As I’ve said in other threads - look at the sicko Fritzl in Austria. He locked up his daughter for 20 years, and she had 7 children from him. One died at birth, one started having seizures at age 19(reason unknown, but more likely environment), and the rest, especially the two raised upstairs in a normal environment, turned out OK.
The problem is that a lot of genetic problems are recessive. They only manifest if the child receives a defective copy from both parents. If a “breeding pair” are closely related, the odds that they will both contribute a defective gene - the same one - is much higher. Plus, there’s the risk of random mutations - if a random mutation wrecks the one good gene in a person’s DNA, the matching defective one will manifest; whereas typically, a person inherits two good genes so if one mutates and so fails, the other is good.
So the risk of doubling defective genes and so of certain genetic defects is much higher if the initial starting population, the gene pool, is small. Variety is the spice of life. However, if the starting population is relatively healthy, odds are it will not be a serious problem.
Another key issue is how many kids per generation. Firstly, because of how fast population grows, but also to ensure every chromosome survives. A parent is guaranteed to give half their chromosomes to the first child. With two children, odds are they have between them, 3/4 of each parent’s chromosomes. The third, we’re at 7/8; the fourth, 15/16ths. by 10 kids, there’s a safe bet every chromosome is in play. There’s no point in bringing 46 chromosomes to the brave new world and never putting many of them in play, when survival depends on genetic diversity. Those first few generations are going to have to spread the love…
Another point about comparing the animals who have been reduced to seriously low numbers and recovered to some degree is that all of the ones mentioned have multiple births whereas humans having two or more babies at once are the exception rather than the rule. 1 in 30 for twins and 1 in 1000 for triplets
Victoria’s haemophilia is something of a case study of the problems with in-breeding … so the point is not every child will be fucked up …
Someone did a study on field mice in central Ukraine … they found about a 3% birth defect rate … they did the same study on the field mice nesting on the old sarcophagus at Chernobyl and found a 6% birth defect rate … certainly intolerable for humans … but the mice are thriving …
I think the idea is to use the 1:25 when assigning spots in the Doomsday bunker; there’s no reason not to default to the natural ratio in the next generation.
The cause is a mutation … the mutation is spread by breeding in the general sense … in-breeding allows the mutation to be more fully expressed in the off-spring … like Mendel showed with his pea plants …
If the mother passes this recessive gene to both her son and daughter, then the offspring of the son and daughter will have a much higher chance of developing hemophilia than if the son and daughter had out-bred into the general population … that’s a problem …
Positive traits can also be had with in-breeding … if this son and daughter had excellent facial features … at least a few of their offspring will also have these features … having these few may well be worth having to deal with all the other offspring …
The post I was responding to was a pretty cryptic one-liner. We’d both hope she was thinking as you said.
But it didn’t smell that way to me. By that point in the thread everyone was still talking abut natural disasters with the implication of population collapse happening too fast to create and stock a bunker. That idea first appeared later in the thread.
Not with that particular bad gene. This can only happen if both male and females can be carriers of the bad gene. But in males, a single instance of that hemophila gene is always expressed, and before modern medicine, males that inherited it virtually always died before they had a chance to reproduce. So there were no male carriers of that gene. Certainly none of Victoria’s male descendents who had it managed to reproduce.
If it were a gene on an autosome, then you would be right. And there are types of hemophilia that are on autosomes. But the Victorian gene was sex-linked on the X-chromosome and it works differently. They teach this stuff in high school biology. Didn’t anyone pay attention?
Prince Leopold, Victoria’s eighth child, passed it on to his daughter, Princess Alice, who in turn passed it to her son, Rupert Cambridge. Once you get your facts straight, maybe you could edify us on why in-breeding had nothing to do with the spread of hemophilia all around the royal houses of Europe.
I assume because it was a X-linked disease. Therefore, AFAIK, none of the women had the actual disease - which they could have, with inbreeding. However, since the men have an XY pair, they have a 50-50 chance of inheriting the mutant diseased X from a carrier mother. If they get the mutation X, they WILL develop hemophilia. If not, they and their offspring are not at risk.
Inbreeding has nothing to do with it. Simply, Victoria (or her parents or grandparents?) developed the mutation, and passed it along. Because of the prominence of the family, it is easier to trace the disease and it affected some very prominent people.
Plus, that would be about the time Mendel’s work and others became popularly known, so it was useful in explaining the disease and its trajectory more concisely.
Have any of Victoria’s offspring reproduced with one another in subsequent generations?
Found this. The Victoria family tree. http://tapnewswire.com/2011/12/did-hemophilia-gene-reach-queen/
Since Edward VII and Prince Philip did not carry the gene, presumably the main royal family branch is in the clear for now.
Wat’s not indicated in the diagram is the women who MAY be carriers. The author of the diagram is assuming a lack of males with the disease indicates the mother is not a carrier… which may be true or dumb luck.
Princess Alice, for example, has only one indicated grandson through her daughter, who is ok. That may be because her daughter is not a carrier, or because of luck.
But the diagram does indicate that the gene is slowly “weeded out”.
Too late to edit.
Sorry, the page itself is a flaming nutbar, but the diagram still stands.
(It’s actually quite funny in a sad way - claiming that Stalin, Hitler, Churchill, and Prince Albert and possibly Victoria are illegitimate offspring of the Rothschilds. WTF??)
if we are allowed to assume that scavenged medical supplies are available then there’s various fertility meds which can increase those odds. Apparently gonadotropin can increase the odds of having twins or more to almost 30 %. Seems like that would help quite a bit.
Because it’s sex-linked on the X chromosome, inbreeding makes it more likely that it will be expressed in women. But not more likely in men. That is, not more likely than just plain old breeding. For male descendants.
If the families are too big, you will be sending toddlers and very pregnant women out to help clear new fields, plant crops, ten goats, etc. unless your Brave New World includes tractors and other equipment that never need maintenance (or fuel). If they are hunter-gatherers, I suspect a group of 20 to 30 is the limit a fairly broad area will hold. Too big a group and you can’t hunt enough in that one area to feed the whole… Unless you follow buffalo herds that are bigger than the eye can see.
But I’m going to go out on a limb and suggest that 2 people is all you need to repopulate the world, if you are lucky and they are not harbouring any significant recessive bad genes. All the above discussion points out - the problem is more “monoculture”, a lack of diversity. What affects one, such as susceptibility to a disease, affects all. it’s not that a group “loses vitality” and gets stupid over the generations.
For most of human history, that’s pretty much how it worked. Not toddlers, quite, but kids would start doing whatever jobs they could by about 4 or 5 years old. In fact, people had big families precisely so they could get more help around the farm.