Humans’ Amazing Evolution From Hunter-Gatherer to Safeway Shopper

Ruth DeFries, chair of the department of ecology, evolution, and environmental biology at Columbia University, in New York, and author of The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis, has spent much of her life looking down at Earth from a great height, using satellite images to track human development. But to understand how we went from being hunter-gatherers to a species that so completely dominates the planet, she had to go much further back in time.

Speaking from her home in New York, she guides us from the rain forest of Brazil to the latest developments in foods containing genetically modified organisms (GMOs). On the way she explains why food is at the heart of human civilization, what we need to do to feed the world in the coming decades, and why it's not just the quantity of the food we produce that matters, but also the quality.

My dictionary says a ratchet is either a tool or rap slang for a diva. What's the "Big Ratchet"?

A ratchet is a colloquial urban term, as you suggest. But it's also a mechanical tool. You turn the ratchet in one direction, and you can't go back. The ratchets in the book refer to the ways people have figured out how to manipulate nature to produce food.

Once we have these technologies, we produce more food, ratchet up the population, and that continues on. The Big Ratchet refers to the past 50 years, when we've had an explosive increase in food production. The amount of food produced has surpassed even the explosive growth in population.

So the story of the Big Ratchet is how we got to this point. How we figured out, through genetics, nutrients, irrigation, and pesticides, to lift the constraints that nature placed upon us.

You start your story in the Brazilian rain forest with the Kayapo Indians. Tell us how they feature in modern-day food production and why their story is part of our own evolutionary history.

I was doing work in the Brazilian rain forest using satellite data to track deforestation. That took me down to the ground to a very interesting part of the world, the state of Mato Grosso, in Brazil. At the time, in the early 2000s, it had the highest rate of deforestation in the world. Within that landscape there was a reserve for the Kayapo Indians, who were still living as hunter-gatherers.

So there was this amazing juxtaposition with modern agriculturegiant tractors, planes flying pesticides, everything you think of with modern agriculture for the cultivation of soy and other crops.

But before we started to domesticate plants and animals around ten or twelve thousand years ago, everyone lived like the Kayapo. Everyone hunted for wild animals, foraged for seeds and berries and fruits. That was the way we interacted with nature to get food.

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Humans' Amazing Evolution From Hunter-Gatherer to Safeway Shopper