“Suppose atomic bombs had reduced the population of the world to one brother and one sister, should they let the human race die out? I do not know the answer, but I do not think it can be in the affirmative merely on the ground that incest is wicked.”
Bertrand may not know, but I reckon you’ve got an opinion. When Russell wrote that it was 1954 and bombs were the big menace, but these days I doubt anyone thinks they will wipe out almost everyone. So instead, let’s say an extremely deadly virus wipes out everyone except a brother and sister who are immune.
Should humanity die with them or carry on?
Oh, and for the smartarses the spermbanks and frozen eggs have been without power for too long, so no joy there. However to make things less squicky artificial insemination techniques are well known these days.
Two people are not a big enough gene pool, brother-or-sister or not: humanity is doomed. I understand there are some places (Netherlands, Spain, France) where brother-sister relations are legal. So, let 'em have fun if they want for what it’s worth. It won’t change anything.
Unless they are also geneticists with access to a lot of diverse genetic material (i.e. frozen sperm and eggs) we are doomed. So, I picked something else…they need to get busy impregnating the last woman with eggs and sperm from as many of that stock pile as they can, and then raise the children and start a breeding program asap…and hope nothing happens in the mean time.
Is that categorically true? Or could we imagine a brother and sister with exceptionally clean alleles whose children and interbred grandchildren would be reasonably healthy, and who undertake to teach their offspring the necessity of mixing it up – breed with your cousin instead of your brothers; with your second cousins instead of your first cousin, etc. Can you explain why it’s an automatic death spiral?
The 50/500 rule (which I assume is what Prof. Pepperwinkle and XT are referencing with their doomsaying) is not an absolute inviolable law of nature, it is a rule of thumb. It is in particular a rule of thumb used by conservation biologists, who typically deal with species under a lot of stress (usually by humans, in one way or another). These surviving siblings and their offspring would have little competition for resources and few natural predators, and would be in a much better shape than most species. Their odds may be bad, but that’s no reason to not have a go at it.
Well, I’m no geneticist nor do I play one on the SD, but from here:
This is why if either the brother or sister were doctors specializing in reproduction AND had access to a bank of frozen sperm/eggs from a diverse population we might have a chance if everything went right:
From memory we hit a population bottle neck about 70k years ago where we almost went extinct. I seem to recall that at one point the human population was down to a few thousand at most. Today, with modern genetics and stocks of frozen sperm and eggs as well as the know how to use it we might have a chance with just two people (what if the woman has complications in child berth? What if one of them catches the flu or something else that proves fatal?) IF they were lucky AND they had access and know how to use the technology. If they didn’t I’d say the odds of two people by themselves breeding enough to ensure a viable human population is just about zero. Even with it I’d say it’s pretty long odds for just two people.
And New Jersey and Rhode Island. IIRC those are the only two states in which there is no incest statute. As long as both parties are consenting adults of course. Can’t get married but its not illegal to have sex. In NJ at least it does bump up the age of consent from 16 to 18 if it is a blood relation.
Ok, so there seem to be a couple of different hazards. I understand the chances of extinction are high based on environmental concerns: if a hurricane hits your idyllic tropical paradise and kills the brother and sister, then the race is dead regardless of any genetic concerns.
But I didn’t quite follow why the genetic concerns on their own are so certain to be fatal.
So let’s assume we’re talking about physical safety for a thousand years – no natural disasters, attacks by predators, or loss of food supply.
Is the race doomed solely because there’s just two people? And do we even care that they’re brother and sister at that point?
If neither one has a resistance to some disease that crops up then their kids won’t either. Adios muchachos, to paraphrase from Aliens. Genetic diversity is what allows some humans to survive when something catastrophic like a new variant on a disease crops up. The reason it’s important in this situation is that a brother and sister are going to be less genetically diverse, and the genetic material they pass on to their offspring will also be less diverse. To be viable for the thousand years you are proposing they are going to face things like disease, and all it’s going to take is one disease that this brother and sister don’t have any immunity to at all and are particularly susceptible to. Every year someone dies from, say, the flu, while others get it and survive…and some folks, even without immunization never get it even when exposed. If a flu strain came up that this brother and sister were particularly susceptible too then so would their descendents be…and it could easily wipe out the entire population, especially since it would be pretty small and concentrated for many, many years…hell, for centuries.
Yeah, but the OP isn’t ‘can they survive’ it’s ‘should they bang’? VERY different questions.
In the end, it boils down to ‘is the incest taboo strong enough that humanity should lay down and die instead of violating it?’
My answer is get banging. Anything’s better than lying down to die without trying. Hell, even with the genetic angle, extinction isn’t a lock.
Assumptions:
Start with 1 male and 1 female, siblings
Assume each female has 12 children
Assume a 50% mortality rate from whatever (including genetic defects)
Assume children born are 50-50 male and female
First generation 2
Second gen: 6
Third generation: 18
Fourth generation: 54
Fifth generation: 162
Sixth generation: 486
Seventh generation: 1458
Eighth generation: 4374
Ninth generation: 13122
Tenth generation: 39366
At which point warfare breaks out over who are the TRUE descendent of nuclear Adam and Eve.
Why would laws or the creep factor of incest even play a part? I never, ever want to have children, and I guarantee you if it was the end of the world I’d be trying to get pregnant ASAP. Duties change at that point.
If my sister and I were the last two on earth, I’d probably convince her to try it. But no way would we actually have sex. We’d use a turkey baster or something.
Guinea pigs (or hamsters) in captivity all come from a population of like 2 pigs.
Incest birth-defects are over-stated because of the yuck factor.
Humanity’s got a fighting chance if the woman is healthy and can produce a couple/few females (and ideally a male, otherwise Dad’s going to have to have sex with his daughters).
Of course, this is easy for me to say. I don’t have a sister.
That’s why, Anaamika. The incest taboo is pretty far down in the subconscious for some people. Not everyone, certainly. But I bet a majority of people would wrestle with it for a while before making the approach.