Specifically, what amino acids are you referring to? I'm not a vegan or knowledgeable about nutrition and my wife's not around to confirm/debunk/clarify your claim for me.
If we're talking on a scale of hundreds/thousands of years with "recently" then the same is true for protein and fat; our ancestors didn't have supermarkets, planes and trains and boats capable of transporting food thousands of miles across countries and oceans. Given that our brains require sugar to function, however, it's a safe bet that we've been eating carbohydrates pretty consistently throughout time (although it's also likely that, historically, we had a much more varied diet than the standard American diet).
Regarding fats--if you change "need" to "can use", then you're correct. As it is, you're mistaken: http://www.fi.edu/learn/brain/fats.html#fattyacids (if you don't feel like following the link: you can get essential fatty acids through vegetables, nuts, and various plants/plant oils.)