Last woman on earth...

Miscellaneous and Personal Stuff I Must Share
1

My friend and I were having an argument about whether the human race could be repopulated if there were only one woman left on earth, and lots of men. Should we just give up at that point or hang on and keep trying? I mean, from a genetic standpoint, is it possible?

Thanks!

krekk

2

I’m no geneticist, or even a biologist, but as long as she’s not a carrier of anything lethal, e.g. hemophilia, I don’t see why not.

3

Genetically it’s more viable than one man and lots of women (sadly…) as the men can chip in with X chromosomes as well as Y, whereas in the other case you have all the Y chromosomes you’ll ever have. Also men stay fertile long enough to breed with her daughters, even granddaughters, so at least you get to use your entire genetic base. Whether that’s enough… shrug.

Better hope she wants lots of babies, though, and that your advanced obstetrics have survived whatever catastrophe led to this pass.

4

Well, your next generation is going to be limited to the number of children one woman can/is willing to have, only half of those will be girls, and they will all be half-siblings. There will presumably be unrelated men from the first generation still alive and ahem active when the girls from the second generation come of reproductive age, so you can increase the genetic diversity somewhat. Theoretically, there will still be unrelated men from the first generation capable of breeding when girls from the third generation become fertile. If you start with a woman who was very young, very fertile, and willing to be monogamous until pregnant and then switch to a new guy for the next baby, and all her daughters were willing to do the same…you could theoretically build up a genetically stable population. Of course, when the last men from the first generation die, the entire world’s population will have the same mitochondrial DNA, and I just don’t know how big an issue that is.

In practical terms, though, I don’t think it would work. That sort of reduced population is going to make it awfully hard to keep up with the sort of medical and hygienic technology we take for granted that contributes mightily to our life expectancy and low infant mortality. So the odds of your initial woman or the babies dying early go way up. Also, I think the men would get to fighting over the woman/women and wind up killing each other off. And, of course, that sort of unstable environment is not conducive to successfully raising babies.

5

Power is unaffected by the disaster (say it was a biological weapon that somehow targeted women and the one woman was immune, and the weapon will have decayed by the time children are born) they could always use frozen sperm in future generations, and possibly frozen eggs as well (although not eggs until they have several girls matured to make sure they don’t take risks with more than a percentage of their women)

6

You can’t say that half of her children are going to be girls, it doesn’t work that way. For a large number of births over a population, the number of boys and girls tends about 50/50.

But for individual mothers it doesn’t. You probably know families with 3 boys and one girl (like mine) or 4 girls and one boy, or even couples with all boys or all girls.

There are biological factors involved with particular individuals and your ‘last mom on Earth’ might not give birth to any girls at all.

7

This gives a new dimension to the term “getting busy.”

8

Assuming technology still exists, she could be an egg donor and potentially have hundreds of children. If all her female progeny did the same she could have hundreds of thousands of descendents within two generations.

9

I’ll assume for a moment that all the egg and zygote freezers are malfunctioning, and we have only her DNA and the mens’ to work with. I think you’d be better off giving her a few rounds of fertility drugs, harvesting and fertilizing the eggs and implanting them into the abdomens of some of the men for gestation. At least get a few dozen eggs harvested before she gets pregnant herself. It’s theoretically possible, just as women have carried abdonimal pregnancies to term. It might kill them to deliver if the bleeding can’t be stopped when the placenta separates, but if we leave the placenta attached to atrophy on its own, that reduces the risk. Still, for the chance to have a few more girls born instead of all these redundant men, it’d be worth it.

If there are still frozen zygotes available in IVF clinic freezers, then it’s a no brainer. Surgically impregnate some men and see what happens. Impregnante her with someone else’s eggs after she’s had her own genetic offspring. This will keep the gene pool more diverse than she can do on her own.

10

Availability of uteri is still a bottleneck though, barring a big leap in technology - which is unlikely with such a small population all working their arses off just to stay alive.

Edit: The almighty uterus aside though, men are hardly “redundant” when you have a small population to provide for, even if they’re not getting to procreate. :rolleyes:

11

Fertilizing the egg isn’t beyond our technology. Cutting open a man’s abdomen isn’t. Inserting an egg isn’t. I don’t know the best place to put it, and yes, we’ll probably lose a few men in our attempts (still, someone knows more than me - at least to know where the dozen or so recorded cases of abdominal pregnancy implanted. It’s a start.). We know enough about hormones to make a male body very very similar to a female body.

Maybe it wasn’t clear from my first post: women *have *carried healthy babies to term who weren’t in their uterus. They were in their abdominal cavities outside the uterus. There’s no reason we know of why the same couldn’t be done in a man’s body.

Even if you only get a dozen healthy baby girls in 10 years with this research, you’re way ahead of the game, compared to the 2 or 3 healthy girls likely from one woman.

Remember, gestation only takes 9 months, but repeated close gestation tends to lead to problems with both the mother’s health and the infants’. You really can’t keep her breeding nonstop and expect good breeding stock to result.

The men in the OP’s hypothetical seem to be without number. There’s no indication of a “small number”. Only one of them can impregnate our female at one time, and that only once a year. Therefore, for conventional reproduction, the rest are redundant. I didn’t say they were without value. I wasn’t discussing how I would build houses or prevent starvation, I was discussing how I’d handle genetics and breeding.

12

Nope. Ain’t gonna happen. Waaaaaay too much can go wrong in any pregnancy or for any woman to put the existence of the human race on one woman’s shoulders.

Let’s say you have the ideal:

  • one healthy 14 year old girl who has just completed menarche and can be expected to hit menopause at age 50, giving you 36 years of child bearing.
  • 36 males, at year one, ranging in age from 18 to infancy, so that as each comes up on their year of fatherhood, they are at their peak fertility.
  • a large supply of other males who are willing to wait for second or third generation girls to become fertile before they have their chance to sire offspring.
  • a willingness of the entire group to put aside monogamous bonding, divorce procreation from love, raise babies they did not sire as if they had, go without heterosexual sex for their entire lives except the few months they have to conceive a child with either the first generation woman or her daughters and and granddaughters, AND perform on cue like a stud bull with a woman they may not find attractive or likable.
  • someone to keep track of all conceptions to maximize genetic diversity and prevent too many degrees of incest.

Now, let’s add reality:

  • one third of all conceptions end in spontaneous abortion because of chromosomal mismatches or other problems.
  • another significant percentage of all pregnancies end with stillborn babies or babies which die during or shortly after birth.
  • another significant percentage of all pregnancies involve babies with physical deformities or other birth defects which compromise their ability to live, conceive, and carry to term the next generation.
  • one thing goes wrong during the pregnancy - hyperemesis, eclampsia, placentia previa, placentia abrupta, uterine rupture, ectopic pregnancy, baby’s head to big for mother’s hips - and the mother dies.
  • not even the Duggars have managed to produce one new baby a year. They’ve had 19 in nearly 22 years, and two pregnancies resulted in twins. The last baby spent significant time in the NICU, which means in this hypothesis, the baby would have died. The mother also needed significant medical care, which would not have happened in the hypothetical situation.
  • in pre-Industrial societies, expect half the babies to die before age five.

Now add in the human element:

  • without a mandate all the individuals except with the kind of fervor needed for religious conversion and people willing to police the most private behavior of others, it’s an exercise in herding cats.
  • you’ll have to lock up the first generation woman and deprive her of all individual rights to make sure she is safe, healthy, and has sex only with the sire chosen for that year’s baby.
  • you’ll have to lock up the men to make sure they don’t have sex with the woman before it’s their turn.
  • you’ll have to ensure that each man takes his turn, and that those in power do not abuse their power by having lots of unapproved sex with the one woman in existence.
  • once babies start arriving, you’ll have to lock them up to keep them safe and health and the girls viriginal until it’s time to start making babies.

This doesn’t even take into account the founder effect, where any particular genetic trait from the mother, good, bad, or otherwise, is passed on to a majority of her children. If it’s good or neutral, no problem. If it’s bad, the population takes a nose dive in the second and third generations. Nor does it take into account all the bad things nature throws at a small population of humans. One outbreak of influenza, one bad choice in food or water, one rabid predator, one fire, et cetera, et cetera, and your population is toast.

I recently saw a documentary on the human colonization of Australia, some 50,000 years ago. The statisticians and scientists they talked to came to the conclusion that it was virtually impossible for one woman and a group of men to populate the continent. At best, a founding group with those numbers lasted five generations before disappearing. For a sure bet, you needed at least 80 heterosexual couples and a fair sprinkling of single women of child bearing years.

13

I would like to point out that the success rate of freezing early embryos is far higher than freezing human eggs.

The number of uteruses available for gestation is still a major limiting factor, but in between the remaining woman’s pregnancies you could use drugs to get her ovaries to cough up abundant eggs for a few cycles, then fertilize and freeze them.

One advantage here is that you can pick out which embryos are female and preferentially use them, thereby skewing the sex ratio of children born quite a bit. Any mature daughters who happen to be infertile themselves might become host mothers for those embryos.

And there’s that whole experiment with male pregnancy thing. True, outside the uterus pregnancies are usually serious, even catastrophic, but the naturally occuring ones implant at random. If we’re doing this deliberately we have some control over placement, which might considerably reduce the risk.

14

Well, yes, I know that. But odds favor there being a roughly 50/50 split, even for an individual woman. The further you get from that division, the less likely it is to happen.

15

The OP asks if the human race* could *be repopulated, so the answer would be yes. But as other’s pointed out, it’s not a sure fire thing, and impossible if she’s infertile. Let’s try to avoid this situation.

16

How low did the cheetah population get? I’ve read that they’re “essentially clones” in popular rags, because the breeding population got so low that they have almost no (or no) genetic diversity left. So they managed it with something more than one female, I believe, but they’re absolutely sunk if some pathogen pops up that they’re all susceptible to, or if their environment changes and there aren’t enough mutations to come up with a fit in a timely fashion.

17

For whom?

18

For an increased chance of survival of the species with enough genetic diversity to withstand future stressors.

Assuming that’s what we’re going for, here. Personally, I’m all for letting the cockroaches have their turn.

19

That’s where I am, too. I mean fine, if someone wants to sacrifice themselves blah blah blah, but that kind of sacrifice wouldn’t be “worth it” to me. Death and extinction suck, but there are worse things.

20

It’s happened with a few bird species, the Laysan duck and the Chatham Island Robin for example, but I don’t think any humans would really be able to manage it, short of the one remaining woman being of an amazing health and fertility.

The closest I can find to the OP for a mammal species -having normally a single baby each year- is the recovery of Northern Elephant Seals from an estimated 20-100 individuals to current levels of around 127,000, but surely quite a few more than one of the 20-100 were female!