First Farmers










The various ears of corn illustrate the genetic diversity of corn.
















Moo to you, too! Domestication changed cows, making them more docile and less threatening.
Courtesy USDA Agricultural Research Service


What a difference domestication makes
How can you distinguish domesticated grains at archeological sites from wild grains? Because -- and here we come to the genetic effects of domestication -- farmers create permanent changes while they tame wild cereals.

No two alike, a pile of corn cobs with multi-colored seeds.By the very act of sowing and harvesting crops, people are carrying out selective breeding, and that causes genetic and structural changes. Indeed, Charles Darwin used domestication to demonstrate that repeatedly selecting for certain traits could irrevocably change plants and animals.

Think of it this way: If you plant seeds in a garden, and then replant the seeds you grow, you are unconsciously selecting for crops that grow well in garden conditions. Plants that do poorly will disappear in short order.

Converting a wild plant or animal into a crop takes time and effort, because the wild ones have problematic traits. Wild plants, for example, often:

carry toxic chemicals as protection against insects or browsers.

have an inedible covering on the seed.

can be hard to harvest. Wild cereals, for example, shatter (fall apart) when picked. While shattering spreads seeds and helps plants survive in the wild, it makes gathering seeds a nightmare.

But when the early farmers grabbed a bunch of stalks and cut them with a sickle, the seeds with a weak connection dropped off. We can expect that the seeds the farmer planted next year would have a strong connection between the grain and the stalk.

A black-and-white Holstein cow stares at the camera.Eventually, that kind of selection caused a genetic change in the crop, and a strong connection (technically called the rachis) is indeed a sign of domesticated wheat.

Similarly, the aurochs that were domesticated into cattle were a fairly fierce crew, and we can presume that early farmers chose the most docile animals. Their descendants are being milked right now in America's Dairyland.

Moo! Did agriculture make a difference in human history?


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