One of the entire reasons for the Howard Project was to interbreed long-lived people. The long-term effects were (a) long-lived people and (b) birth defects. Also, lots of redheads. Scientifically, he had cause to be concerned about birth defects.
Also, at that point, he’s still within a couple normal lifetimes of having been raised in Missouri in the 20’s. I always read the consanguinity issues as avoiding the real issue, which is that he didn’t want to do it with one of his kids. By the time he’s having sex with his mom, his clone-sisters, his transgender partner of a couple centuries and a couple of human-bodied Pinocchio computer sex-kittens, I think he’s past that little quibble.
Since there is crossover, you will share, almost certainly, very close to 50% of each of your parent’s and 25% of each grandparent’s genes. But taking TimeWinder’s scenario, assuming you were your own grandpa, you would end up with 1/4 + 1/16 + 1/64 + … = 1/3 of your grandmother’s genes and 1/7 of your grandmother’s genes if you did it with her instead.
Is there any point where it’s a near-100% certainty that your ancestors/descendants will not have any of your genetic material anymore? Is it possible my dreamy bedroom eyes won’t make it to the 100th generation?
If you genuinely have dreamy bedroom eyes, then those will probably persist for quite a few generations, and might even become the default for humanity as a whole. If, on the other hand, your eyes are of merely normal seductive quality, then it’s a crapshoot.
The answer will be hugely different if we’re talking about “any” of your genetic material, or specifically about the, oh, handful or so of genes which code for your ocular dreaminess.
I didn’t take the OP’s question as him wanting to become his own predecessor.
What if he waited until his natural predecessor was born and did the deed after that; likely an adulterous situation… He would end up with a great-great auntie or uncle that has a bunch of his DNA.
If we’re not talking about the problems of becoming your own literal grandpa, the match between you and your grandmother are no closer than the one between first cousins, which is legally/socially approved in many localities. There may be a slight increase in the incidence of the expression of hereditary diseases, but not strikingly so.
The real effects of inbreeding come when you have repeated pedigree collapse. If your parents and aunt and uncle were also first cousins, marrying your first cousin means your offspring only have 4 great-grandparents instead of the expected 8–which is as close as a sibling mating.
I forget which Heinlein book it was, but in one of the later stories Lazarus Long ends up with two “daughters” Lazi and Lupi who are genetically identical to him except that they don’t have a Y chromosome. The two young women convince him to have a threesome with them by saying it’s basically masturbation (hah!) but also they point out that inbreeding is only bad if it reinforces bad recessive genes and the evidence suggests that Lazarus doesn’t have any of those to reinforce. Then he goes back in time and has sex with his own mother. RAH was a weird person.
It’s worth noting that, in large populations of cats and dogs, this sort of thing happens regularly. Animals end up mating with their own siblings or parents no more and no less frequently than anyone else in the colony, and that generally doesn’t produce terrible effects. In a pride of lions, the alpha male will have no reluctance to mate with his own daughters. But when humans do this sort of thing, it’s usually not accidental, it’s done on purpose. For example, trying to keep the family tree of the royal family from including any peasants. THAT’S when you run into trouble.
Well, remember your 100th generation descendant has to get their eye genes from somewhere. So there’s certainly a positive chance they’ll get one from you. In fact, assuming you do end up having a 100th generation descendant, the odds of them getting a particular gene from you have to be at least one in 7 billion or so (based on the current world population). Some quick analysis and very reasonable assumptions could probably get the odds down a lot farther.
That’s leaving aside whether the gene mutates between you and them. Up to you whether that would be the “same” “gene” or not, if it’s a direct copy from yours but with a copying error along the line.
Now, if your bedroom eyes are the result of the interaction of multiple genes, then things start getting much more ugly, since you’d need the 100th generation-vedder to get all of the appropriate genes, exponentially worse odds the more genes are involved. And of course, you’d need to also cut the odds for the chance of a mutation that changes things bedroom-wise.
[And of course, this is all based on the assumption that humans are going to continue biological mating with random meiosis, and no genetic engineering. Not something I’d really expect 100 generations from now, but we can only go with what we know]
People like Kurzweil want to mate with computers now, and Gates wants to kill 95% of the population, so, nothing will exist in 100 generations from now except solar powered computers with downloaded human brains.
Also note that, if you have any 100th generation descendants, you’ll likely be an ancestor of lots of people if not most people, and you’ll likely show up in multiple ancestor slots for a particular person.
Don’t forget “Time For The Stars” where IIRC the implication is that after getting back, he will carry on with his (greatgreat?)granddaughter.
Two siblings get a random selection of the genetic material of their parents, so they will be 50% match typically. However, each child of those siblings will only get half (typically) of the genetic material; but their choices too are independent. Child AA of Parent A may get say, 25% of what came from the grandparents and matches parent and uncle/aunt B. Child BB will get a different set of 25% from that matching 50%, so they will in fact only (typically) match AA to BB about 12.5%.
His great-grandniece, the great-granddaughter of his brother. Although since his brother was his identical twin, genetically she’d be the same consanguinity as his great-granddaughter.
Exactly. If that 100th-gen descendant had completely unique ancestors in this generation, that would be 2^100 ancestors today, but there are only about 2^32 people alive today.
So even if every single person alive today had descendants which interbred such that every signle person alive today was an ancestor of that 100th-gen-vedder, then Happy would still on average contribute 1/7 billionths of their genes.
Also consider that, 100 generations hence, you’ll probably have a lot of descendants. The odds of any particular one having any particular gene from you is slim, but the odds of any particular gene of yours living on in any of them are pretty good.
