I'm not too sure it's "late". At first I thought the same as you, but i think environment varies so much between us I think it is something else. Personally I think so many more people are breeding now,before we had little information about a gestation "range" and I think now we are figuring out a better idea of of norm. 5 years ago who is to say where the info was coming from, and lot of people were hush hush about it. Maybe I'm wrong, I'm not that deep into it just my 2 pennies, if you are right and there is some sort of global factor causing longer gestation I would see that as very important to research.