Natural Selection is about adapting to one's environment because the biology in the organism (which is already there) is being shifted around for an animal (for example) to survive better in a given environment.
And because Natural Selection goes on, it causes genetic information to decrease and not increase! Genetic information will NEVER and has NEVER increased through Natural Selection as Natural Selection just helps things survive better by shifting their own biology around but no matter how much this goes on, it will NEVER change the genome or increase genetic information!
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Sage ♋ ♓ ♐ say: So, first of all, evolution takes an extremely long time to be able to observe noticeable changes, and air pollution caused by infrastructure hasn't been around long enough to naturally select people who don't get asthma even in harsh air conditions.
Second, the human species evolved in an environment that had a constantly changing climate. Suddenly, it wasn't obvious who the survivors would be, since within the course of a single lifetime the same area would flood and drought and grow trees and lose trees, any creature that was supremely adapted towards just one of those environments would die out or leave when the climate changed. Natural selection selected toward creatures who could not only survive/thrive in one environment, but survive/thrive in a variety of environments using superior problem solving skills. This is when our primate (not monkey, monkeys are a type of primates, and so are modern humans, primate and monkey are not the same thing) ancestors who already had bigger brains than most animals, started naturally selecting for larger brains until eventually homo sapiens (modern humans) emerged. This process took a very very very long time and there were many species of human-like primates that lived and died out, many of which lived significantly longer than humans have been around, but still died out naturally before we came around. There were other similar species to us, we are just the newest, and most successful, of the two-legged big-brained primates. They weren't "half-person/half-monkey" since we weren't evolved from monkeys, we're like they're cousins. We're both descended from a species that no longer exists that branched off into two separate divisions. The side of the "family" that was more monkey than human eventually became all of the species of apes and monkeys alive today. The side of the family that was more human (not quite human, just more human than the monkey side) had several "generations" before humans came along. Homo habilis, homo erectus, and Neanderthals, are all examples of species who are more similar to us than monkeys, but still not quite human, just for various reasons, they're extinct, whereas humans are still around.