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Evolution = years of natural selection?

  1. Jul 12, 2005 #1

    Pengwuino

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    Someone posted in another forum that "Evolution is the result of hundreds of thousands of years of natural selection." Is that true?
     
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  3. Jul 12, 2005 #2

    brewnog

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    Yeah, definitely.

    We evolve because those characteristics which cause us to be better at breeding or surviving give us an advantage over those which do not have such beneficial traits. As a result, the genes of the individuals with beneficial characteristics are passed on. It really is a case of 'survival of the fittest'.
     
  4. Jul 12, 2005 #3
    "Is that true?"

    Which part?

    Evolution depends on random mutation and selection. The selection can be natural or artificial or sexual.

    Adaptation can occur quickly (think drug-resistant bacteria arising in a matter of days) and represents a shift in the gene pool of a population. (A population should be genetically isolated from other populations of the species, in order for the gene pool changes to eventually lead to two distinct species. )

    Given enough time, and enough of these sorts of shifts in the gene pool, (and some sort of genetic isolation of the population) speciation can occur. Species boundaries are fuzzy, though, so whether evolution requires days, thousands of years, or hundreds of thousands of years is probably more a matter of personal opinion than anything.
     
  5. Jul 12, 2005 #4

    iansmith

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    Years is not the best way to measure evolution.

    Generation is the best way. Bacteria might becomes resistance to antibiotics in the matter of days but several generation has occurs. So when compare to other organism the rate might be more less similar.
     
  6. Jul 12, 2005 #5

    Moonbear

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    Natural selection is a part of the process of evolution, but it is not the ONLY thing. Evolution is also a continually ongoing process (it really is a process not just an end result), so as iansmith pointed out, you wouldn't really measure it in years. Indeed, because it is a process, you would measure that evolution occurred by the observed changes in populations of species.
     
  7. Jul 12, 2005 #6
    Well, first I'd like to have a qeustion that may have to go unanswered. How long approximatly did it take for the single celled organisms to change into something like say a fish. Probably quite some time I'm guessing. Now, how long have humans been estimated to walk the earth? Also for quite some time. We had the cave men (big scary lookin dudes that had thicker skulls and bones than what we have today) and now we have ourselves (slightly smaller in stature but we have a larger brain that also comes in handy). To me that is an example of adaptation, not evolution. Some of you may beg to differ and that's ok. You are entitled to it. To me evolution is more of a change from one species to another. Now to pose the Q. Are we a different species than that of early man? Did natural selection make us the way we are? And if we did in fact come from single celled organisms, why havn't we changed into some other type of creature completly? You're answers or thoughts would be appreciated. (sorry if it's a little [or a lot] off topic.)
     
  8. Jul 12, 2005 #7

    James R

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    Roughly, a couple of billion years.

    From memory, a few hundred thousand years.

    Adaptation is one part of evolution. Speciation is another. They both happen the same way.

    Depends how far back you go. Mostly "early man" refers to early Homo sapiens, so the answer is probably "No." But go back a bit further and you find Homo neanderthalis, Homo erectus, Homo helidelbergensis and others. Go even further back and you find Australopithecus, a kind of half-ape, half-man. Back further, you find our common ancestors with modern apes such as chimpazees and gorillas.

    Yes. And some lucky accidents.

    Not enough time. But we're still evolving.
     
  9. Jul 13, 2005 #8

    Phobos

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    There are several mechanisms that produce evolutionary changes...natural selection is one of the mechanisms.

    :confused: Aren't we already very different than single celled organisms?

    Perhaps you meant 'why hasn't H. sapiens changed into something else yet?' It takes time. We are still evolving.

    Or perhaps you meant 'why are we still so similar to single celled organisms? (e.g., same base nucleotides in our DNA and many common biochemical processes)' That's a mark of common descent (evidence of common ancestry).
     
  10. Jul 13, 2005 #9
     
    Last edited: Jul 13, 2005
  11. Jul 13, 2005 #10

    saltydog

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    Not really. It's survival of the fittest: the ones you don't see walking around died off. And as far as apes getting much further, we'd stop them if push came to shove. Let's say all humans were removed from the face of the earth. If conditions favored it, I could imagine apes maybe evolving into something more intelligent, maybe man-like all over again but it's really pure luck so I'm not convinced.
     
    Last edited by a moderator: Jul 13, 2005
  12. Jul 13, 2005 #11
    Man are apes. What would a half-man, half ape look like? A chimp? Perhaps... an aborigine? A pygmy? A Homo floresiensis? http://news.nationalgeographic.com/news/2004/10/1027_041027_homo_floresiensis.html

    What would a half-monkey/half man look like? A gorilla?

    Try this: H. sapiens indigenous to Africa (intense UV radiation) is dark skinned. H. sapiens indigenous to Norway (considerably less UV radiation) is light skinned.

    H. sapiens indigenous to Africa has a high frequency of the sickle cell allele because it is resistant to malaria, which is endemic in Africa. H. sapiens in Norway, does not.

    H. sapiens in Africa (hot) tends toward ectothermic (tall and skinny). H. sapiens in Norway (cold) tends the opposite direction.

    If you want examples you can look at in the here and now, these are good places to start. More available upon request.

    If you want to see us change into a new species, plan on sticking around through (1) several hundred thousand years, (2) a population crash down to 1% of what we currently have and (3) a different environment than what we experience, now. Without those sorts of changes (and time) you won't see it.
     
    Last edited: Jul 13, 2005
  13. Jul 13, 2005 #12

    Pengwuino

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    A rock star? :rofl: :rofl: :rofl:

    Thanks for hte information guys
     
  14. Jul 14, 2005 #13
    pattylou "Man are apes. What would a half-man, half ape look like? A chimp? Perhaps... an aborigine? A pygmy? A Homo floresiensis?"

    Well I must disagree with that.

    pattylou"If you want to see us change into a new species, plan on sticking around through (1) several hundred thousand years, (2) a population crash down to 1% of what we currently have and (3) a different environment than what we experience, now. Without those sorts of changes (and time) you won't see it."

    I wish I could.
     
  15. Jul 15, 2005 #14

    Phobos

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    We've only been here for about 200,000 years. Big changes can take more time for slow breeding creatures such as ourselves. But over that time, we've diversified into many varieties (all the different human 'races' around the world...African, Asian, Pacific Islander, Caucasian, Indian, Inuit, etc.). Racial lines are now blurring. And remember that outward appearance is just part of the game. There's also things like the immune system that change in response to different external pressures.

    One thing about current human evolution is that our technology may be slowing it down. More dramatic evolutionary steps usually take place in an isolated group or after a dramatic environmental change. We have some control over the environment with our technology and there aren't many isolated human groups left given our transportation technologies.

    Note there there is no "higher" or "more advanced" scale in evolution nor is there a pre-set direction toward a specific goal other than adaptation to local conditions. An ape change toward or away from 'human' would be equally valid.

    But within your lifetime, you can see evolutionary changes such as bacterial resistances to antibiotics, insect resistances to pesticides, etc.

    Given what I said about there being no pre-set scale, reconsider what pattylou has asked.

    But let me throw some wildcards on the table...
    Are marine mammals half land animal/half sea creature?
    Are crocs and alligators half land animal/half aquatic?
    Are flying squirrels (etc.) half land animal/half flying?
    Are mudskippers and lungfish half fish/half land animal?
    Is the hippo making the transition from land back to sea?

    A key to the theory of evolution is the diversity of life forms...there are a spectrum of traits...evolution is not a linear ladder to be climbed so "half-human/half-ape" doesn't really make sense.

    Another thing about humans, we are the last remaining species in our genus (which could be considered a mark of evolutionary failure by some measures). Other modern apes are of a whole separate genus (indicating that our common ancestor is further back in time). Tens of thousands of years ago, there were other human species that co-existed with us but they have since died out. So when we look at ourselves, we appear more separated from other animals. The spectrum of variations between us and other apes has been pruned away.
     
  16. Jul 16, 2005 #15
    The question was raised as to how long it would take for us to evolve from single celled organisms when we actually are made up of them.

    Dude, you seem to think we did not evolve from a more primitive primate! What was the process you imagine does account for our change?

    Our age? We humans are now believed to be almost 200,000 years old. That means that we have been basically unchanged, biologically, all that time. The evolution that occured was all before then and is what made us what we are. What we have achieved since then has nothing to do with biological evolution. Instead, it is social evolution and a very different process.

    charles
     
  17. Jul 18, 2005 #16
    Natural selection + Reproduction + Long periods of time = Evolution
     
  18. Jul 19, 2005 #17

    Phobos

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    Welcome to Physics Forums, AMF8! :smile:

    couple things...

    Evolution can be defined as the change in the frequency of alleles (gene types...e.g., short vs. tall) in a population....so in that sense, evolution can happen very quickly. For example, the shapes of the beaks of "Darwin's finches" change from year to year based on climate and we have witnessed antibiotic-resistances/pesticide resistances develop in pests within a matter of years. But yeah, speciation, or changes at higher taxonomic levels typically take long time periods.

    In your equation, "reproduction" needs to include some mechanism for increasing genetic variations...perhaps its straightforward gene recombination (mixing of mom's & dad's genes) and gene flow (influx of genes from another population) but it should also include mutation (creation of new/modified genes). Sometimes all those factos are lumped under "mutation" (referring to an overall change in genetic code). Natural selection acts to reduce a population's variations (favoring the better adapted forms for the current environmental conditions). Sometimes other variation-reducing mechanisms (e.g., sexual selection) are lumped under natural selection. So, we could say...

    mutation + natural selection = evolution
     
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