Does evolution stop?

  1. I have a rudimentary understanding of evolution. Simply put it starts with chance and guided by natural selection which is not random. This is my understanding as of now not sure if its correct. In this video http://bigthink.com/videos/mankind-has-stopped-evolving-2 he says humans have stopped evolving. He relates evolution to 'evolutionary pressure' and goes on to state that since there is no pressure as of now there will be no more evolution. Going by my understanding it puzzles for 2 reasons a) evolutionary pressure has nothing to do with random mutation (why else they would call it random?) b) it is natural selection which selects the species which are good enough for that particular time/situation. Now how can one be sure that no more random mutation will occur in humans resulting in morphology he states which the natural selection will favor (like they become super intelligent and decide to eradicate humans). Am i missing something? Sorry for a lengthy post
     
  2. jcsd
  3. phinds

    phinds 9,136
    Gold Member

    I believe you are correct.
     
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  4. D H

    Staff: Mentor

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  5. Ygggdrasil

    Ygggdrasil 1,690
    Science Advisor

    At its core, biological evolution deals with how the frequencies of different alleles (gene variants) in a population change over time. Even though mutations are occurring all the time, these mutations do not constitute evolution unless they are able to become prevalent in a population. There are two main ways by which such mutations could spread throughout a population: natural selection or genetic drift. Under natural selection, mutations that confer selective advantage spread throughout the population because individual that carry these mutant alleles have more offspring than those who lack the allele. Under genetic drift, the mutation confers no advantage, but it becomes prevalent in a population through random chance.

    For both of these processes, the rate at which mutant alleles to become fixed in a population (i.e. for these alleles to outcompete all other versions of the gene), depends on the size of the population. Even alleles that provide strong fitness advantages will be fixed at slow rates in very large populations. Therefore, the large size of the human population (and the ease of mixing, so that no subpopulations can get isolated from the larger population) will make any significant changes to the human genome occur at an extremely slow rate. That is not to say that evolution has stopped; indeed, there are numerous examples of alleles that have become fixed rather recently in various populations throughout the world (for example, alleles for lactase persistence which allow individuals to digest milk sugars into adulthood, mutations in the CCR5 receptor which are thought to provide resistance to the plague and smallpox, and mutations in genes that affect alcohol metabolism. See http://www.nytimes.com/2010/07/20/science/20adapt.html for additional discussion).

    Under what conditions might we expect human evolution to occur more quickly (relatively speaking since evolution occurs on geological time scales)? See the following post for a more in depth discussion: https://www.physicsforums.com/showthread.php?p=4511126#post4511126. Note that new technologies may allow for artificial selection in human populations and could greatly speed human evolution in the near future.
     
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  6. I do not think life is possible without evolution. I do not think it is possible to create a living system that does not evolve given enough time. The Universe is not static. It changes and confers selective pressures however small or large and these pressures either naturally or artificially induced will have some impact on genetic diversity and gene frequency in any sufficiently large gene pool. If evolution stopped I believe life would eventually stop also. I suspect if and when one day we create artificial life, it too will evolve in its own way even if those life forms are not chemical.
     
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  7. Ryan_m_b

    Staff: Mentor

    Even if all natural selection was somehow minimised sexual selection and genetic drift would still drive evolution.
     
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  8. Evolution is generally a reaction to changes in niche availability. These changes may occur do to competition, changes in the supply chain, environmental shifts or over selection. Over selection is possibly the classic, with example of the sabre tooth tiger. Sexual Dimorphism and mate selection may also play a part, depending of the social complexity of the species.
     
  9. Yeah evolution doesn't stop it just slows down every once and a while
     
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