Farmers remove weeds from their crops. But they miss the weeds that look like crops. Over time, these weeds come to mimic the crops around them. And in some cases, they become crops themselves.
A Russian plant biologist, Nikolai Vavilov, first described this process (hence the name Vavilovian mimicry). The weeds that look most like the nearby crops are the weeds that survive and reproduce. Farmers are engaging in “unnatural selection,” inadvertently creating weeds that look like crops.
It’s not all bad for the farmers, though. Through generations of selection some of these weeds have actually become useful to us. Rye and oats used to be weeds in wheat and barley fields. Now they have evolved into crops themselves and are weeds no longer.