How could natural selection affect humans?

Explanation:

an example is the ability to endure the sugar, lactose, in milk. In many places of the world, people can't drink milk in light of the fact that their body turns off the intestinal creation of lactase, a chemical that processes the sugar in the milk.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms