You're wasting your time.
Maybe these chromosomes weren't fused at all?
Otherwise you would have to explain why three of the six children had normal chromosomes (which is the implication here)."
Sorry, in the interest of brevity (which I've already grossly abused) in post #174 I provided you only a link, not quotes from it, but that does explain at least some of what you say:
From 2013, a less optimistic view of reproductive problems related to chromosome fusing:
- "You are correct that like other apes today, ancient humans had 48 chromosomes, and that the exact same mutation (fusing of the same two pairs of chromosomes) must have occured in both a male and female mating pair in order to produce the first human with the modern number of chromosomes, 46.
- (A) {12} & {13, 12+13}
- (B) {13} & {12+13}
- (C) {12, 13} & {12+13}
- One is a 'normal' {12, 13} set, which would produce a 'normal' ancient human with 48 chromosomes when combined with a 'normal' egg.
- The second would produce a human with 47 chromosomes, like the father himself, when combined with a 'normal' egg.
The observation that such an event is very unlikely is, in fact, a significant genetic clue that the human species almost went extinct at one point!
Here's what happened: Specifically, the 12th and 13th chromosomes of the ancestors of modern humans (the same chromosomes in apes today except humans) fused to become the 2nd chromosome in modern humans.
A chromosomal fusion in one particular individual doesn't necessarily impact health, but it may reduce their fertility.
About a million years ago, an ancient human (let's say a male) was born with a fused 12th and 13th chromosome.
Thus, he had 47 chromosomes, with three of them being 12, 13, and a 12+13 fusion.
During meiosis, there are three equally likely ways to partition those three chromosomes into two groups:
Method C produces two healthy sperm cells:
"Thus, two-thirds of the children produced by this 47-chromosome man would die even before birth, one-sixth are 'normal' 48-chromosome humans, and one-sixth are healthy 47-chromosome humans with the same fertility issues as the father.
Of course, under normal circumstances, natural selection eventually weeds these odd-chromosomed humans out of the population due to their reduced fertility.
However, if a 47-chromosome man mates with a 47-chromosome woman (with the same two chromosomes fused), then 1/36 of their children could viably have 46 chromosomes.
Furthermore, now that these children have an even number of chromosomes, the fertility issues no longer exist if these descendants continue to mate with others with 46 chromosomes.
The chances of two people with the exact same fusion mating is extremely small... unless they are closely related.
And that's almost certainly what happened about a million years ago:
For some still unknown reason (possibly climate change, disease, famine, etc), the world human population was reduced to only a few thousand individuals (or perhaps even just a few hundred) scattered around Africa.
Thus, there was much inbreeding in these small isolated groups, creating genetic bottlenecks where rare genes or genetic features (such as having fused 12-13 chromosomes) could become widespread."