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Wierd question about evolution

  1. Dec 2, 2005 #1
    This is a question geared toward human evolution, but I figured a biologist would be able to answer it. There are two parts:

    1. If supposedly, we physically evolved (less hair, stand up straight, etc.) because we changed our behaviour, would it be safe to say that generally, as something mentally evolves, it physically evolves? Does intelligence cause physical evolution? (of course over a long period of time).
    2. Furthermore, if this is true, could it be possible for humans to physically de-evolve back into more ape-like animals if for some reason we mentally became more ape-like (for example, if all forms of communication and education were somehow lost)?

    As is obvious I am not an expert in any respect, just curious.
  2. jcsd
  3. Dec 2, 2005 #2


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    The only thing that is selected for is the total effect of the environment on reproductive success. So yes, if behavior caused a different environment to be available then that behavior change could make different genetic variation selectable than before.

    We could very well evolve into something less communicative and organized than we are now, but it would be so improbably as to be FAPP impossible for us to retrace our evolution steps as such. Morlocks are a possible future for us but not chimps. In fact it's wrong to think of chimps as a simpler version of us. They have evolved away from our 6 million years ago common ancestor just as we have.
  4. Dec 2, 2005 #3


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    I recall hearing that koalas have "de-evolved" from their ancestors. Certain life aspects that they have adopted, which include a specialization to eating only a single food type, i.e. eucalyptus leaves, have led them to lose brain volume since they no longer need/use it. I'll have to do some searching to confirm this.
  5. Dec 3, 2005 #4
    wow thanks

    I totally appreciate the tool quote because somehow it's totally relevant. Anyway, I would love to hear what has happened to koalas (the thing about how they have lost brain mass, or whatever it was), and also, what in the world is a "morlock"?
    I was not necessarily suggesting that we would de-evolve back into chimps, I just wanted to confirm that maybe it would be possible to change into something less communicable and organized, as you said, than we already are.
    Another follow up question might be this: if it would be possible for humans as a whole to evolve into a different state, then would it be possible, given that a large part of the population died out and was separated over large geographical distances, for different groups of humans to "de-evolve" at different rates due to different environment and so forth, and in essence create strata of levels of similiarity to modern humanity? Or in other words for humanity to split into significantly different species?
    Thanks again your answers have been very helpful.
  6. Dec 3, 2005 #5


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    Well, sonny (:tongue2:), there was a British writer named H.G. Wells, and he wrote a book called The Time Machine. In the book there was a fictional species called the Morlocks who were said to have descended from humans, although they have evolved to become a completely different species by the 8028th century. They were kind of like chimanzee-neandertal things, I think. They "de-evolved" into the Morlock species from the human species because for some reason people moved underground.
    Last edited: Dec 3, 2005
  7. Dec 5, 2005 #6
    It's hard to say. Within human evolution physical and cultural evolution have been closely intertwined, and both have affected one another.
    As for de-evolving? Well I actually don't like using that word. While there are examples of decrease in brainsize in evolution, or other traits that a person might consider what make up a "more evolved" organism, it is neccessary to keep in mind that all adaptations come with compromises. While we evolved bipedal feet, you might say that we "de-evolved" the ability to nimbly climb trees like our predecessors.
    Also I believe it would be very difficult for a species like human beings to lose something like culture. Culture is something that made us especially successful as species, and is something that evolved far back. There are many examples of cultures in our primate cousins. All Haplorhines (or Anthropoids) share complex cultures, although it is in a much greater complexity in humans.
    Now to lose technology from some sort of catastrophic event and the ability to build it is possible, especially as we become more specialized. I know many software buffs who couldn't build a computer. And it is equally likely that the population in question would never be able to relearn that technology -- that it is lost forever. "Greek fire" might be an example for that. From what I can remember we still haven't found out what exactly it was, and we may never know.
    I'd agree with your different types of human-like organisms from an original human population, as long as those new species are isolated from each other. As an example (although contraversial) there were populations of australopithecines that were extremely morphologically different from one another, and some anthropologists suggest that they were isolated sufficiently for different species.
  8. Dec 12, 2005 #7


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    I too recommend against using the word "de-evolve". Evolution is simply change. There is no direction implied other than adaptation to current environments/ecosystems (good example about humans "de-evolving" the ability to climb trees).

    If, in a future environment, being more "ape-like" is more beneficial to reproduction and survival than our current form is, then such a change would not be de-evolution (it would be a positive change as measured by the overall success of our species even if an individual regrets not being more intelligent, more hairless, or whatever).

    If you could get separate populations of humans for a long enough time, then yes, you could get a speciation event (divergence to the point where interbreeding doesn't, or can't, occur anymore).
  9. Dec 12, 2005 #8
    no this isn't how evolution works. This sort of runs parallel to the "use and disues theory" proposed by lyell a few centuries ago (keep in mind this theory was WRONG). You can think all day and night that you want a third arm protruding out of your chest, but it will never happen (well, at least as a result from thinking about it).

    I'll give you a quick rundown on how evolution works, in any organism. In every single cell in your body DNA is being transcribed [copied, replicated] over and over again until you die. These transfers make mistakes very rarely, one in a hundred million base pairs I believe, but seeing as there are over 100 trillion cells in your body, mutations are not at all uncommon to say the least. So mutations are happening all the time in both you and I - got it? The next step is evolutionary pressure. This pressure is applied with a new predator or changes in the enviornment. The only species to survive and pass on genes to the next generation are those who acquired a predisposed immunity via mutations to whatever pressure was applied.

    also, we did not evolve from monkeys. We share a common ancestry with monkeys.
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