• Question from:Christopher

Hi, I have a question about genetics and evolution that I have been struggling to figure out i recent years.

All species adapt to survive, and they to that through mutation and evolution (very roughly) but my question is, what mechanism in the genes or body decides what mutation takes place on the body of the individual animal?

Recently I watched a documentary on Animal Planet about South America and the evolution of the animals there. Now take the giant ant eater. It has extra joints between it's vertebra to reinforce it's back when it's eating termites. Now how did the body figure out that extra joints in the back were the best solution to that problem? Also, the ant eaters jaws are "sealed" by the skin so it can't open it's mouth apart from the front where it's tounge gathers termites.  Again, what mechanism decides what mutation is best for the animal, and how does the body itself figure out exactly what mutation is the best for it's survival?

Is it a question of trial and error? Of course I understand that almost every animal is constantly evolving to suit the enviroment it lives in, but I think it's an interesting question.

I hope my question makes sense.

Best regards
Christopher Hower - Denmark.

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  • University of East Anglia
  • Posts: 139

Hi Christopher,
The confusion here stems from a misconception of the process of mutation and natural selection. Evolution is not a guided process and animals do not develope mutations to suit a need. Mutations happen regardless of "need" and most are incredibly harmful, think of the many genetic diseases in humans. However very occasionally mutations occur which can confer a small advantage to an organism, natural selection is then the name given to the process by which those organisms which have traits that improve their survival leave more offspring on average than other members of the same species. It is the steady accumulation of small mutations coupled with natural selection which removes bad mutations (organisms carrying those mutated genes die or leave fewer offspring), while selecting for beneficial mutations, that eventually leads to the development of complex traits that benefit the organism.

  • University of Waikato, Hamilton, New Zealand
  • Posts: 307

Evolution is absolutely a process of trial and error, though that phrase doesn't really capture the subtlety of natural selection.

A good analogy for the process described by Phil is rolling six dice. Suppose that you see someone who has just rolled six sixes, which is fairly unlikely. But what if you only had to roll one dice at a time, just saving the sixes and re-rolling all others? The chances of arriving at the desired result is dramatically increased.

Evolution is a mechanism by which our hypothetical dice already showing six are retained, and all others are re-rolled. In this analogy, mutation equates to rolling the dice, and natural selection equates to picking out only the sixes.

Of course, in the real world, it isn't quite so black and white. As Phil said, only small benefits are needed for a mutation to be selected for, and you don't need to arrive at a finished product in a single step. Something only slightly better than the status quo is needed. Similarly, deleterious mutations don't need to be very bad to be selected out.

In our dice analogy, you can think about this like rolling a dice and keeping the result if it is a higer number than previously, not just if it is a six. Getting a lower number equates to a deleterious mutation, getting a higher equates to an advantageous mutation. In this way the six dice will go from random numbers to high numbers and eventually to all sixes.

Evolution plays dice with billions of four-sided dice, but it cheats as much as it possibly can!