A reader writes with questions about evolution.
What makes things evolve?
Animals and plants evolve because their bodies are controlled by genes which occasionally experience random changes known as mutations. Some of these changes are good for survival, some are not. The creatures that have the most favorable genes are more likely to survive and pass their genes to the next generation. This causes creatures to gradually change into a form that best allows them to survive in their environment.
Why did man develop, and yet monkeys still exist? Did the monkeys who did evolve into men, simply have different environmental conditions than the monkeys who didn't?
Well, we really didn't come from monkeys. Rather, monkeys, apes, and humans all descended from a common ancestor (which, incidentally, was probably close to modern monkeys). The various offspring of this ancestor ended up exploiting various niches of nature to earn their survival. And so they diversified into many species, each with its own niche. Monkeys continue to survive in the tops of the jungles, finding plenty of food up there and quickly scrambling from tree to tree to escape predators. Humans would not do good in that enviroment.So we have both humans and monkeys, each surviving in a different way in a different environment.
Are we really just an accidental mutation, or do other forces cause such changes?
The mutations are random. However the forces of selection for survival drive the creatures to survive in their niche.
Why do some animals like crocodiles stay the same for hunderds of thousands of years?
Once an animal has become well established in a large niche, if that environment remains stable, the physical changes to that creature often become small. Thus since sharks and crocodiles have evolved to be well adapted to particular stable roles in the environment, they have little need of further change. There genes continue to mutate, but the forces of natural selection hold the physical forms ofthe creautres stable with time.
Scientists do admit that it seems there were evolutionary jumps from one species to another, so what makes this happen?
Jumps occur when isolated populations find themselves in a different environment. Creatures sometimes change "rapidly" to meet the new requirments. These changes actually take thousands of years, but compared to the age of the earth, the change is relatively rapid. A good picture of how this happens can be seen in the various dog breeds. Most of these breeds developed in the last several thousand years as humans guided their environment and selected those that they wanted to breed. Thus in a few thousand years, we see great differences in the dogs. Should this breeding continue, we will one day have many different species of dogs with different characteristics.
Will we humans evolve into something else in a million years, and if so what drives it exactlly?
Certainly human genes will be different in a million years. The extent and direction of the changes depend on the environment. Interestingly, we as humans can affect our environment, and thus can influence the future or our species.
Is there one or two books that could explain evolution for me, in simple terms?
I would begin at the Talk.Origins Archive. Also, many have found The Selfish Gene and The Blind Watchmaker by Richard Dawkins to be good introductory books to the mechanisms of evolution.