I read somewhere about a type of moth that is colored either white, or brown.  It all depends on the trees in the area where they live.  If the trees are birch trees, with white trunks, the brown moths land on the tree trunks and are picked off by birds because the birds can see them.  The white moths don’t show up on white tree trunks, don’t get picked off and they survive to reproduce.   And in a few generations, white moths become predominant because that “white” gene is the one that gets passed on to the next generation.  

In the same way, if the area has trees with brown trunks, the birds can see the white members of the moth species, swoop in and eat them and the white moths don’t live to reproduce.  After a few generations, only brown moths are present.  All because of the color of the tree trunks.  And birds that eat moths.

This process has a name.  Natural selection.

Another example of natural selection is seen in a human’s wisdom teeth. Years and years ago, in our primitive past, if you didn’t have wisdom teeth, you couldn’t survive very well without them. You needed those extra teeth to gnaw meat from bones.  As our living conditions and nutrition improved, the lack of the “wisdom tooth gene” no longer led to your death from hunger.  Today, there are people who never grow wisdom teeth at all.  There are also people who grow only two, and there are still people who have all four.  We actually don’t need them anymore and the gene for four wisdom teeth is not as predominate.  That’s Natural Selection in action.