Evolution mainly consist of three steps, I will try to explain it to the best of my ability.
Step 1, certain biological traits are inherited by genetic means;
Step 2, mutations in genes and gene recombination produce variations in those traits;
Step 3, Some of those variations produce more fit to survive genes than others.
As the more fit genes survive they end up reproducing more of themselves. So in turn the frequency of surviving gene variants increase in the population. It is a common misconception that evolution favors survival of the fittest. Evolution is about reproducing, passing on copies of genes. The difference between survival and reproduction is seen in something called antagonistic pleiotropy. (Antagonistic pleiotropy is when one gene controls for more than one trait where at least one of these traits is beneficial to the organism’s fitness and at least one is detrimental to the organism’s fitness.)
Two examples of this are primates and salmon. Primates prostates have high metabolic rates, enhancing sperm motility… this is great for fertility and reproducing but not great for the primate because it enhances the chances of prostate cancer. Salmon travel to their spawning grounds to copy their genetics then literally die. If evolution was about survival rather than producing copies of genes we wouldn’t have antagonistic pleiotropy. People wouldn’t be reproducing as often as they do because it would be easier to survive feeding and protecting less. Another misconception is that the current surviving life on this planet is somehow more evolved or fit than the extinct ancestors.
Everything adapts to what’s around it, everything adapts to what the environment is now. Everything that is extinct was well adapted to the environment, it was the changes to that environment that ended them. Finally, it is a common misconception that evolution directly selects for greater complexity. This is not always the case. A bacterial plague isn’t complex and in our history it has wiped out entire cultures. Many people believe that evolution is just a theory. However, we see it in bacterias becoming resistant to antibiotics, insects with short generation times splitting into two. We see it in our genetic similarities…like sharing 98% of our genes with apes, 96% with monkeys, 75% with dogs, 20% with the common fruit fly. These numbers showing us that our more common ancestor is with apes, then monkeys, then dogs, then fruit flies, etc… all the way down to bacteria by thermal vents.
