And were you aware that your trend broke down 30,000 years ago, and the brain has shrunk?

Yes. ("Dataset: all measurments of moninin cranial capcity available in the literature as of September 2000, for skulls older than 10,000 years old").

Bigger can be better when it comes to smarts.

It was part of a overall argument that humans have probably been getting smarter for the past few million years. And that this trend had nothing to do with the availability of fossil fuels or iron until perhaps very recently. It seems likely that this would have continued in their absence. And it seems likley that bigger brains would translate into better tools and more complex social organisation as they tended to have in eons past.