What is the viability of one healthy, young (say mid-20’s) woman being able to start the re-population of earth so long as she has multiple sperm donors?
What would the genetic issues be within a couple of generations if she had access to multiple racial partners?
And no, the daddies will not breed with daughters/granddaughters, just from there it will be half-siblings breeding together and matching up from there.
She can only be pregnant one session at a time no matter how many sperm donors you have. What’s needed would be many women and one man.
Sorry Runner, that doesn’t work for what I am working on. It’ll be 1 woman with multiple sperm donors. So trying to figure out the repercussions.
I had found a website that mentioned genetic defects with a percentage rate of 12.5% for half siblings creating babies together, but it didn’t go further than that first generation. I am looking at a woman who might have say 10 children. Let’s even say they are half male and half female and she matches them based on not being from the same daddy or race. Like she matches her half-African American daughter with her half-Hispanic son to produce the next generation & so on.
Is this a “need answer fast” post??? AS A MAN SHOULD I BE WORRIED???
The viability is good, btw. Even brothers and sisters mating together don’t usually have children with horrible birth defects.
Wouldn’t it be better for the children to mate with the first generation daddies (but not their own fathers)?
Then also for the third gen to again mate with the first gen men? By the time you got to fourth gen, the co-mingled blood should be quite low right (only sharing a common grannma)
Does that mean you detect and terminate first-generation male offspring?
It never occured to me -
But how do you get from my post to that?
Couldn’t it just be like this…
EVE -
child with Adam- boy1
child with Peter - Girl 1
child with Paul - girl 2
child with Simon - boy 2
child with Frank - girl 3
child with Saul - boy 3
child with Bob - girl 4
THEN
Girl one child with Adam- girl5
Girl Two child with Simon - girl 6
THEN
girl 5 has child with boy 2
girl 6 has child with boy 3
And it’s even worse than just having one pregnancy every year or so. A woman needs to have at least a couple of years of not being pregnant if she’s going to have another healthy pregnancy and baby. So a woman can only have one or two babies (twins, not gonna go into multiples) every three or four years. If we assume that the woman is 25, and that she undergoes menopause at 55 (a bit late), then that means that she has 30 childbearing years…but she won’t get but a dozen or so babies, IF she gets pregnant every time she wants to do so, and IF she has some twins, and IF she’s willing to get pregnant every 3 or so years.
As for the rest of the question, I dunno. It’s certainly not a scenario that I’d want to be in. And I’d wonder why the sperm donors wouldn’t breed with with the female children who weren’t related to them. I mean, yeah, if the guys just think that having sex with teen girls who are at least 35 years younger than them is icky, I can understand that. But it would be the best way to solve the interbreeding problem.
This is the optimal solution. As long as they’re willing for female children to reproduce with the older males as soon as the girls hit reproductive age, of course. They’d get a much better genetic spread more quickly, no inbreeding for enough generations that it would become a non-issue.
Also, I think rational actors would be more willing to set aside the squickiness of the age gap than they would be with 13-year-old guys mating with their 11-year-old half-sisters. I am mentioning this because it sounds like the OP is writing a sci-fi story, and the squickiness would be a central plot-point.
Anyway, I made some mspaint diagrams to help illustrate the potential outcome:
Generation 2
Generation 3
Generation 4
Obviously it’s idealized; it assumes at least one fertile female in each generation. There wouldn’t need to be any inbreeding until it comes time for the 4th generation to produce the 5th generation, at which point all the contemporaries in the younger generation should be sufficiently far-removed to reproduce with each other (sans siblings, of course).
This has got to be the nerdiest, most pointless use of mspaint. Ever. But I was bored and it was a good intellectual exercise. 
Cite for the fact women need downtime between pregnancies or problems will arise?
I ask because while it may not be the style anymore talk to some older folks from rural areas and its not rare to find those with double digit siblings, some approaching twenty siblings. Hell here in Trinidad it isn’t rare at all to hear older people from rural areas have 17 brothers and sisters, it might be unimaginable to me and my wife but there apparently were some women who spent their entire fertile life pregnant basically.
Hell for a modern example look at the Quiverfull religious movement, and what about the Dugger family on TV? I believe the wife had around twenty pregnancies in twenty years and only with her most recent pregnancy did a problem arise.(and even then mother and child survived due to medical care)
That seems… exaggerated, given the amounts of Irish twins around. “Having pregnancies too close together increases risks”, ok; but the way you put it sounds as if it’s impossible for a woman to have healthy Irish twins without herself having a lot of medical problems - much less 10 kids in 14 years, and I know two cases of this; they’re exceptional but not impossible.
“Having too many children increases risk” among other things because eventually the woman gets to “elder gravida” country.
Is this related to the recent episode of Archer?
eta: as a dude, I prefer the version where there’s 1 man (me) and a bunch of women who need to repopulate the Earth, but either way, I’m willing to do my part.
Rachel, yes I’m working on a plot. 
The bottom line is basically 1 woman is left on a planet she and her cohorts were exploring, the reason the daddies don’t breed is they died before the oldest girl is old enough to breed.
That’s why I’m trying to figure out mutations and what she’d have to deal with and teach her children to deal with before she dies.
That’s why I was looking at a chart with figures on inbreeding. I like the 12.5% chance of the half-siblings having a child with genetic issues. My math skills are simply not strong enough to take it from there and figure it out.
It wouldn’t work. The population size is too small, and the genetic inbreeding would result in a damaged population. IIRC, most studies of primates suggest that a population of 250 mixed sex individuals is the minimum necessary. Diversity is best for species.
That said, if you wanted to try, the best way to do it would be to destroy any male offspring as soon as possible until the female population equaled the male population. If you can’t give abortions, then killing the babies at birth will help the mother recover quicker, as nursing acts as a natural form of birth control. Siblings mating with siblings simply won’t work for humans, especially since the inbreeding would only increase with each subsequent generation. Look at royalty in humans for a very minor example of the damaged offspring that will be produced.
Race isn’t a good measure of genetic variety, especially since humans are an incredibly homogeneous species, and race is mostly culturally constructed, not biologically. Therefore, you can have a Caucasian and a Hispanic individual who have extremely similar ancestry, more than that same Caucasian compared with another Caucasian. Since Africans statistically have the most genetic best, if you have no access to genetic testing, then mating with individuals from Africa will likely to produce the most robust population, but that’s only a matter of guesswork.
What? Why would you kill the baby boys? The female and male populations will be equal as soon as the older generation dies. Then you’d be left with an all-female world. Sexes re-balance at the first generation- no need to kill anybody.
And cite for the 250 minimum?
Where are you getting this number from? 1/8 is way too high.
The Grapist Lives!
I’d be wary of overthinking it. First of all, how much does your babymama know? Is she a geneticist? For most of us, what we’d tell our kids would be something like, “Don’t make babies with Eve or Mary - you share the same daddy. Your other sisters are okay, though.”
I mean, they may not be *okay *okay, but they’re going to be the best chance you’ve got, assuming you don’t have some phlebotnum to turn off the human sex drive. They’re going to have sex with someone, so you tell 'em what you can to better their odds.
Beyond that, it’s a story, not a journal article. Use what works for your theme. Do you want to write a story about the arbitrariness of “race” as a construct? Then write it so that SonsofAdam refuse to associate with DaughtersofSteve because they misunderstood their mother’s instructions. Want to write about the power of Love? Maybe each father’s offspring form a separate clan, and intricate marriage rituals ensure that you only mate outside your clan, but then one day a SonofAdam falls in love with a DaughterofAdam and drama ensues. Want to write about the evils of incest? Then write about a monster baby - even if the odds are low, they’re never zero, so you can have a monster baby if you like.
It’s your story. You’re a god here. You make the rules, and you break them as it supports your theme.
ETA: Oh, and if food is plentiful and the mother young and healthy (again, that’s up to you what you decide to write), then it’s entirely possible to be more or less continuously pregnant, even with breastfeeding. Breastfeeding only works as contraception when women are very thin and the breastfeeding is exclusive and on demand, even through the night. Most American women are far too well fed to rely on breastfeeding for contraception.
FIrst - no, 12.5% is the duplication of genes. Whether any of those genes are defective, and in such a way that they cause problems (i.e. dominant, or have effcts on reproduction) who knows? There are plently of instances of sibling incest or father-daughter incest (Austria?) where the children do not exhibit serious problems, except maybe developmental/environmental issues. A related issue might be the variation of the parents; in “the good old days” inbreeding in a village was probably a bad idea because the gene pool might be very small to start with.
As of the “next generations”, in a scenario like this - what is the fridge life of frozen sperm? WOuld it be worthwhile to sore a wide variety of genes unto the Nth generation? Would the womb donor be exclusive with each male until pregnancy was confirmed so that the parentage could be definitively established?
OTOH, it’s a giant crapshoot. a decent number of women have trouble reproducing; the number of infertile couples is not insignificant, and many women have several miscarriages for one or more healthy births. Some can pop them out one after another. Pinning your hopes on one woman - good luck!
Mathematically, yes, it would be better for a preponderance of females; but remember that every female is a double-X chromosome, one of which comes from the father. So, by the second generation (grandchildren) there will be a large number of the population who have almost no genes in common.
What is a viable population? Nobody knows. There are theories, all hand-waving. The closest you might come to real-life examples would be the populating of the isolated islands of the Pacific. The polynesian expansion was probabably limited in some cases to a canoe-load or two, particularly the furthest islands, where the population grew from there. (I wonder exactly how many canoes made it to Easter Island?) Also a bad example in some respects because many of the islands traded and had assorted genetic interchange.
Not just “Irish Twins”, the French-Canadian population was notorious in the days before TV for popping one out every year in good Catholic fashion. While 20 in a row might be a stretch (sorry) for most women, 10 children was pretty common; IIRC for example Celine Dione has 7 siblings. (OTOH, she and hubby jumped through medical hoops to have any children). Even those 4 or 5 child families I knew growing up, the kids were not that far apart. A lot of my classmates, their sblings were only 1 or 2 years ahead or behind in school. The only difference, is nowadays parents usually stop at two.
Heck, you don’t even need to look to rural areas. I grew up in the city, and my first crush was one of nine or ten kids (I forget), with no multiple births. The first four were all one year apart. The other ones may have had a gap of one or two years at the very most.
I’m sure there’s an increased risk for not waiting between kids, but it happens in real life, and, for the purposes of a plot in a story, I don’t think we need to assume 3 years between kids.
My older brother and I are 10 months and 26 days apart. I was perfectly healthy. While it may increase the likelihood of having an unhealthy one if they’re too close, it’s certainly possible, and even common, to have healthy ones close together.