Well there is this theory of what happened:
There was a war before Ash was born in which Lt. Surge was in, and where he says his electric pokemon saved his life. So perhaps Ash's father was killed in that war, and the lack of MIddle-Aged man is another evidence.
So Ash's story is the beginning of a peace after the war have ended.
I very much like this theory. It's quite brilliant and fits together with the Ho-Oh theory which seems to have been misunderstood here, at least by the thread creator. The belief is that Ash's father had reincarnated as Ho-oh, not that Ash was fathered by a freaking bird. XD
Remember the legend which the Silver Conference Torch is based upon? There was once a great war between both humans and Pokemon with several casualties on both sides. Perhaps this is the war Lt. Surge was involved in. The storyteller had only said 'Long ago' which is not precise meaning it could very well have taken place while Ash was in his infancy. Ho-oh had suddenly appeared and destroyed all weapons with it's rose colored flame which ceased the war. So when Ash's father possibly perished in this same war perhaps he returned as that Ho-oh and is the legendary savior.
It certainly would be fitting the child of such a man one day rushing in between the attacks of the world's two strongest Pokemon to cease yet another type of war as Ash did in 'Mewtwo Strikes Back'.
There's also another way this can be viewed; it's outrageous and way over glorifies Ash but I have to admit that it does have some fitting aspects.
This theory reverses the Ho-oh belief. There is another story which tells of Ho-oh or perhaps a
Ho-oh(so the one which stopped the war could be a different one) which had lived and vanished from earth 300 years ago when it reincarnated Entei, Suicune and Raikou after they perished in the fire which destroyed the original Tin Tower. "Ho-oh's fierce anger will only melt away when the hearts of Pokemon and humans meet as one. Ho-Oh sent three pokemon down to earth to observe us...the legend says that humans trying to steal the power of Ho-Oh and all pokemon causing the great fire in the tower, three pokemon were caught in the flames unable to escape on time. Ho-Oh watched in sadness and disgrace."
- For Ho-oh The Bells Toll
It sent the reincarnations of the three pokemon who had perished in the Tin Tower to watch over the earth for the time when Pokemon and Humans would exist together in harmony.
But in wasn't happening, the hearts of humans continued to look upon Pokemon with greed and selfishness as centuries went by. So perhaps Ho-Oh decided that it would need to take further action. So somehow it brought forth a child to the earth which would being the creatures together. There are a number of possibilities such as that it descended to earth in human form (maybe even because Ho-Oh as well is not it's true form) or incarnated a man to father this child or the child itself as it rose it's slaves from the ashes of the tin tower.
Think about it, Ash was the prophesied 'Chosen One' in the second film 'The Power of One', in which he and only he could bring peace between Moltres, Zaptos and Articuno when they had broke out in battle with each other, a battle which would bring destruction upon the earth.
I've not seen all the films but Ash does something pretty huge and profound in most does he not? He always even in the simplest of episodes stands up for a world where Pokemon and Humans stand together does he also not?
A rainbow in the sky is said to be a sign of Ho-oh, that it is watching over the earth continuing it's wait. Doesn't this sound like God? Taking action against the earth's sin, the rainbow at the end of Noah's Ark? Personally I am not heavily into all that myself but it does seem to have a relation does it not?
Like I said though outrageous. If this were actually true I'd say "give me a break!"
The first scenario is much better.