That's also interesting... I think the two ways of looking at it are equivalent, i.e. any pattern that satisfies one should also satisfy the other. (Only because the XOR pattern works both vertically and horizontally.)
What book?
won't have the problem of being acyclic
Should that be "cyclic"? I take it from Richard's post that "acyclic" is what we want.
It should be pointed out here that biological genuses, families, orders, and so on do not exist.
Yes, this is true of course.
What I was saying is that humans are the only living member of the Homo family
So was the claim "Humans are the only single species mammal" simply a claim that humans are the only mammal with their own genus? That's certainly not true, see http://en.wikipedia.org/wiki/Category:Monotypic_mammal_genera
The reproductive isolation can be genetic, or it can be simply geographical or habitual.
This is probably not relevant to our point, but Futuyma (2005) Evolution p356 defines reproductive isolation as "reduction or prevention of gene flow between populations by genetically determined differences between them" - i.e. it's not enough that they are geographically separated.
homo sapiens exist in one giant gene pool
This just seems to be a claim that the population size of our species is quite large. There are other species of mammal with large populations. Again, the relevance of any of this to sex-determination is rather doubtful.
None of the things you mention are likely to affect the sex determination system.
the only single species mammal.
The only what?
Could you direct me to the comparative analysis of Mammalian reproductive systems that discusses hermaphrodites in other species?
What I meant was that we can think about other mammals ourselves, and note that no other mammal species has hermaphrodites at significant frequencies. I had no specific research in mind.
there would be a decent size population of hermaphrodites able to develop a stable social station; if there were a stable hermaphrodite community their genes would spread
This depends both on a genetic cause, and also on hermaphrodites having equal fitness to males and females.
I think the intentional elimination of hermaphrodites has made a huge impact on the demographic of humanity, do you disagree?
Yes, I disagree, for the reasons I've stated. Other mammals have had no "intentional elimination", yet hermaphrodites remain at very low levels. So "intentional elimination" isn't the reason for the very low levels.
Also I don't think you can use the fact other gonochronistic mammals have not developed more sexes as a reason why humans would not.
Of course I can; humans aren't particularly special, at least not in relevant ways.
I don't think there's a prejudice against replying to old posts around here...
This fact though -- that monkeys are paraphyletic -- argues in favour of (not against) the view that the common ancestor of monkeys and apes was itself monkey-like...
If you think about when the "ape traits" must have evolved, it would be after the new-world monkeys had already diverged away. The common ancestor of monkeys and apes wouldn't have had them, but must have had those traits common to both old and new-world monkeys. It itself has to be basically a monkey.
(I drew out a phylogenetic tree for this but couldn't get it to format, alas...)