I personally find any argument that relies on our lack of understanding of complex systems and emergence to be on shaky grounds at best and a fallacy at worst.
[1]: https://www-rohan.sdsu.edu/faculty/vinge/misc/singularity.ht...
One could wonder if it didn't already happen with the economy.
In a way, talking about these kinds of "meta-intelligences" is kind of a point-of-view thing. It depends on the abstraction level you use. You can look at an ant and think about it as an individual insect, or realize that it's just a tiny, specialized cog in an intricate machinery of a colony - a colony that kind of behaves like an individual animal. Similarly, at what point our day-to-day interactions with other people, aggregated over the entire population of the planet, start to resemble a planet-sized organism doing weird self-regulation stuff? What's the difference between saying that "the market decided" and saying that a low-level decision was made in a part of the planet's brain?
Abstractions are weird this way.
"accelerationism" otoh is a clear and interesting concept.
Which if the author is right and our brains have already been shrinking means that within a few hundred years, there won't be any humans left - just "higher intelligence".
I've never understood people's naivety thinking we're always going to be at the top of the evolutionary ladder. At some point, we will be replaced and humans in whatever form they take now will cease to exist in the very near future.
No, it really doesn't. Even if the extrapolation was correct - which is dubious at best - losing 15% of brain over 10 000 years certainly wouldn't mean "no humans within a few hundred years".
If we cease, we had a good run.