This knowledge is cultural

From How do people learn to cook a poisonous plant safely? by Tim Harford.

In 1860, Robert Burke and William Wills famously led the first European expedition across the largely unknown interior of Australia.

It did not go well. Due to a combination of poor leadership, bad planning and misfortune, Burke, Wills and their companion John King ran out of food on the return journey.

They became stranded at a stream called Cooper's Creek, having found no way to carry enough water to cross a stretch of desert to the nearest colonial outpost at the unpromisingly named Mount Hopeless.

"We have been unable to leave the creek," wrote Wills. "Both camels are dead and our provisions are done. We are trying to live the best way we can."

The local Yandruwandha people seemed to thrive despite the conditions that were proving so tough for Wills's party.

The Yandruwandha gave the explorers cakes made from the crushed seed pods of a clover-like fern called nardoo.

But perhaps the trio had already learned enough to survive? They found fresh nardoo and decided to make their own cakes. At first, all seemed well. The nardoo cakes satisfied their appetites, yet they felt ever weaker.

Within a week, Wills and Burke were dead. It turns out that safely preparing nardoo is a complex process.

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Nardoo, a type of fern, is packed with an enzyme called thiaminase, which is toxic to the human body. Thiaminase breaks down the body's supply of Vitamin B1, which prevents the body using the nutrients in food.

Burke, Wills and King were full, but starving.

The Yandruwandha roasted the nardoo spores, ground the flour with water, and exposed the cakes to ash, each step making the thiaminase less toxic. It is not something one learns to do by chance.

Barely alive, King threw himself on the mercy of the Yandruwandha, who kept him alive until European help arrived months later. He was the only member of the expedition who survived.

As a foodstuff, nardoo is a curiosity.

The same cannot be said of cassava roots, which are a vital source of calories in many tropical countries, particularly for subsistence farmers in Africa.

My father frequently mentioned a variant of this puzzle to me when I was a child. His examples were yeast (marginally understandable) and olives (much less so). How do you explain an outcome whose predicate steps seem non-value adding.

Harford is using these examples to introduce the work of Joseph Henrich in The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter an excellent read.

But how does anyone learn the elaborate preparation needed for cassava or nardoo?

No single person does, according to Joseph Henrich, an evolutionary biologist.

He argues this knowledge is cultural. Our cultures evolve though a process of trial and error analogous to evolution in biological species. Like biological evolution, cultural evolution can - given enough time - produce impressively sophisticated results.

Somebody stumbles on one step that seems to make cassava less risky; that spreads and another step is discovered. Over time, complex rituals can evolve, each slightly more effective than the last.

A good summary of an interesting hypothesis with huge implications.

Combine the cultural learning ideas of Henrich and the affiliative network ideas of Nicholas Christakis (Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives -- How Your Friends' Friends' Friends Affect Everything You Feel, Think, and Do) and you end up with some quite intriguing, likely true, implications which are dramatically at odds with the received wisdom of the Mandarin Class.