You missed the terrifying aspect. It's not terrifying that general intelligence emerged from optimizing for reproductive fitness specifically, it's terrifying that general intelligence emerged while nature was stumbling around randomly in the dark trying to optimize for a complete unrelated property.
Guess what we're doing with machine learning?
General intelligence didn’t poof into existence it happened over half a billion years and even then it came from fungi which is itself an intelligence.
Why millions of years? Do you agree or disagree that humans can develop technology faster than nature could evolve it on its own? It took maybe 70 years for computers to go from not existing, to matching humans on visual recognition tasks.
As you just acknowledged, it took nature at least billions of years to evolve humans. Is not focused technological development obviously orders of magnitude faster at evolving intelligence than nature? Does it not then follow that general intelligence is a lot closer than an argument based on natural evolution might imply?
What exactly is not logical about this argument?
Personally I figure that once you have a complex enough system with feedback regulation and self-preservation, something like general intelligence occurs spontaneously through the normal mechanisms of evolution (probably more than once in different kingdoms) because it provides a heritable survival edge.
I agree that the simplest properties of neural networks are an emergent property of multicellular life.
For a while I ran a project that ran a (scientific) binary on every Google machine in production using all the idle cores on the machine to do protein design (it worked!). At the end of the project we seriously considered making the binary instead a learning system that had access to 'sensors' (IE, signals from Google production machines) and 'outputs' (the ability to change production parameters) and just let that run autonomously. I figured Google prod is one of the few computational/networking systems with enough inherent complexity and resources that spontaneously emergent general intelligence was not inconceivable. However, the project was deemed too risky by SRE, rightfully so. Not because of emergent intelligence but emergent disruption to serving ads.