If in the future there was an evolved human race with around 10% more?
Interesting question. I think the simple, uninteresting answer is yes. However in Homo deus (or possibly Sapiens) Yuval Noah Harari explains that our brains have actually gotten smaller since we abandoned the hunter-gatherer lifestyle; the suggestion is that we don't actually have as much to think about now as we used to 50k years ago. There are a few caveats to this: Number of neurones is not as important as the number of connections between the neurones (I believe this broadly correlates to the extent that the brain is folded - mammal brains have far more gyri/sulci than reptile brains) - but this is hard to glean from ancient bones. It might well be that this trend has reversed since the start of the information age - changes would be too slow and subtle to see over just a couple of generations. The advent of mind-computer interfaces and general AI may very well lead us to a singularity event (as predicted by Kurzweil I believe) - a melding with technology that self-advances at an accelerating rate to the point that we can't imagine what life will be like on the other side.