First of all, before diving into the mechanics of Polymorph Any Object, make sure you are reading a version with the applicable updates and errata. d20srd.org is one place that has correctly applied them.
Then, we must look at how Polymorph Any Object is connected to the other spells of its line. Turns out, it inherits from Polymorph, which again inherits from Alter Self.
Then, let's go through...
First in line: Alter Self. Alter Self grants:
- Mundane movement
- Natural Armor
- Natural Weapons
- Racial Skill Bonuses
- Racial Bonus Feats
Then, from Polymorph, we additionally gain the new form's:
- Extraordinary Special Attacks
Finally, from Polymorph Any Object, we gain:
- Intelligence! Beware, this can leave you dumber than you were.
So what happens to our human?
The human gains the qualities of the new race listed above.
The human's classes are not affected by any stage of the morph. This is made explicit in Alter Self:
Your class and level, hit points, alignment, base attack bonus, and base save bonuses all remain the same.
Humans are rather scarce when it comes to racial features to lose, with the exception of the bonus feat and skill points. They are maybe lost. It is not made abundantly clear in the rules what the human's bonus feat and skills really are. The 3.5 FAQ calls them an extraordinary qualities, which we lose as part of Alter Self:
You keep all extraordinary special attacks and qualities derived from class levels, but you lose any from your normal form that are not derived from class levels.
I will leave it to you to decide whether the FAQ is right on that point. I see little in the way of rules to support the claim.
Finally, Level Adjustment. No one knows how that is affected by the morph. It is not addressed by the rules. Despite how trivial it is to use PAO to permanently change into a related race, level-ups when so morphed just aren't covered. Does that mean it's unchanged underneath your new form? Does
[Polymorph Any Object] changes one object or creature into another
mean that the change really is all the way down to the Level Adjustment? I don't know.
Discuss it with your DM. And above all else, remember that Polymorph is broken.