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Thread: Human survival.

  1. #1 Human survival. 
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    Has anybody here have any idea how few people would be required to sustain and even increase a population? I was thinking about polynesians finding remote pacific islands and inhabiting them and wondering what the minimum number might be. The internet is full of uneducated 'gestimates' - I'd like something a bit more accurate.


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    There is one example from history - Pitcairn's Island (Mutiny on the Bounty fame).


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    The Maori people here in New Zealand colonised an entire country, and grew to an estimated 250,000 in number over 600 years before Europeans arrived. Mitochondrial studies show they began with 200 women.
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    Easter Island would be another example. Starting population probably a few dozen and never getting over a few thousand over a thousand year period.
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    Well it looks like we survived with a starting population of about 2000. That is pretty slim pickings if you ask me and again that's why human genetic diversity is not what it should be today. But we survived.

    When humans faced extinction

    Humans may have come close to extinction about 70,000 years ago, according to the latest genetic research.

    Televisual representation of early Homo sapiens, BBC
    From just a few, six billion sprang
    The study suggests that at one point there may have been only 2,000 individuals alive as our species teetered on the brink.

    This means that, for a while, humanity was in a perilous state, vulnerable to disease, environmental disasters and conflict. If any of these factors had turned against us, we would not be here.

    The research also suggests that humans (Homo sapiens sapiens) made their first journey out of Africa as recently as 70,000 years ago.

    Complete article: BBC NEWS | Science/Nature | When humans faced extinction
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    Is this a matter of a minimum 'genetic variation' limit or a minimum skills limit? It's a question I'd like an answer to as well. In places of relative abundant resources that can be utilised with minimal skill or technology plus a bit of luck - no severe genetic disorders lurking in the genome that would impact the first generations - would one couple plus incest create a growing population?
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    I have heard of speculations that at one time in pre-history there were as little as 8000 humans left alive on the entire planet, and that humans almost died out.
    It is by will alone I set my mind in motion.
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    The research also suggests that humans (Homo sapiens sapiens) made their first journey out of Africa as recently as 70,000 years ago.
    That article was from 2003. I'm perfectly happy with the idea of near extinction whenever it might have been. But that 70000 years for the out of Africa movement seems a bit recent. There's some evidence accumulating since 2003 that Australia (and maybe China) had human inhabitants very close to 70000 years ago if not more. Couldn't find the item I had in mind on a quick Google Scholar search, but I'll keep an eye out or think up a new search term.
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    Adelady

    Human colonisation of Australia is normally considered to have happened between 45,000 and 60,000 years ago.
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    Yeah, I know. I had a recollection of something more ancient in the last 18 months or so. It's probably not even made it into a journal yet.
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    I'm not sure there really is a minimum number. If you have too few people there will be a lot of birth defects for a long time, but ultimately natural selection can filter some of that stuff out.

    At least that would make sense with a large enough family size. If the family size is too small then each generation might be producing too few children to beat the odds.
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    Quote Originally Posted by adelady View Post
    The research also suggests that humans (Homo sapiens sapiens) made their first journey out of Africa as recently as 70,000 years ago.
    That article was from 2003. I'm perfectly happy with the idea of near extinction whenever it might have been. But that 70000 years for the out of Africa movement seems a bit recent. There's some evidence accumulating since 2003 that Australia (and maybe China) had human inhabitants very close to 70000 years ago if not more. Couldn't find the item I had in mind on a quick Google Scholar search, but I'll keep an eye out or think up a new search term.

    Link
    ► Out of Africa 2 earlier and more complex than currently envisaged. ► Homosapiens likely exited Africa from 125 ka onwards rather than after 60 ka. ► H. sapiens dispersals from Africa likely from several donor populations. ► H. sapiens likely entered Asia several times and from several entry points. ► Inter-breeding likely between H. sapiens, Neanderthals and Denisovans.
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    Quote Originally Posted by kojax View Post
    I'm not sure there really is a minimum number. If you have too few people there will be a lot of birth defects for a long time, but ultimately natural selection can filter some of that stuff out.

    At least that would make sense with a large enough family size. If the family size is too small then each generation might be producing too few children to beat the odds.
    Some good Info in topic below. Another science forum for those of you who have led a sheltered life in this forum.

    Minimum viable human population
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    Quote Originally Posted by Home200 View Post
    Has anybody here have any idea how few people would be required to sustain and even increase a population? I was thinking about polynesians finding remote pacific islands and inhabiting them and wondering what the minimum number might be. The internet is full of uneducated 'gestimates' - I'd like something a bit more accurate.
    As you probably realize at a minimum it would take only one pregnant female to found a population. In reality food is not that easy to come by in most locations so usually such a founding population would require a minimum of a small group to provide the genetic diversity and the combined skills to find and prepare food while probably having to hunt and possibly to ward off animal predators and possible waring conquests and predations by their own or different human species. Because of the lack of variation of the genetics of certain islanders in the Americas and Polynesia, it is believed that some were probably originally founded by populations smaller than 40 individuals. Based upon such genetic analysis I think the best they can do is guesstimates. They cannot know for sure what new genetic influxes might have taken place before such populations could be studied.
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    Isnt this a question of probability?

    If you have one fertile man and one fertile woman, and if you set taboos aside, lets say their progeny interbreeds. You will have all sorts of problems, but is there really 0.00% chance that a thousand years later you dont have a population with some divergence (mutations etc), and a 100% chance that all will have been made extinct by genetic problems or a specific disease for which the entire population was vulnerable?

    Clearly the more diversity the better, thus, the more different people the better, and its even better if you have colonies in other environments outside earth(moon base, mars base, asteroid) which increases the long term odds of survival (in case an unforeseen event wipes out humans on earth).
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    Quote Originally Posted by icewendigo View Post
    Isnt this a question of probability?

    If you have one fertile man and one fertile woman, and if you set taboos aside, lets say their progeny interbreeds. You will have all sorts of problems, but is there really 0.00% chance that a thousand years later you dont have a population with some divergence (mutations etc), and a 100% chance that all will have been made extinct by genetic problems or a specific disease for which the entire population was vulnerable?

    Clearly the more diversity the better, thus, the more different people the better, and its even better if you have colonies in other environments outside earth(moon base, mars base, asteroid) which increases the long term odds of survival (in case an unforeseen event wipes out humans on earth).
    Most interbreeding is not problematic in the first generation, but progressively gets worse with each new generation after that as long as interbreeding continues. I can't remember where I read it, but the impression I have is the human race would never be able to produce a viable species from a single mated pair. We would cease to exist long before a 1000 years came around.
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    arKane, I doubt that "we would cease to exist"
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    We have an example here in New Zealand of a species that recovered, with all individuals descended from one mother. The Chatham Island Black Robin. At one point, just one fertile female was left, called "Old Blue". She was the mother of her entire species, which is now approaching 300 individuals and thriving under care by government conservation officers.
    Black Robin - Wikipedia, the free encyclopedia

    While this was a bird, and not human, it shows that it is possible for a severely inbred species to survive and grow.
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  20. #19  
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    Quote Originally Posted by Home200 View Post
    Has anybody here have any idea how few people would be required to sustain and even increase a population? I was thinking about polynesians finding remote pacific islands and inhabiting them and wondering what the minimum number might be. The internet is full of uneducated 'gestimates' - I'd like something a bit more accurate.
    Just a thought but providing they were capable of surviving, I mean having enough food etc.., would you really need more than a couple of families as a start for a whole community, we often see women having 12 or sometimes even more children in some countries, so provided you maintained high breeding rates and could always have enough food and fresh water then the population would surely be able to rapidly expand over even a just a few generations. Just think if even every 2 people can change to another 6 with each generation how quickly even only 2 families could repopulate a country.
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