I was very into the idea that the technological singularity would happen when total computation was at 10^15 computations per second, inspired by Singularity University that I read about in 2009 in a Nature paper magazine while eating breakfast (subscribed to it, that was around the time the app explosion began. )

Then, 4 years ago, I came across the idea that neurons are not transistors, instead, they contain "resonance computers" in the form of microtubules, that microtubules are computers. Having been very interested in microtubules since 2009 as well, when I started med. school, I was sceptical at first (that's not how microtubules work!), and then gradually opened up up to the idea.

It makes a lot of sense that the cell would have evolved a computer, and if it has, then it makes a lot of sense that neurons would co-opt it.

If the microtubule hypothesis is true, then that would put the brains capacity far beyond 10^15.

Notes

In bacteria, proto-microtubules are composed of 5 tubulin threads, rather than 13, and so would have less computational capacity,
Microtubules in Bacteria: Ancient Tubulins Build a Five-Protofilament Homolog of the Eukaryotic Cytoskeleton