventually exterminate the Dorset.
• The Dorset probably had better technology but spread out, saw their languages diversify, lost contact, and began losing technology, so history is a pulse of expansions and collapses, not one long march to victory.

Questions & Answers

Q: What happened to humans in Eurasia 70,000 years ago?

Genetic evidence from David Reich's lab suggests that a small group, possibly 1 to 10,000 people in the Near East, expanded and became the ancestor of everyone descended from Eurasia, replacing or absorbing other human species. Henrich says the exact cause is unknown, but it likely involved cultural packages such as tools and social organization.

Q: Did genetic changes cause modern humans to out-compete Neanderthals?

Henrich says there are no obviously big changes in the DNA found by Reich's lab. Neanderthals had larger brains, and in primates larger brains usually go with more computational ability, so the expanding group may have been less able to process information individually. That points toward culture and institutions rather than raw biology.

Q: Why were there no wheels in the New World?

Henrich's explanation is the collective brain. Almost every big first invention was made in Eurasia, which is the largest continent, has the biggest population, and has an east-west axis along which ideas and people flow. The New World did have wheels on Mayan toys, and dogs and llamas could pull carts.

Q: What is the collective brain?

The collective brain is the idea that innovation comes from many interconnected people experimenting and sharing, not from individual intelligence. Larger and better-connected populations accumulate more pieces of knowledge. Henrich uses it to explain why Eurasia produced so many first inventions and even why more complex state bureaucracies developed there.

Q: How did the Inuit expansion replace the Dorset people?

The Inuit expanded from the north slope of Alaska across the Arctic to Greenland with a package of social practices that kept them interconnected. They also had bows and arrows, dogs and sleds, and boats for whaling. The Dorset lacked bows and arrows, and they had spread out, lost contact, and lost technology.

Q: Why do populations lose technology and fragment over time?

Henrich describes a cultural evolutionary dynamic: languages naturally diversify, which reduces contact. People may then marry within their own group, and neighboring groups seem more culturally different, like outsiders. Geography and local learning pull populations apart, so staying unified is the tough part humans have always faced.

Q: How can institutions help a group expand?

Institutions that interconnect a population can maintain more sophisticated technology. In Australia, an expansion about 6,000 years ago took up seven-eighths of the continent with new rules about marriage, linguistic exogamy, and rituals that gathered communities for months, which gave plenty of time for exchange and teaching.

Q: How do groups compete when expanding populations meet?

Groups can copy each other, for example by adopting good tools or taking in migrants who bring practices. There is also plenty of evidence of violent conflict, and ancient DNA shows dead-end genetic lineages. Neanderthals are a dead end in a sense, though humans interbred with them and carry some of their DNA.

Summary & Key Takeaways

• The conversation starts with a puzzle from ancient DNA: around 70,000 years ago a small group in the Near East expanded and became the ancestor of everyone descended from Eurasia. Henrich says genes do not clearly explain it, and that larger-brained Neanderthals were probably better at individual information processing.

• Henrich points to recent history, where expansions like the Bantu, Austronesian and Neolithic ones replaced other populations. He suggests institutions that connect groups, plus tools such as bows and arrows, let expanding populations maintain complex technology. Groups can also copy each other, but violent conflict and dead-end lineages are well documented.

• Expansions come as packages of technology and social organization, as with the Inuit and the Australian expansion that began about 6,000 years ago. Such packages decay when languages diversify and contact is lost, because geography and local learning fragment populations. Staying unified is the hard part, which is why Henrich frames history as cycles of expansion and collapse.