Too many good mutations can actually be bad for a species’ evolution

Mutation is one of the big driving forces behind evolution, as it can allow species to quickly gain the genetic tools necessary to survive and adapt. But even the perfect mutation can mean trouble if it can’t work with others.

That’s the finding of researchers at the University of Houston, who recently concluded a five-year study on a bacterial culture. Over approximately a thousand generations, these bacteria have become far better adapted to their environment, with their overall fitness increasingly by an estimated 35%.

The researchers identified the various mutations that have crept into the bacteria gene pool, and then they tried to figure out which combinations of mutations had the most positive effect. They found that the more mutations got added to the mix, the more they interfered with each other, even when – indeed, especially when – the mutations were all trying to solve the same basic problem.

A bunch of positive mutations could easily become a net negative if they didn’t fit well together. Moreover, the researchers found that the effect of any given mutation on the bacteria’s fitness would vary wildly depending on what other mutations were present. Lead researcher Tim Cooper explains:

“These results point us toward expecting to see the rate of a population’s fitness declining over time even with the continual addition of new beneficial mutations. As we sometimes see in sports, a group of individual stars doesn’t necessarily make a great team.”

via Too many good mutations can actually be bad for a species’ evolution.

This entry was posted in Biology, Evolution. Bookmark the permalink.

2 Responses to Too many good mutations can actually be bad for a species’ evolution

  1. alfy says:

    It is a popular misconception that evolution is “driven” by mutation. It isn’t. It is NORMAL VARIATION which provides the wide range of possibilities upon which natural selection works. That is, the existence of several different alleles (variations) of a particular gene produces a number of different phenotypes (physical types).

    Take the ABO blood group gene. Very simply, there are three alleles, A, B, and O. They can be combined two at a time (one maternal, one paternal) to form six genotypes AA, AB, AO, BB,BO, and OO. These result in only four phenotypes, an “A” person (AA, or AO), a “B” person (BB or BO), an “AB” person (AB only) and fourthly an “O” person (OO only).

    Now, for the sake of argument, if every gene only produced four phenotypes, when taken in independent combination, 2 genes would create 16 phenotypes and 3 genes would create 64 phenotypes. Do you see that with a few thousand genes the number of possible phenotypes is astronomical? This is the basis of normal variation.

    As you may imagine the picture is rather more complex than I have suggested here but the broad principles are correct. Mutation does have a part to play in evolution but it is a very minor one, because most mutations are damaging to the organism.

    This interesting bacterial work at Houston bears out what I have said. The researchers appear to be surprised by their results, which would be the case if they believed the erroneous proposition at the head of the posting. Evolution is not driven by mutation.

  2. Deskarati says:

    Thanks Alfy, so its One – Nil to genetic recombination.

Comments are closed.