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Earth Science

Humans Evolving Faster Than Ever 253

Posted by timothy
from the nerdrage-in-three-two-one dept.
Kwyj1b0 writes "In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up. Recent papers show that rare genetic variations have a more drastic effect than previously believed. Another result shows that 'we carry a much larger load of deleterious variants' (as well as positive variants) than our ancestors 200 generations ago."
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Humans Evolving Faster Than Ever

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  • by binarstu (720435) on Saturday December 01, 2012 @04:56AM (#42153133)

    The parent is simply wrong. Acquisition of mutations most certainly is evolution, and evolution does not require natural selection.

    Natural selection is one mechanism of evolution, but not the only one, and evolution does not have to increase fitness. Ever since the "modern evolutionary synthesis," evolution is often defined as the change of allele frequencies in a population over time. Such change might be due to natural selection, or it might be due to other non-selective forces, such as genetic drift. To say that again, natural selection is not required for evolution. Introduction of new alleles due to mutations, random fixation or loss of alleles due to genetic drift, changes in allele frequencies due to population bottleneck events, and so on, all can cause evolution without natural selection.

    Wikipedia has more information about natural selection and non-selective factors contributing to evolutionary change [wikipedia.org].

  • by dvice_null (981029) on Saturday December 01, 2012 @08:24AM (#42153783)

    > Software engineering does not introduce random mutations into the Software and then selects the mutations that made a the Software a little bit more useable

    I think the he was talking about evolutionary algorithms: http://en.wikipedia.org/wiki/Evolutionary_algorithm [wikipedia.org]

  • by SpinyNorman (33776) on Saturday December 01, 2012 @08:46AM (#42153859)

    In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up.

    This statement appears to reflect a misunderstanding of how evolution plays out in practice.

    The way evolution is often taught is that the small genetic changes in each generation make a difference to the evolutionary fitness (relative to his/her peers) of the individual right away, but that the changes are so small that it takes very many generations to see divergence of sub-populations of the species and hence noticeable evolutionary change.

    The reality of evolution - "puntuated equilibrium" - is different from this simplistic teaching model. What really happens is that genetic changes accumulate over very many generations but don't have much if any immediate effect on evolutionary fitness since in practice these small, incremental, personal changes are often not what drives evolution. What really drives evolution (per the inference of the fossil record) is when the *environment* (weather, food supply, disease, competitors, etc, etc) changes, often very quickly, causing accumulated genetic change to suddenly become relevant... what had previously been a benign genetic change (disease resistance or susceptibility, etc, etc) no suddenly becomes a huge change in evolutionary fitness in the new environment, and and the fate of different genetic subpopulations becomes very differnt (we see visible divergence).

    This is "punctuated equlibrium" - long spans of no visible evolutionary change (equilibrium) are puntuated by brief spans of rapid visible change as accumulated genetic drift suddenly becomes relevant due to environmental change.

    So... the notion of 200 generations being too quick for "natural selection to keep up" is bogus. Natural selection mosltly doesn't happen every generation - it only happens when those infrequent major environmental changes occur.

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