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  1. #41
    River's Roommate carmencatalina's Avatar
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    Default Re: Genetic Diversity

    Finally, a topic on which I can speak intelligently!

    I'm a population geneticist, this is what I'm actually teaching this semester.

    As several people have pointed out, one of the questions is the relative proportions of males and females. Biologists use a term called "effective population size" to measure how much genetic diversity a population will likely maintain over time.

    For a population that has Nm males and Nf females (where Nm and Nf are integers representing the actual number of males and females), the effective population size is:

    Ne = 4*Nm*Nf/(Nm + Nf)

    So let's say that there are 20 women and 40 men aboard the Destiny.

    The effective population size is only: 4(20)(40)/(20+40) = 3200/60 = 53.33

    This is less than the actual population size of 60, because each new person receives 1/2 of his/her genes from a female and half from a male - the smaller number of females forms its own "bottleneck".

    This assumes everyone is equally likely to reproduce - the effective population size will be smaller if there are some individuals that reproduce more than others.

    But let's take an effective population size of about 50 as our estimate. Is that big enough to found a human population for the long term?

    It is if the founding population is genetically diverse enough, so that it is unlikely that any two people are carrying the same recessive deleterious mutations. We all have some recessive deleterious mutations - most of the time, the person with whom we reproduce has different ones, and then our offspring don't get 2 copies of a deleterious gene at the same locus (gene). That's why many (but not all) organisms avoid close inbreeding.

    The current theory of human population expansion out of Africa poses multiple small groups founding population in Europe and Asia. It is certainly likely that some of these groups had less than 100 breeding individuals. Could they have persisted without later influxes of people and genes from other groups?

    I think the answer is "maybe". Certainly, we have seen populations of other mammals survive bottlenecks much more severe than 50 breeding individuals.

    Goodbye and Good Travels, Destiny!

  2. #42
    Colonel knowles2's Avatar
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    Default Re: Genetic Diversity

    Rhinos are one species that have been bought back from very low numbers, some species as low as fifty I believe. An they are accepting to do the same with the last 7 remaining Northern White Rhino.
    But some mammals have got a natural resistance to inbreeding, cats for instant.
    carmencatalina may be you should give the SGU scenario as an assignment for your students to answer whether the population on destiny is viable or not.

  3. #43
    Colonel
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    Default Re: Genetic Diversity

    actually you don't need more than 60 people to start a civilisation. Of course, there must be more females than males, but it's fine to begin with less than 60 (56 to be more accurate). Some of descendants would be "slower" but you don't high numbers.

  4. #44
    River's Roommate carmencatalina's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by knowles2 View Post
    carmencatalina may be you should give the SGU scenario as an assignment for your students to answer whether the population on destiny is viable or not.
    I would need to make some assumption on the frequency of deleterious mutations in the initial Destiny population, and on how genetically related they are. If you throw in that information (that we don't have), you could do some fun calculations.

    Excellent idea for a homework problem!

    Goodbye and Good Travels, Destiny!

  5. #45
    Second Lieutenant Trinary's Avatar
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    Default Re: Genetic Diversity

    I believe in a single gene could mutated into different races if they spread into different geographical area in a planet or the variation how they live their life. The surrounding area most likely contribute how they evolve and adapt to the place they live in. It will resulting into a different skin color, shape of the eyes, their height and various other changes.

    For example, a number of a fat human race are now increasing around the world based on what and how they eat such as similar food menu and frequency. They're basically a new human race that evolve drive by the food they had consumed. They used to be abnormal, but now it was seem common a new born overweight baby taken these new evolved gene.

  6. #46
    First Lieutenant Starsaber's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by carmencatalina View Post
    ...
    {Good stuff}
    ...
    Thanks for the very informed answer. I'm a software engineer, not a biologist or statistician, so it was mostly idle speculation on my part.

    Another thing. Do the close matches for kidney transplants play into the genetic diversity much, or is that something different. Wouldn't have an impact on the first generation, since Brody and both potential donors were male, but I'm curious.

    Oh, and time to update your signature. Down to 3 new episodes left

  7. #47
    River's Roommate carmencatalina's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by Trinary View Post
    I believe in a single gene could mutated into different races if they spread into different geographical area in a planet or the variation how they live their life. The surrounding area most likely contribute how they evolve and adapt to the place they live in. It will resulting into a different skin color, shape of the eyes, their height and various other changes.

    For example, a number of a fat human race are now increasing around the world based on what and how they eat such as similar food menu and frequency. They're basically a new human race that evolve drive by the food they had consumed. They used to be abnormal, but now it was seem common a new born overweight baby taken these new evolved gene.
    Most of the traits you've mentioned here (skin color, weight, shape of eyes, height) are most definitely NOT caused by a single gene. They are all examples of what we call "quantitative" or "complex" traits - that are due to the actions of multiple genes AND environmental components.

    While you can definitely have mutations of single genes that affect these traits, the variation you see in our human population in these traits is NOT due to the action of a single gene.

    Goodbye and Good Travels, Destiny!

  8. #48
    First Lieutenant Starsaber's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by carmencatalina View Post
    ...
    {Good stuff}
    ...
    Thanks for the very informed answer. I'm a software engineer, not a biologist or statistician, so it was mostly idle speculation on my part.

    Another thing. Do the close matches for kidney transplants play into the genetic diversity much, or is that something different. Wouldn't have an impact on the first generation, since Brody and both potential donors were male, but I'm curious.

    Oh, and time to update your signature. Down to 3 new episodes left

  9. #49
    River's Roommate carmencatalina's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by Starsaber View Post
    Oh, and time to update your signature. Down to 3 new episodes left
    Thanks! Updated (sadly).

    Goodbye and Good Travels, Destiny!

  10. #50
    Second Lieutenant Trinary's Avatar
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    Default Re: Genetic Diversity

    I noticed there was 2 different height of human race in overall. Most of the south origins were shorter while the north origins were taller.

    What make of it? Atmospherics pressure? Gravity? or Magnetic poles configurations?

  11. #51
    Chief Master Sergeant
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    Default Re: Genetic Diversity

    Smaller tribes of people in other cultures have lasted fairly long with a small gene pool. Plus, most of the military personals have been selectively picked in a way that does eliminate certain genetic defects, so in terms of genetic problems, they may have little. If the south can survive for a greater part of 2 centuries, I'm not surprised the Destiny crew can survive longer.

  12. #52
    River's Roommate carmencatalina's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by Trinary View Post
    I noticed there was 2 different height of human race in overall. Most of the south origins were shorter while the north origins were taller.

    What make of it? Atmospherics pressure? Gravity? or Magnetic poles configurations?
    I don't think this is correct, there are certainly groups of humans that are overall shorter or taller, but there isn't a clear longitudinal gradient. You can look at the Inuit, who certainly live far towards the north pole, and see a people that are not very tall.

    Goodbye and Good Travels, Destiny!

  13. #53
    Major General
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    Default Re: Genetic Diversity

    Quote Originally Posted by D Toccs View Post
    Each one of those pairs would have to have at least 3 or 4 children. Each one of those children would have to be paired up with someone in an "arranged marriage" in order to keep maximum diversity and avoid the same families crossbreeding more then needed.

    In short, the society for at least the first few generations would be centered around the gene pool.
    You would be assigned a sexual partner (the only one you'd be allowed to have) and your duty would be to produce as many children with that partner as possible. Your children upon coming of age would then be assigned their own partners and so on.

    Given human nature, such a structured society would be difficult to maintain.
    Which to me, might not be too far off what might have happened.. Especially since most were US and therefore were raise with the history of the pilgrms, who in some parts did just that.


    My problem is that 2000 years did not make an advanced society like that quite believable. Maybe they went back farther, like 20,000 years or something.

    They were raised with the knowledge the crew had.. which is pretty important. The only 2 limiters would be what resources they had, and what was passed on.

    If the first wave of women pump out 10 kids per with several men it wouldn't be an issue. Star Trek did a show on this very topic. Ironically enough on the startrek episode, an extended liberty would have injected (quite literally) a whole lot of Enterprise genetic material into the cloner gene pool.
    There was also a film on the Scifi channel, iirc where a virus (man made) was released by baddies trying to steal it, and the only way to stay safe against it was be in the polar cap. So the US antartic site was good.. Each woman there had to do a 'lottery' for the men to see whom would be their birther for that 'season'...

    May be they did. We do not know how long they spent on the planet before they cut off.

    An it might be that they cannibalise there most advance pieces of technology to keep the power generators and radio communication equipment going.
    Plus maybe they didn't have the natural resources to do some of that..

  14. #54
    First Lieutenant D Toccs's Avatar
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    Default Re: Genetic Diversity

    Another problem, is that the group that split away to become the Futurans did so in The original Destiny crew's lifetimes. I can't imagine after such a schism that there would be much interbreeding between the two rival groups.

    So while there is a chance that the original group could form a stable population. That original group was split in half very early on, effectively halving the gene pool for both factions.

    I just can't see how it could work given that situation.

  15. #55
    Major General
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    Default Re: Genetic Diversity

    Well, if i have 2 kids a year, every 3 yrs, i can have a lot of kids in 40 years..

  16. #56
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    Default Re: Genetic Diversity

    Quote Originally Posted by D Toccs View Post
    Another problem, is that the group that split away to become the Futurans did so in The original Destiny crew's lifetimes. I can't imagine after such a schism that there would be much interbreeding between the two rival groups.

    So while there is a chance that the original group could form a stable population. That original group was split in half very early on, effectively halving the gene pool for both factions.

    I just can't see how it could work given that situation.
    From Young's apparent age it was 30 or 40 years. Long enough to have two more generations of people.

  17. #57
    First Lieutenant D Toccs's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by BadOnion View Post
    From Young's apparent age it was 30 or 40 years. Long enough to have two more generations of people.
    It would still reduce the gene pool of each side down to smaller then the original crew.

  18. #58
    Lieutenant General thekillman's Avatar
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    Default Re: Genetic Diversity

    i believe the Futurans only really founded a nation much, much later.


    it isn't really clear and that kino footage doesn't actually show them leaving, just considering leaving

  19. #59
    First Lieutenant D Toccs's Avatar
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    Default Re: Genetic Diversity

    Quote Originally Posted by thekillman View Post
    i believe the Futurans only really founded a nation much, much later.
    We know that Brody named Futura so the original crew must have still been alive.

  20. #60
    Colonel knowles2's Avatar
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    Default Re: Genetic Diversity

    We still do not know how bad relations were between the two groups. I guesting this will be explored sooner or latter or may be that was a season 3 episode.
    For all we know they may have spent centuries being friendly to each other, yes a rivalry in interpretation of history but still friendly.
    An still trading and interbreeding for generations together.

    I guest we will fine out more next episode.

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