Incidentally, even if there were no information showing that abilities/ambitions were different, it would not be reasonable to assume they were the same until proven otherwise.
But we're not doing this a priori (unless you're some kind of cave-dwelling hermit who'se never seen another man or woman). I certainly haven't noticed any detectable difference in male/female intelligence in my own experience.
In general I try not to use a sampling of people different from the general population, filtered through my own personal biases, to draw conclusions like this.
Further, your inability to see a detectable difference might simply be due to a lack of a margin between the two groups. Humans are great at separating groups, they are not so great at detecting small differences between groups.
We're just talking about default assumptions here, so I'm not sure what you're getting at. Of course my default assumptions based on my own personal experience might be wrong; that's why they're just defaults.
>Humans are great at separating groups, they are not so great at detecting small differences between groups.
Is this actually true? It seems like a bit of a sweeping statement, and I'd be surprised if you have any hard evidence to back it up. Also, the observed inequalities between men and women are currently quite large, so it seems unlikely that very small differences between men's and women's abilities could explain them.
http://en.wikipedia.org/wiki/Sex_and_intelligence
Incidentally, even if there were no information showing that abilities/ambitions were different, it would not be reasonable to assume they were the same until proven otherwise.