It seems to only apply if the gene is expressing, so removing one for the sake of saving future generations the trouble doesn’t seem to be on the board, and how is it defining ‘serious’? Just potentially fatal, or do disabilities that would negatively the child’s ability to interact with society, even with accommodations like VISORs or mobility devices, also count?
But…that does suggest standard medical training and equipment does include gene therapy, so it would be easier to start doing it even in lesser situations, even if they’re technically disallowed.
I seem to recall a TNG episode where they dealt with the problem of clones and the non-viability of a population of… I think maybe 5 people initially? If there was such a technology, you’d think they’d have mentioned it prior to proposing combining the clone colony with a less developed colony recently rescued by Enterprise.
But I understand that that’s not a definitive argument. The canon often reshapes itself. Sometimes subtly and keeping pace with developments in our own society (both social and scientific), other times not so subtly.
IANA geneticist but I’ve studied it a little. but I’ve always thought this an interesting notion.
Suppose for instance that you have a group of individuals A, B, C, D, E, F…
A and B produce children AB… C and D produce CD, and so on. If you’re in first generation your choices of a mate were B, C, D, E, etc. Now you have about half that because AB implies inbreeding. There’s still CD, EF, GH, IJ, etc.
So an AB mates with a CD. Kids are ABCD. Choices are halved again. Mates will have to be EFGH, IJKL, MNOP etc. So the ABCD’s choice is an EFGH. Those kids are ABCDEFGH; they pick IJKLMNOP, QRSTUVWX, and so on.
Say, what if an ABCDEFTH met someone who was somehow IJKLDNOP, would that be ok? The D means there was a common ancestor so there will be some inbreeding. That’s more realistic too than imagining all of the kids from family A would marry the kids from family B.
My assumption for many years is that we’re all inbred to some degree. As my alphabet above hopefully shows, you’re going to run out of options pretty quickly. But inbreeding doesn’t mean we’re automatically born as total freaks.
In very small populations or repeated across generations, e.g. royals…
Yeah, that “replicative fading” was a deeply stupid plot point. If you have advanced enough biotech to produce generation after generation of clones, then you are going have advanced enough biotech that you can repair any errors in the DNA. And to decode and store digital “reference copies” of everyone’s original genomes. And to shuffle around the available genes to make an unlimited number of unique individuals. And remove any bad alleles. (As implied in this thread, inbreeding is only a problem when the population has defective alleles circulating in it.) We’re talking technology barely beyond today. (Except for making a digital reference copy of genomes–that’s a technology from 20 years ago.)
But at least “replicative fading” isn’t as stupid as “Rybo-viroxic-nucleic sequences.”
The bolded bit is where this all falls apart, in my mind.
Were I in charge of such a situation, I’d make a rule that breeding in at least the first few generations must be as diverse as possible, since we can’t rely on later generations retaining the knowledge of genetics needed to avoid such problems.
So, yeah, you can marry whoever you want, but your kids will be produced via some sort of artificial breeding, so that each woman has kids with as many different men as possible, and each man impregnates as many women as possible. No kid in the first generation should have any more than half-siblings. Maximize the genetic diversity as much as possible, as long as possible.
OP asked, “In real life, is 200 years enough time” and I was going on post 2’s assumption of 4 kids per couple, which seemed a reasonable goal. 23x23 on the other hand would yield 529 kids, possibly requiring women to carry/deliver 23 babies each, and each person would be required to raise 11.5 of them, etc. while accomplishing whatever other tasks are needed for survival. I’m not familiar with the episode; do they have tech on board that they brought with them to overcome the problems?
True, A can mate with B, C, D, and E; B can mate with F, G, H, I…but in a couple generations you’ll end up with the same question of parentage I think. You end up with someone in gen 2 who is ACHT wanting to mate with someone who is BEHS and saying “Wait, you both have the H, common ancestor.”
In generation 3 you have eight letter signatures and no letters can match. We only started wth 23 pairs of people for mating. At generation 4, two people with sixteen letter signatures can’t avoid overlapping.
Gender can become a spoiler, too. There’s an ACHT and there’s a BEFS, so they’re good to mate. Except they’re same sex, can’t reproduce with each other.
And if we’re looking at doing this over 100 years, we have to acknowledge that the forefathers die before we reach the end, taking them out of the count. But that’s small potatoes.
You hear people say “I’m a distant cousin of George Washington.” I imagine geneticists factor far back the mutual ancestory lived to determine what impact there might be. Heck, in some places cousins (2 common grandparents) are free to marry.
I found this, which seems to have asked a similar question in the natural world.
Fifty effective individuals – the IUCN standard for avoiding inbreeding – equals a total population of 250 to 500. This means that, in a hypothetical apocalypse, humanity would need a lot more than a handful of survivors to repopulate effectively.
However, to retain evolutionary potential – to remain genetically flexible and diverse – the IUCN criteria suggest we would need at least 500 effective individuals. That requires a population of 2,500 to 5,000.
Yeah, there’s no way to make this system perfect. I’m just trying to stave off the most obvious problems for as long as possible. At some point, you’ll have to accept some risk, it’s just about minimizing that risk as much as possible for as long as possible.
My mom is the whoever manyth generation Amish in her line in this country [they came over in the 1670s] and is therefor inbred - she married English, so her kids would be safe as they wouldn’t be marrying cousins [she was banished because she didn’t go back after rumspringa, I vaguely know the names of her brothers, but have never met anybody, when we went through the town on the way westwards for vacation, he and the woman I assume was his wife turned and walked away when they saw her in town.]
Amish have a propensity for certain health issues exactly because of the inbreeding. Sucks, but it is what it is. I always thought they should hook up with some of the more old fashioned Mennonites for new blood.
According to a genetics prof I interviewed for a term paper, in Jewish populations Tay-Sachs is the bad boy. In Caucasians, it’s Cystic Fibrosis. Each group has an Achilles Heel.
But I wonder if these smaller populations are bulletproof to other diseases. In some African populations, it’s sickle trait.
High price to pay if you get the gene from both parents, but…
Eh, lack of genetic viability wasn’t the real problem in “Up the Long Ladder”, anyway. The real problem in that episode was that the Enterprise crew wanted to arrange orgies of hot clones and space-Irish. There’s no indication that they got to participate, but maybe just organizing it was all they wanted?
This is discussed and similarly treated in the pretty good post-apocalyptic novel The Last Ship by William Brinkley (very different from the TV series of the same name), in which a U.S. Navy destroyer with both male and female crewmembers survives a full-on global nuclear war.