The trajectory of evolution

quasispecies-selectionScientists and philosophers have long debated the trajectory of evolution. Some of the questions they consider include: is there a predictable direction for evolution, and if there is, what is the pathway? Are there evolutionary dead ends?

Viruses are excellent subjects for the study of evolution: they have short generation times, high yields of offspring, and prodigious levels of mutation, recombination, and reassortment. Furthermore, selection pressures can be readily applied in the laboratory, and may be often be identified in nature.

When studying evolution of viruses, it is important to avoid judging outcomes as ‘good’ or ‘bad’. Anthropormorphic assessments of virus evolution come naturally to humans, but concluding that viruses become ‘better adapted’ to their hosts, for example, fails to recognize the main goal of evolution: survival. Or, in the case of the non-living viruses, existence.

Evolution does not move a viral genome from simple to complex, or along a trajectory aimed at perfection. Change comes about by eliminating those viruses that are not well adapted for the current conditions, not by building something that will fare better tomorrow.

Comments on this entry are closed.

  • lantrix 11 June 2009, 7:08 pm

    It seems one can equate “Change comes about by eliminating those viruses that are not well adapted for the current condition” as effectively survival of the fittest – or in Darwinian terms natural selection.

  • profvrr 12 June 2009, 5:15 am

    Yes, you are correct – but the selection comes about because of the
    current conditions, not from trying to make a better virus for the
    future.

    On Thu, Jun 11, 2009 at 10:09 PM,

  • Thomas Overton 13 June 2009, 12:24 pm

    Quite true, in fact, a trajectory of perfection cannot exist as viruses have a limited energy reservoir where they have to make the 'choice' of which life history trait(s) to cater to based on the selection pressure(s). With every gain there is a loss–tradeoffs make leaps in complexity difficult and attainment of perfection impossible.

  • gsgs 15 June 2009, 1:28 am

    and the way how to mutate is itself subject to evolution…
    As a programmer you may try to optimize a mathematical entity through
    small changes, using a “genetical algorithm”. You have several parameters
    how to best perform these small changes and the task is to finetune these
    for optimal evolution speed. I feel that the viruses are not optimal here yet
    and that other ideas for changing genetical material and remembering and optimizing the
    parameters, may lead to much “better” viruses, which will then out-evolve the old ones.
    This may be done artificially…

  • lantrix 15 June 2009, 11:17 pm

    Seems like this applies to homo-sapiens as well. Current conditions cause the selection 🙁

  • Bio Breakaway 16 June 2009, 6:17 am

    Seems like this applies to homo-sapiens as well. Current conditions cause the selection 🙁