Evolution is faster than I thought

Darwinian Fisheries, an article at WorldChanging, tells us how cod in the North-East Arctic have grown smaller in size adapting in favor of survival. The influence is that of a law which stipulates that only the larger fish can be caught. So the smaller cod have a higher chance of survival, and so cod are growing smaller.
(Cached article)

In other news, my blog is the first result for “Gotham comics India“, as a friend pointed out recently!

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5 Responses to Evolution is faster than I thought

  1. Arnaud R. says:

    Well, it’s not really correct to say that cods are growing smaller, and that they adapt in favour of survival. It’s a common misunderstanding of natural selection that evolution happens after a change of environment. It happens all the time. And the adaptation of a population is only its ability to have diverse enough individuals to survive in various situations. This is why biodiversity is so important.
    Let’s take a concrete example:
    100 cods in a normal situation (no overfishing). Let’s assume that there are 25 small ones, 50 average sized and 25 big ones. In the next generation, you’re likely to get more or less the same situation (25/50/25). Now let’s put tremendous pressure on part of the population and let’s kill 24 big cods, 45 average cods and 6 small cods. We’ll end up with a much smaller population (only 25 cods) with a majority of small ones (19/5/1). Has there been any evolution or adaptation? Not at the individual level (no genetic mutations, etc), but definitely at the population level.
    Do I make sense?

  2. Carthik says:

    Yes, you make sense, and it seems to me that the point you are making is that changes visible in the population, might not be genetic changes that will be seen in the species. But, maybe, in this case, the cods as a species have changed. Possible?

  3. Arnaud R. says:

    Genetically speaking, nothing has changed indeed. The differences were there before but some have been selected over the others by a change in environment (it’s pretty much always how evolution works: no reaction to the environment, only selection of already existing characters).
    Has the species changed? No (eventhough one could argue about the definition of “species”): men are taller than 100 years ago, but we still consider them to be the same species. Same with the cods.

  4. siddharth says:

    My understanding of evolution is that it involves both mutation and natural selection. Am I wrong? Also, are there no differences between the genes of the small cod and the large cod ?

  5. Arnaud R. says:

    You’re correct about mutations and selection. What’s very important to understand is that it is a process that constantly happens, but most of the mutations either don’t have any real effect either are lethal and disappear. Sometimes however you get mutations that have a positive effect (in a given environment) and they will tend to be selected and some of them will have a negative effect and there will be less of these. But if the environment changes, the individuals that were not so well adapted suddenly see themselves better adapted then others, hence more successful to reproduce, hence more numerous.

    About your second question, each individual has a different set of genes (except maybe clones en twins but that’s another story) but as a whole, it is the same: each cod has a set of genes that controls its size (which are positionned on the same chromosomes, etc, etc) but the combinations are different so that the sizes are different (my biology lessons are far away, and I’m not so sure of the exact terminology I should use and if I make myself understood).