How does ISOLATION factor in Evolution?

Discussion in 'Biology & Genetics' started by Eflex tha Vybe Scientist, May 8, 2002.

  1. Eflex tha Vybe Scientist Registered Senior Member

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    I read recently that Isolated human populations are the ones most likely to produce significant changes in the genome.

    In addition, as humans continue to have mutli-Ethnic children, the chances for any significant Evolution of the species is hindered.

    The article also said that the first humans on isolated colonies on Mars or on the Moon will produce variation or significant mutation.

    HOW is this so?

    I always thought that the intermixing of different Ethnicities would INCREASE the chances of Evolution.

    can someone:
    scilosopher
    paulsamuel
    IamaHampster

    please explain Isolation?
     
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  3. kmguru Staff Member

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    That arguments taken to the extreme calls for incest as the best way to increase genetic variation. Looks like this is a case against multi-ethnic marriage...

    Was it published on April 1st (or could be done by a neo-nazi group).
     
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  5. Eflex tha Vybe Scientist Registered Senior Member

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    http://necsi.org/projects/evolution/evolution/change isolation/evolution_change isolation.html

    Change and Isolation


    Environmental change and isolation of groups of organisms play an important role in evolution.
    Erupting volcanoes cause sudden, drasitc change in an area, forcing organisms to evolve rapidly to adapt to the new environment.
    This penguin's ancestors looked much like other birds. As their environment became colder and wetter (possibly because of their migration), the birds evolved many traits to help them survive in the changed environment.
    Change in an organism's environment forces the organism to adapt to fit the new environment, eventually causing it to evolve into a new species. For example, if a species of animal is mostly limited to eating one kind of leaf, and a change occurs: a fungus attacks and kills most of that kind of plant, the animal has to evolve either to fight the fungus or to eat something else.
    Isolation means that organisms of the same species are separated, and happens when there is something between the organisms that they can't cross. Organisms become isolated as a result of environmental change. The cause of isolation can be gradual, like when mountains or deserts form, or continents split apart. It can also be quick, such as organisms being blown to different places by a storm or tsunami (tidal waves).

    When organisms become isolated the two groups are also not able to reproduce together, so variations and mutations that occur in one group are not necessarily found in the other group. The longer the groups are isolated, the more different they are. They eventually become different species. Moreover, if there is a change in the environment of one group it does not necessarily occur in the environment of the other. So they will evolve and adapt differently.
     
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  7. kmguru Staff Member

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    I can understand "Change" as a factor in adaptability and perhaps genetic variations, such as Chinese Pandas...

    "Isolation" can only work with respect to a branch that got isolated. Again, that can happen only if a change (system perturbation) occurs within the boundary of isolation. Even then, major genetic changes would be rare for higher level (complex) specis. For example, meat eating humans have not produced a different saliva chemistry (like canine family) than vegetarian groups.

    There may be other factors at work here that people are attempting to simplify like predicting weather...

    Just my two cents...
     
  8. Counterbalance Registered Senior Member

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    373
    Until the genetics enthusiasts arrive...

    Eflex, are we talking about genetic drift? The frequency of some specific alleles may change drastically (by chance) in small populations. And if the gametes of only a few individuals form the next generation, the alleles they carry may (again by chance) not be representative of the parent population. So, any number of small isolated populations may indeed differ greatly because of the “genetic drift.” Two primary causes of genetic drift are ‘founder effects’ and ‘bottlenecks.’

    With founder effects, rare alleles in the source population may make up a significant portion of the new (isolated) population’s genetic endowment. It’s thought that some organisms on the Hawaiian and the Galapagos islands were derived from one or a few founders. The same can be seen in isolated human populations where a group is dominated by genetic features characteristic of their “founder.”

    The bottleneck effect can result for groups cut off from their source population by sudden natural catastrophes or just from progressive changes. The survivors, then isolated, have a random genetic sample of the original population and are restricted in genetic variability. Cheetahs would be an example. A low genetic diversity is thought to lower their resistance to diseases.

    Sewell Wright‘s “Shifting Balance Theory“ suggests that random exploration will eventually lead to adaptive improvement. (May be what kmguru is refering to.) In other words, that “genetic drift continually perturbs the balance of alleles contributing to fitness, disturbances which allow different selective combinations to be tested by selection.”

    So, isolated groups can evolve with interesting characteristics/abilities that will aid their survival. Significant changes? In terms of changes that may strongly distinguish one isolated group from another, yes. And while I’m certainly no expert on the subject, it’s reasonable to theorize that the offspring of human colonists on Mars would go through at least some adaptive changes over time. Perhaps they’d develop a better metabolism; better ways to adapt to temperature extremes.

    At any rate, and as far as I know, a wide-spread mixing of different “ethnicities” is likely to increase genetic diversity.

    ~~~

    Counterbalance
     
  9. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    I'm thinking that you might compare a population of, say a million humans and a population of 5 humans. If it rains, the 5 humans will probably go into their cave and keep dry and warm. Will you be able to notice that in a population of a million humans? What if you make such a comparison over many years, many rains? Five humans going into a cave enarly every time it rains. Or some indeterminate oprrtion of one million humans maybe going into a cave when it rains. Clearly easier to determine behaviours and results in the smaller population.
     
  10. James R Just this guy, you know? Staff Member

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    Every time two humans breed, their genes are mixed. Over time, if two groups of humans interbreed, the mix of genes tends to be similar in all of them. On the other hand, if the two groups do not interbreed, random mutations and copying errors can develop in one group but not the other, so the two groups can end up with quite different characteristics. Isolation of one group from another reduces the chances of interbreeding.

    This has no implications on inter-racial breeding, since the concept of race has no genetic basis. The variation between any two individuals of a single race is, on average, greater than the variation between average members of two different races.
     
  11. Counterbalance Registered Senior Member

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    373
    Mornin’ James...

    Your post got me to thinking about the concept of “race.”

    (from Webster’s)

    1. A local geographic or global human population distinguished as a more or less distinct group by genetically transmitted physical characteristics.
    2. Humanity as a whole.
    3. A group of people united or classified together on the basis of common history, nationality, or geographic distribution (the Spanish race)
    4. aA genealogical line: LINEAGE.
    5. biol. An animal or plant population that differs from others of the same species in the frequency of hereditary traits: SUBSPECIES. b A breed or strain, as of domestic animals.
    6. A characteristic quality, as the flavor of a wine.

    For all of that, you are correct. Most current theories would support your assertions. (and your clarifications are appreciated as I had no intentions of misleading anyone)

    With respect to evolution, and variations in physical traits, what may be typically considered as “differences” between human “races” are thought to be less distinct than they were in the past. We’re becoming a homogenous blend, and in in the most obvious senses, presumably will continue like this as more blending of the ethnicities takes place.

    As is typical with me however, I’m guilty of always being aware that we have at best a limited understanding of what all has or could occur where evolution is concerned. (Assumption resistance; a lifelong occupation) I tend to think of possible exceptions that could develop due to pure randomness; unexpected environmental or cultural pressures, rather than a stable proportion of genotypes unaltered by meiosis or sexual reproduction.

    So while Migration and selection (thought to be prime factors in changing the frequency of some alleles), produce variation patterns that seemingly correlate with geographical distributions, these forces and their influences may differ greatly on any given group, causing more rapid divergence for some groups, or possibly creating subtleties in genetic variations that aren’t necessarily easy to detect -- or if they have been, their evolutionary role potentials aren’t easy to categorize. Isolating barriers aren’t always obvious either. I think there’s much that we’ve yet to comprehend about that which could promote or suppress genetic variation. Thus, I’ve yet to be convinced that we can be certain how important or influential (or not) the changes or types of variations actually are, and have consistently wondered about “dark horse“ genes that could emerge and become dominant due to present though overlooked ‘causes.’

    Considering what we do know, as well as all that we don’t, I’m still content to think it quite possible, even likely, that genetic variations of some types will increase as more humans (of any race) interbreed. Comes with the territory of being a “counterbalance” --leaving open doors of possibility-- because I see no reason to close them. (And it’s also a-ok with me if more evidence generated from further evolutionary progress should ultimately prove me wrong.) It’s the awareness of how advantageous it often is to keep an eye on the bigger (or sometimes smaller) picture that supports my conclusion. Despite the reasoning behind the general acceptance of some popular theories, in some instances I really don’t know of any reason to outright dismiss some possibilities, so I don‘t.

    Not that ANY of this will help to answer Eflex’s original questions,

    Please Register or Log in to view the hidden image!

    , but rather than confuse anyone further I thought I‘d offer some clarification of my own.
    ~~~

    Thx,

    Counterbalance
     
  12. Eflex tha Vybe Scientist Registered Senior Member

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    agreed.
    Homo Sapien is ONE species , one race

    However, Ethnicities DO exist.
    Which brings me back to my original question.......
     
  13. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    Are you trying to say that we and neanderthals were genetically the same? Let's have a look at something. Skin colour is determined primarily by our genes, yes? My skin is very pale. Someone with African ancestry for example may have very dark skin. These are based on genetic differences. Whether you refer to these groups of people as races or tribes or whatever, the fact is we are genetically different. People in different parts of the world have different skin colours, skeletal features, even difefrent glands in some cases (referring to a certain village in Italy I think where peopole don't have sweat glands, as an example). The fact is people are different.
     
  14. James R Just this guy, you know? Staff Member

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    Adam,

    Take 3 people: Yourself A (I assume a white anglo-saxon), and two black Africans B and C.

    Which pair will share more genes in common? (A and B) or (B and C)?

    The answer is: there is no way we can know by looking at them. You may be genetically more similar to B than C is to B.
     
  15. paulsamuel Registered Senior Member

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    882
    on race

    Race, as a biological term, is antiquated and is not used much by us (biologists) anymore.

    There is certainly population structure in humans, and geographic populations (once considered races) are genetically distinguishable.

    The causes and loss of genetic variability have been extensively studied. Your statement,

    "I think there’s much that we’ve yet to comprehend about that which could promote or suppress genetic variation,"

    is a gross overstatement.

    Neanderthals are (were) the same species as us, but are of a different subspecies, and the only humans that can be biologically considered a separate "race." There is however evidence of genetic mixing between Neanderthals and modern man (we did co-exist).

    Finally, interbreeding between genetically distinct human populations can only decrease genetic variation, not increase it. It's called homogenization.
     
  16. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    Race, geographic population, the terms change with social and political attitudes, but the reality remains: people ARE different. Do you know what happens in post-mortems when bodies are too deteriorated to be esily identified? Out come the big books of human traits, which can assist in identification based on these diferences: yep, racial profiling. It's done every day, all around the world, for solving murders and such. Why? People are different.

    As for Neanderthals and modern man interbreeding, yes, I recall that little girl dug up in Spain I think, who showed signs of both species or sub-species.

    JamesR: I am not Anglo-Saxon. The term anglo-saxon has for years been inappropriately used to describe ALL white Europeans. However, Anglo-Saxons are ONLY those people who are Angles or Saxons, those being people from two specific areas of Germany, later used to describe the invaders from those areas who kicked arse in Britain for a while. I am neither German nor British, although my ancestors were German (I have no idea which part of Germany, so I can't say they were Angles or Saxons). In short, calling all white Europeans Anglo-Saxon is as accurate as calling all Asians Yue.
     
  17. James R Just this guy, you know? Staff Member

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    Anglo-saxon, caucasian, whatever. Pick the term that suits you. I was just using it as an example. My point about genetic diversity stands.
     
  18. Eflex tha Vybe Scientist Registered Senior Member

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    Re: on race

    Race is a SOCIAL CONSTRUCT and it has no genetic/biological basis.

    If you guys want to argue this point.
    Go to

    http://www.sciforums.com/t6925/s/thread.html



    can you elaborate on this point please?
    I'm a little confused.
     
  19. Counterbalance Registered Senior Member

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    paulsamuel wrote:

    I think I understand why you'd believe this, and even why you'd feel strongly enough about it to make the point. However, and as I wrote above:

    Because I think it would be unjustifiably arrogant of any scientist to do so. We only know what we know. And for all that we do know, new discoveries, many relative to the human genome, are being made everyday. All that we've already learned about Evolution will continue to be tested, and in my opinion, should be tested. Not for the sake of disproving particularly, but for the sake of improving our understanding.

    We won't learn much or as well if we don't "listen." And we can't be listening if we've refused to hear.

    As far as scientists and those interested in this science know, you and James are correct.

    As far as I know... "I think there’s much that we’ve yet to comprehend about that which could promote or suppress genetic variation." And I look forward to learning all that may be revealed over time.

    ~~~

    thx,

    Counterbalance

    ~~~

    Eflex, look up the "Hardy-Weinberg principle, " "Hardy-Weinberg equilibrium," and "Hardy-Weinberg equation." That should make it all much clearer.

    Good luck.
     
  20. Northwind Master of Anvils Registered Senior Member

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    Isolation does indeed create greater diversity within a species. Examples of this can be found in Darwin's own studies of the Galapagos islands, which had such great diversity in sub-species between the various islands (notably in iguanas). However, diversity of traits does not in and of itself equal greater evolution. A small group that is isolated and therefore develops traits significantly different from those from its parent species is usually over-specialized to the environment that encouraged said traits, and is therefore less adaptable. Less adaptability is an evolutionary dead end and can lead to quick extinction if the environment changes.
     
  21. Eflex tha Vybe Scientist Registered Senior Member

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    THANK YOU.
    I'm beggining to understand now.
     
  22. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    I recall in The Naked Ape Desmond Morris refers to small, isolated groups such as isolated tribes in undeveloped parts of the world as "stultified" and evolutionary dead-ends.
     
  23. paulsamuel Registered Senior Member

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    882
    Re: on race

     
    Last edited: May 11, 2002

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