Each category of living organism has difference quality of strains. let's take plants for example, you can find better oranges or corns be naturally grown on California than on Japan using the same seeds, due to thousands of factors like water, sun, wind, latitude, humidity...etc. It works the same as in other living organism like mammals or birds. To control a quality of a strain or produce a better strain is just a work of providing as good condition as possible for the organism. So now, how about the human strain? How to provide a good condition for human in order to reproduce a better strain? And what are the so called "good condition" refereing to humanity? Could be something stimulate you to build good health, agility, mentality... etc. So, to reproduce better offspring for making better strain of your own, you better pay effort on those aspects. Physical execise, gaining experience in life to build wisdom, knowing human history, knowing art...etc. Those would be some elements for creating "good condition". Smoke dope as well of course.
Plants dont have brains so its a little different. Organisms like trees and plants share traits with their parents and become whatever the most dominative traits were in them. Animals share the same idea, but they have brains and their own thought patterns. Their parents still show them the ropes and instinct plays a big role, but offspring never completely model after their parents. Humans are even more complicated because we don't live by instinct anymore, we have society to blame for that. How we are is entirely up to us.
