Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Long term genetic outcome of one time very harsh unnatural selection on humans

  1. Nov 15, 2012 #1
    A few topics ago I asked about possibilities concerning maintaining contemporary tech level with seriously reduced population. Now I will ask a question for the same story.

    There is a standard, generic incoming doom. The general population is already roughly aware how nasty the situation is. (with both people overreacting and underestimating the problem)

    There is an Organization that can save 0.5 - 1 mln people (with soft SF means). It is effectively flooded with prospective applicants who want to be taken.

    - a few people (like some politician kids) has to be taken just as a racket paid to politicians of great powers to make them cooperative, however their share in the gene pool is relatively minor (less than 1%);
    - there is clearly a need for experts necessary for survival, (round 10%) but even among them one can be a bit picky;
    - for the rest of people there are at least 100 candidates per place; (you don't ask for any special skills in particular)
    - the Organization don't want to choose the rest of lucky ones at random, but want to apply some rational mechanism of selection - they want people who are young, healthy, fit, intelligent, educated and not making troubles; (unofficially also: easy to govern)
    - the Organization, if given a chance, would like to weed out genetic problems or transmittable diseases; (nothing personal, but if they have two similar people, and have to chose one, the one with hereditary problems is left)
    - the Organization is neither politically correct, nor racist - it would not disqualify anyone merely for his race, nor would it care at all for keeping any ethnic quotas;
    - the test have to be done rather quickly (a month or two, tops) and can not be prohibitively expensive;
    - asking for showing any medical history or medical history of relatives is possible, however, people would be desperate so if only asked would gladly admit being offspring of people living as long as Methuselah or as fit as Heracles. (not mentioning that a few might even try to forge documents confirming such claims);
    - there is no special preference for countries as such, but as you know when there are some life boats filled it's always: women, children and first class passengers, so selection would be presumably somewhat biased in favour of more developed countries.

    OK, so two question:
    1) Which tests should be applied aimed at which genetic (or transmittable) diseases? Should genetic tests be run or maybe rather analysing phenotype would be easier?

    2) What should be long term outcome in next generations? (which diseases would be eliminated / reduced? Would there be any side effects?)
  2. jcsd
  3. Nov 16, 2012 #2
    Based on the book "Emperor of all maladies: The biography of cancer", I can say that you could test for some cancers (obviously), but that's nothing high on the public's radar. Like some eye cancer in some South American families. To the best of my knowledge, we don't know have any knowledge pertaining to major diseases that could connect them to any specific genes (if that makes sense). You could probably sort out hemophilia. But, as wikipedia http://en.wikipedia.org/wiki/Genetic_disorder points out, genetic disorders affect one out of several thousand, so, even if the Organization chooses randomly it's not going to get many hereditary genetic disorders (if any).

    Also, I think I noticed an error:
    it should be 7 000 / 0.45-0.9 (-10%) (mln) = 8-15 000 people per place. Or I could be misunderstanding.
  4. Nov 17, 2012 #3
    I thought about a wider approach, for example:

    source: http://archpsyc.jamanetwork.com/article.aspx?articleid=210642

    Assuming that they would also try to exclude let's say people with mental problems (which partially have genetic causes), that should have lower prevalence in the next generation... Right? Or would the outcome be hardly noticeable? (not a rhetoric question, I'm quite curious for which diseases there should be a dramatic reduction, and where any outcome would be presumably below statistical significance)

    Your math is correct, however, there are a few factors (which maybe I haven't expressed explicitly enough) that would ruin it, like:
    -everything has to be done in hurry, so it's not worth the effort to look for people from many third world countries, where there would be poor medical documentation, on average not so well educated population, high HIV rate, annoying bureaucracy to deal with etc.;
    -7 billion people includes those who are ex. 65 years old;
    -not everyone would apply to be taken (distrust towards true aims of the Organization, not being convinced about the doom, not wanting to leave all his family behind).
  5. Nov 17, 2012 #4
    That clarifies the math point a bit, except then I don't know how you came up with 100 per place.

    Otherwise, I'm not knowledgeable enough, but I would suggest that disorders like your example aren't traceable to particular genes, so genetic analysis won't do any good. You'd have to rely on family history. I've got no idea how efficient that is.

    On the other hand, according to the Abnormal Psychology textbook I'm reading, I believe it's about 50% of US citizens that have a psychiatric disorder during their lifetime (I'm not sure where the data was, so I can't check for sure). You could filter them out, although there is a problem that you have most of creative intelligent people there, especially with various depressions. The textbook also suggests that for DSM-V they should adopt a scale approach, where most disorders are just exaggerations of normal traits to different degrees. That would sure make things complicated for gene-based filtering. (Not the fact of DSM-V being based around that, but the state of nature being like that).

    Another thing, when you're cutting your sample so drastically you're running into the risk of getting skewed statistics, as when you throw a coin 5 times as opposed to 500 (you simply can't get a 50/50 ratio in the first case). Which brings me to my point that you've got quite a bit of artistic license, considering our state of knowledge on the subject. So the Organization could conceivably find on its own a gene for some mental disorder, and get rid of it. Although I'm not sure what that would accomplish for the plot (I mean, more problems is better, right? :smile:). Alternatively, by selecting intelligent creative people they could unintentionally increase the prevalence of depression.
  6. Nov 17, 2012 #5
    Simply a ballpark figure.

    For story reasons I assume that only contemporary knowledge is used. So rather elimination based on family history.

    No, the plot is freakish enough even without any additional problems. (though some problems can be interesting for story reasons... ;) ) I rather tried to follow here the logical outcomes of such choices. I want to keep it here realistic. I don't want to exaggerate and reach a conclusion that if Australia used to be a penal colony in early XIXth century, then it should be lead by crime syndicates in early XXIst century. ;)

    To what extend depression and intelligence or creativity are indeed correlated? I mean I have merely anecdotal evidence for over representation of mental problems among artists, no hard evidence (except hearing rumours) for high IQ correlated with depression (not mentioning that I would be worried that higher diagnose rate could merely mean that brighter sad people are more likely to seek professional help) Do you have any data that support that? (I'm just curious, I'm not challenging that what you said)

    To be honest, if I was to show some negative consequences of overeager fighting with any genes that predispose people towards bad mood, I start to wonder whether it would end up with more optimistic people that are in US investment banking. ;)
  7. Nov 18, 2012 #6
    Okay, yeah, it also may be that intelligent middle-class women (according to that textbook) are the most likely to seek psychological help... But then, they are more likely to have psychiatric records, therefore the selection could be skewed against intelligent middle-class women. Although that would mean that the Organization's scientists are stupid.

    I'm pretty sure my resources on this subject are exhausted now, so good luck with your writing, Czcibor. :smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook