Mutation, Not Natural Selection, Drives Evolution
I just read the above article in Discover (link: March 16, 2014) that captured my curiosity. Famed population geneticist Masatoshi Nei claims that evolutionary biology has overly relied on "natural selection" as the brand name for evolution, and he makes a fair argument. He suggests an alternative - mutation driven evolution - that can seem subtle in comparison to natural selection at first glance, but it is not subtle. Why would biologists revise their heavy use of natural selection in favor of evolution by mutation?
- First, mutations come before natural selection. Without genetic variation, there can be no change in an organism that is directed by natural selection. Nei states:
Mutation means a change in DNA through, for example, substitution or insertion [of nucleotides]. First you have to have change, and then natural selection may operate or may not operate. I say mutation is the most important, driving force of evolution. Natural selection occurs sometimes, of course, because some types of variations are better than others, but mutation created the different types. Natural selection is secondary.
- Second, evolution by natural selection ignores that some variation arises by neutral mutations (that have no effect on the organisms' function) and population size crashes can cause those mutations to spread. So why would biology want a universal brand name like Natural Selection that misses the "neutral" side of evolution?
- Third, it is Nei's opinion that natural selection is a deterministic force that simply replaces the hand of God as that deterministic force. Herein lies something important to consider.
If you say evolution occurs by natural selection, it looks scientific compared with saying God created everything. Now they say natural selection created everything, but they don’t explain how. If it’s science, you have to explain every step. That’s why I was unhappy. Just a replacement of God with natural selection doesn’t change very much. You have to explain how.
Part of the crux of the theory of evolution is that random mutations arise in a manner that is inconsistent with a deterministic hand. Changes are not orchestrated by want of a higher power but by random genetic processes that cause errors in the DNA code. It's equivalent to the randomness of the universe.
My favorite Nei quote is at the end. It is a message for all students of science:
But any time a scientific theory is treated like dogma, you have to question it. The dogma of natural selection has existed a long time. Most people have not questioned it. Most textbooks still state this is so. Most students are educated with these books.
You have to question dogma. Use common sense. You have to think for yourself, without preconceptions. That is what’s important in science.