Guns, Germs, and Steel: Chapter 7 Summary & Analysis

Nature is full of inedible and even poisonous foods. And yet all edible crops arose from wild species that humans learned to domesticate. Who came up with the idea to domesticate a crop?

To begin with, there are thousands of living creatures that “domesticate” plants, of which humans are one. Animals eat plants and defecate the seeds, often traveling thousands of miles before doing so. Thus, animals select the kinds of plants they want to eat (by eating them), spread them to other places (by walking or flying) and then plant them in the earth again (by defecating). Indeed, most plants have evolved to the point where they can survive being digested by most animals.

The earliest farmers didn’t understand genetics. But they did know that seeds could be planted to produce new crops, and they knew that if they planted the seeds of crops that they particularly liked, those seeds would grow into crops that shared their “parents’” useful qualities.

The almond is a great example of how plants have become domesticated over the centuries. Wild almonds are bitter and even poisonous—some of them contain cyanide. But some almonds have a mutation that makes them non-bitter. Eventually, humans would have discovered the non-bitter almonds. The seeds of those particular almonds must have been harvested and replanted, resulting in a new generation of non-bitter almonds. Much the same is true of thousands of foods: strawberries, mustard, poppies, lentils, etc.

The agricultural revolution began in the Fertile Crescent of Mesopotamia, when humans noticed that certain seeds, such as barley, did not “pop” out of their protective stalks. Previously, mutant seeds that didn’t emerge from their stalks were biologically useless; they just disintegrated. But humans used these otherwise useless seeds to plant crops and create a new generation of barley crops. Over millennia, humans’ preference for mutant grains that grew quickly and could be harvested easily resulted in domesticated barley and wheat that were very unlike wild barley and wheat.

Other crops, such as bananas, oranges, and grapes, developed reproductive mutations that allowed them to self-fertilize; i.e., bear fruit without interbreeding with another plant. The grapes and bananas that humans consume today are hermaphroditic and self-reproducing. But thousands of years ago, they were just mutants, selected by early farmers because they were convenient to grow and breed. Early farmers didn’t understand biology or genetics, but they knew what was most convenient to farm; a cherry tree that bore fruit without any pollination was easier for a farmer to care for.

Many of the crops that humans grow and eat have evolved to the point where they bear little to no resemblance to their wild counterparts. Some plants were domesticated earlier than others, and some plants still haven’t been domesticated, even though humans have been trying for a long time. The original domesticated crops were wheat and barley, probably because they were fast-growing, easy to harvest, and self-pollinating. Later, humans learned to domesticate figs and olives—crops that grew more slowly. Then, humans learned to domesticate fruit trees, which can only be domesticated with grafting. In short, humans learned to domesticate different plants at different times: by and large, and across civilizations, humans learned to domesticate fast-growing, easy-to-harvest crops first, and slow-growing crops later on (if at all). By the time of the ancient Romans, most of the world’s leading crops were being cultivated somewhere in the world.

Some plants we never figured out how to domesticate. Consider acorns, the seeds that produce oak trees. Acorns are highly nutritious, but they’re also too bitter for most people to enjoy. Acorns were never domesticated because 1) they’re slow-growing, 2) squirrels eat too many acorns, and 3) it’s hard to “breed out” bitterness in an acorn. With a crop like an almond, on the other hand, a single gene (that can be bred out quickly) controls bitterness.

The most obvious example of evolution is the food we eat today. Over centuries, crops have evolved, with humanity’s guiding hand, to be sweeter, bigger, and faster growing. Even Charles Darwin begins On the Origin of Species by discussing how farmers have cultivated gooseberries over the centuries.