End of the World: Adam and Eve Scenario

[thorgold]

While brushing off some of my Stephen King books, I came across "The Stand." The whole post-apocalyptic theme sparked a train of thought in my mind that led to the "Adam and Eve" scenario of the apocalypse: one male and one woman are all that's left of the human population. They feel obligated to repopulate human society, on the grounds as they're the last ones on earth to do so.

I raised the question "Is that right?" Is it acceptable to feel obligated to repopulate the earth? To me, it seems, that bringing children into a post-apocalyptic world would be quite cruel, in the short and long term. Short term, children born would be brought into a collapsing world - we can assume that our infrastructure is gone, or unusable. Furthermore, with our numbers bottlenecked to two individuals, genetic degeneration would be unpreventable. Not only would newcomers to the world be both physically and mentally burdened throughout their lives, but over time things would just get worse as genetic diseases became more pronounced.

On the other hand, there is the noble thought of maintaining the race, as well as the whole concept of life having as many rich joys as hardships. It's a moral dillema as much as it is a physical one.

Thoughts, comments, consternations?

[mmmcannibalism]

My stark egoism says they should do what they think makes their lives better.

edit--actually

Its not as if your preventing suffering, its just going to shift to the next intelligent species to develop.

[PeterCai]

yeah, 2 people aren't going to be able to do crap. humanity is extinct at that point, so they aren't obligated to do anything.

http://en.wikipedia.org/wiki/Small_population_size

[Izawwlgood]

I for one would happily live on an island as a fuzzy seal-human.

[Iulus Cofield]

I also immediately thought of Galapagos.

[HungryHobo]

genetically humanity would be fairly screwed but we know from studies of the genome that there have been bottlenecks before when humanity was almost wiped out and we were down to perhaps a few thousand individuals and if they'd taken the same view that it was wrong to bring kids into a post apocalyptic world then we wouldn't be here.

There is the issue of bringing kids into a world where their only possible partners are their own brothers and sisters which is really messed up.

On the academic note when it comes to saving the species if you're willing to accept a fairly horrific rate of genetic diseases and non-viable births what's the utter minimum numbers you need to have in a species for bare survival?

[Izawwlgood]

On the academic note when it comes to saving the species if you're willing to accept a fairly horrific rate of genetic diseases and non-viable births what's the utter minimum numbers you need to have in a species for bare survival?

I've heard a bunch of numbers thrown around for questions like this, and the range is anywhere from 20 to 500. The important thing to realize is that humans are already very very inbred, and that stems from a bottleneck event that brought us to approximately 20,000 humans.

One good way to think about it is for a while, the amount of genetic variability and diversity will only be x, where x is the number of humans at the bottleneck. Some species could bounce back from narrow bottlenecks, like I think the Black Footed Ferret got down to ~18 individuals and now numbers in the thousands again, and some species of Gazelle was down to about 30 members and bounced back, but it's pretty bad news for the group to be in a situation like that. Better hope next seasons flu isn't particularly nasty to Fred, because you better believe it'll screw everyone as well.

[nitePhyyre]

On the academic note when it comes to saving the species if you're willing to accept a fairly horrific rate of genetic diseases and non-viable births what's the utter minimum numbers you need to have in a species for bare survival?

It depends on if you plan to plan who sleep with who and get rid of the monogamy thing we have going on, or if breeding would be as haphazard as it is today.

[firechicago]

I'm a little nervous about telling someone, even a hypothetical someone, that their life is not worth living and it would be better for them not to have been born. Obviously some of this depends on the form of the apocalypse that occurs, but I have a hard time seeing how the lifestyle of your Adam and Eve and their children would be any worse than the lifestyle enjoyed by our hunter-gatherer ancestors circa 100,000 years ago. Are you saying that their lives were not worth living?

[Izawwlgood]

I feel like there's a wealth of literature we can discuss that addresses these very questions. Anyone read The Road by Cormac McCarthy (Or see the movie)?

What would you do in his position?

What about Childhoods End by Clarke? What would you do if you were the last human being on the planet?

[omgryebread]

Are you saying that their lives were not worth living?

That is (...was) up to them to decide. I don't think I'd like it though. Wouldn't go for it. Wouldn't want to raise kids into it.

[CorruptUser]

Well, I heard somewhere you only need 36 people for a "healthy" colony; 4 men and 32 women, which would provide enough genetic distance to avoid marrying anyone closer than 2nd cousin. The reason for 8x as many women as men is that, well, men are less useful than women when it comes to re-population, so you get more mileage from 32 women and 4 men than 18 men and 18 women.

[mmmcannibalism]

Well, I heard somewhere you only need 36 people for a "healthy" colony; 4 men and 32 women, which would provide enough genetic distance to avoid marrying anyone closer than 2nd cousin. The reason for 8x as many women as men is that, well, men are less useful than women when it comes to re-population, so you get more mileage from 32 women and 4 men than 18 men and 18 women.

Or so the male scientists say

[omgryebread]

Well, I heard somewhere you only need 36 people for a "healthy" colony; 4 men and 32 women, which would provide enough genetic distance to avoid marrying anyone closer than 2nd cousin. The reason for 8x as many women as men is that, well, men are less useful than women when it comes to re-population, so you get more mileage from 32 women and 4 men than 18 men and 18 women.

Makes sense. Men are not limited in the number of kids they can have. 1 man can provide the sperm for as many women as he can get it on with, whereas a women is limited to 1 at a time (except twins), and 9 months apart.

[Izawwlgood]

Well, I heard somewhere you only need 36 people for a "healthy" colony; 4 men and 32 women, which would provide enough genetic distance to avoid marrying anyone closer than 2nd cousin. The reason for 8x as many women as men is that, well, men are less useful than women when it comes to re-population, so you get more mileage from 32 women and 4 men than 18 men and 18 women.

I'm not sure that actually follows; you'd have lots of people, but you'd still effectively have four 'families'.

In any case, it's still effectively a founder effect, and even though 4 men and 32 women can produce more babies than 18 men and 18 women, you've just limited the diversity of the population severely by only having four men in the starter. For the sake of genetic diversity, you want 18 men and 18 women, and you want to produce as many combinations as possible.

I think?

[Iulus Cofield]

Makes sense to me. In either case, the first generations have 36 genetic lines, but with only four men, the second generation is already limited to four lines. In the third generation your down to either one or two lines and by the fourth you're definitely marrying cousins.

I think you'd need at least 128 people. That way you have 64 families and should be able to manage that people are never marrying anyone closer than an 8th cousin. And assuming both perfect genetic diversity of the first generation and ideal distribution of genes in each child, after 8 generations there would less than 1% shared genomes. Not that genetics really works like that, but 64/64 seems a lot more reasonable than 4/32.

[Роберт]

In any case, it's still effectively a founder effect, and even though 4 men and 32 women can produce more babies than 18 men and 18 women, you've just limited the diversity of the population severely by only having four men in the starter. For the sake of genetic diversity, you want 18 men and 18 women, and you want to produce as many combinations as possible.

I think?

How are you going to effectively colonize planets with that thinking? Didn't you watch Dr. Strangelove?

Clearly, the need for genetic diversity should be considered, but you are going to want a higher percentage of women.

[Izawwlgood]

Personally, I'm going to effectively colonize planets by bringing thousands upon thousands of people to them, and allowing a continual influx of immigrants. I'll probably also bring a few million frozen embryos to be decanted and vat grown when the time is right.

Clearly, the need for genetic diversity should be considered, but you are going to want a higher percentage of women.

Except when you remember that the name of the game isn't necessarily 'make lots of babies!' but 'prevent babies from having sex with their relatives'. Yes, we know that a single man can make more babies in a population of many women than a single woman can in a population of many men. The thing you forget is that men contribute to genetic diversity just as well as women do.

[Iulus Cofield]

And, even with exclusive monogamy and slow reproduction rates, human populations still grow exponentially. I think the more women than men ratio is more important when you need to quickly rebuild your population, such as between Matrices or after a nuclear holocaust where every day is Lost Knowledge Getting Loster Day.

[firechicago]

Except when you remember that the name of the game isn't necessarily 'make lots of babies!' but 'prevent babies from having sex with their relatives'. Yes, we know that a single man can make more babies in a population of many women than a single woman can in a population of many men. The thing you forget is that men contribute to genetic diversity just as well as women do.

Actually the name of the game is balancing both. If you're trying to repopulate the world from a small population, you need to worry about genetic diversity, but you also need to worry about your entire seed population getting wiped out by one freak accident or simple bad luck. One way to do that is to make sure you reproduce as much as possible as quickly as possible. So while an 8:1 male to female ratio might not be optimal, I doubt the actual optimal ratio is going to be 1:1.

[Iulus Cofield]

Yeah, but the main danger with that is unavoidable in the first generations anyway. With 128 people, 112 of them being women, and each woman having 8 children, you're already at 896. Assuming half of them are women who each have 8 children, you're at 3548 and large enough to disperse in sufficient numbers to have independent communities. This conveniently ignores child mortality rates.

Also, keep in mind that if you make your female population into baby factories to drive population growth, men are going to have to do most of the labor in your group. You just can't expect a pregnant woman to farm very much. So each man is going to need to be able to reasonably support all of his partners and children for several consecutive years.

[Роберт]

The thing you forget is that men contribute to genetic diversity just as well as women do.

I am not forgetting that at all. I said it should be considered. Perhaps Dr. Strangelove's ratio was off when they said ten women per man. But it would make sense for it to be two women per man.

Men have a monopoly on Y chromosomes, and women have a monopoly on mitochondrial DNA.

So with 36 as an example of the number of people you're going to start with. Clearly, 35 men and one woman would be a bad idea. In fact, I believe we've established that the maximum number of men desired would be 50%. But is that really ideal? Why not 12 men and 24 women? I'm assuming you'd want marriages to keep STDs from wiping out the herd. I think it's obvious the 1 man and 35 women would be bad, or 2:34, 3:33, 4:32. But I think you would want to seriously consider 9:27 and 12:24 as well as 16:16.

I don't think it's feasible to colonize by sending thousands.

@ Iulus Cofield: you're also conveniently ignoring dying in childbirth or pregnancy complications. Which is going to be a factor if you have a limited set of people.

[Iulus Cofield]

Very true, but we're ignoring a lot of potential problems here. We should restrict ourselves to things that will definitely be issues, like genetic diversity and food production.

[Роберт]

Also, keep in mind that if you make your female population into baby factories to drive population growth, men are going to have to do most of the labor in your group.

Pun not intended I assume. But yes, men are incapable of growing a fetus to viability, so it make sense that would go to the women and the men would have to take on a different responsibility.

8 children per woman seems rather high. I think in the first generation you'd be lucky if you average 2 children reaching child-bearing age per woman. The second generation will probably fair better, but I imagine the women will have to be breastfeeding (there is no formula factory in operation) which will enforce a distance between kids. Assuming they start at 16 and go until 32, that's only 16 years. Accounting for child mortality, death in childbirth, infertility, etc., you'd be lucky if you got 4 per woman to reach fertility themselves..

[Iulus Cofield]

You're complicating things! Complex things are hard!

[Izawwlgood]

Men have a monopoly on Y chromosomes, and women have a monopoly on mitochondrial DNA.

It's not so much that the Y chromosome is useful (it really isn't) or that mitochondrial DNA MUST be diverse (it doesn't have to be), it's that ~half your genetic diversity is coming from your paternal side, and ~half from your maternal side. If you create a population, and have a 1:1 ratio of male:female, you have approx half your diversity in one side of the reproductive pool, and half in the other.
Skew that, and you load your initial diversity in a population that can't intermingle it.

I don't think it's feasible to colonize by sending thousands.

We're running with a lot of assumptions here; I'm assuming that because interstellar travel is possible, so is shipping lots of people. If we're getting back to the concept of smallest number to colonize, I still think that long term, total number is less important than maximally diversified founder pool. In the short run, it may be handy to have a extra people, but 6-8 generations later when recessive mutations are cropping up like mad, you'll be wishing you had grown slower from a wider base.

Just look at the Amish; they're significantly larger than 40 some odd people, and have enormous problems with mental retardation due to inbreeding.

[LaserGuy]

And, even with exclusive monogamy and slow reproduction rates, human populations still grow exponentially. I think the more women than men ratio is more important when you need to quickly rebuild your population, such as between Matrices or after a nuclear holocaust where every day is Lost Knowledge Getting Loster Day.

Wouldn't monogamy actually be a really bad idea in this instance? If your goal was to maximize genetic variability, it seems to me that you'd be better off having each child coming from a different father. Monogamy would tend to create more bottlenecks, I would think.

[Izawwlgood]

It goes both ways; all monogamy and you limit your diversity, no monogamy, and everyone ends up being related to everyone quicker.

[Роберт]

Men have a monopoly on Y chromosomes, and women have a monopoly on mitochondrial DNA.

It's not so much that the Y chromosome is useful (it really isn't) or that mitochondrial DNA MUST be diverse (it doesn't have to be), it's that ~half your genetic diversity is coming from your paternal side, and ~half from your maternal side. If you create a population, and have a 1:1 ratio of male:female, you have approx half your diversity in one side of the reproductive pool, and half in the other.

Once you get a few generations down. (Which if we're starting with at least 8 males mixing close relatives won't be forced for until a few generations down) the genetic material is going to be swished about enough that it won't matter. You get 50% of your genetic material from your mom, and 50% from your dad, but it is NOT 25% from each grandparent.

Generation 0 obviously will have no genetic issues. Assuming reproduction is in married groups, generation 1 will just have to avoid everyone with the same father, which, with 9 "Adams" in my 9:27 example, will leave them with about 8/9ths of the population available. Generation 2 will have quite a few limitations, but should still be easily able to find 100% none-relatives. Generation 3 may start to have problems with sharing great-fathers, but you're not even first cousins at that point.

The main thing I'm worried about by limiting men is the Y chromosome, but if you are doing marriage, a 18:18 one man, one woman thing is much more likely to end up with a dead end of males (couple has all girls, couple has only one boy, said boy has all girls, etc) than if you do 9:27 or 12:24. I think 12:24 would be ideal, actually.

I'm also potentially worried about sexually transmitted diseases that cause fertility issues. I don't want monogamy for generation 0, but I don't want free-love/open relationships either. I want polygyny, and the participants faithful within the marriage. For generations 1 and 2, I want monogamy and polygyny or polyandry as needed so that everyone gets married with no genetic overlap.

I'm not sure what to do with non-heteros, but I'd like their genetic material to still contribute to the pool. I guess ideally a pair of lesbians or bi women could "marry" a man and could both accept his genetic material in what ever way is most acceptable to them... any asexuals etc would hopefully participate in a similar manner until the population is sufficiently large.

[LaserGuy]

I'm also potentially worried about sexually transmitted diseases that cause fertility issues. I don't want monogamy for generation 0, but I don't want free-love/open relationships either. I want polygyny, and the participants faithful within the marriage. For generations 1 and 2, I want monogamy and polygyny or polyandry as needed so that everyone gets married with no genetic overlap.

I'm not sure that STDs would be any more of a problem than the multitude of other possible communicable diseases that could wipe out such a small group. As long as nobody has an STD in the initial population, I would think that the overall risk would be pretty low.

[Izawwlgood]

But again, you're still limiting the diversity you start with. If 3-4 generations later you can start inbreeding without fearing closer than second cousin relations, that's fine, but you're still starting with lesser initial diversity. The likelihood of severe issues cropping up may be small, but you're still basically guaranteeing that recessive issues will crop up shortly.
So it still depends on what you're after; if you want a maximally sized colony as soon as possible, then do it your way. If you want to maximize the long term survivability of your colony, do it mine.

Of course, more people means more hands on deck in an emergency, so sure, there are a couple ways to address this. Just think of a virus ripping through a population of cousins, vs a virus ripping it's way through a genetically dissimilar population.

[Роберт]

But again, you're still limiting the diversity you start with. If 3-4 generations later you can start inbreeding without fearing closer than second cousin relations, that's fine, but you're still starting with lesser initial diversity.

Please explain to me how you're limiting the diversity. I'm an engineer and I've taken biology in college, so I have a decent understanding of genetics.

[LaserGuy]

But again, you're still limiting the diversity you start with. If 3-4 generations later you can start inbreeding without fearing closer than second cousin relations, that's fine, but you're still starting with lesser initial diversity. The likelihood of severe issues cropping up may be small, but you're still basically guaranteeing that recessive issues will crop up shortly.
So it still depends on what you're after; if you want a maximally sized colony as soon as possible, then do it your way. If you want to maximize the long term survivability of your colony, do it mine.

Of course, more people means more hands on deck in an emergency, so sure, there are a couple ways to address this. Just think of a virus ripping through a population of cousins, vs a virus ripping it's way through a genetically dissimilar population.

Regardless of which situation you choose, genetic variability is the same in the long term, because it is limited by the number of members initially. Convergence would presumably be that each individual will have a 1/n "share" from each of the founding members. If the number of founding members is sufficiently small, you will end up with recessive problems regardless of what breeding strategy you employ.

[Diadem]

A much more interesting question is: If we're down to these 36 individuals (in whatever ratio of men to women), does any of the people in that group still have the right to say: "Nah, I don't like children, sorry, I won't be getting any". Or would reproduction become a moral imperative?

[mmmcannibalism]

A much more interesting question is: If we're down to these 36 individuals (in whatever ratio of men to women), does any of the people in that group still have the right to say: "Nah, I don't like children, sorry, I won't be getting any". Or would reproduction become a moral imperative?

Is the continuation of the human race a moral imperative?

[Izawwlgood]

Is it relevant when discussing genetic diversity or genetics?

But for the sake of discussion, in the event of finding yourself in such a position, Diadem, what would you do? What about if you were born into it?

[mmmcannibalism]

Is it relevant when discussing genetic diversity or genetics?

But for the sake of discussion, in the event of finding yourself in such a position, Diadem, what would you do? What about if you were born into it?

Well the OP was about the morality of what should be done, so genetics is just a part of that.

[Iulus Cofield]

Oh my, we got fairly down a tangent and I didn't realize it at all.

In the situation described by OP, I would try to repopulate the earth. The chance of succeeding is simply too low and fraught with many, many problems. Sometimes you just have to accept that your species' time has run out.

[CorruptUser]

Scientists inbreed mice all the time, to get specific phenotypes. Take 2 mice, breed them. Then take 2 of their children, and breed again. After about 10 generations, you end up with mice that are all virtually clones. But most importantly, they are viable, as the deformed mice are not chosen for continued breeding. Usually; sometimes they are, because scientists are curious about how deformities develop.

Sure, you WILL have to deal with nasty results of inbreeding for a few generations, but after that, the result is a species that is with limited or nonexistent recessive disorders. That and a population incredibly unable to adapt to disease and/or change in conditions, but we humans are known more for making the world adapt to us rather than us to it. At least in our thinking. So, yes, it is very possible to continue the species with just 2 people.

[Iulus Cofield]

Unless one of those two people has Huntington's disease. You can inbreed mice quite well because they carefully select the first generation. I think the premise here doesn't include a pre-apocalypse eugenics plan.