Comment by doubleunplussed

I just mean that the existence of the human brain is proof that human-level intelligence is possible.

Yes it took billions of years all said and done, but it shows that there are no fundamental limits that prevent this level of intelligence. It even proves it can in principle be done with a few tens of watts a certain approximate amount of computational power.

Some used to think the first AIs would be brain uploads, for this reason. They thought we'd have the computing power and scanning techniques to scan and simulate all the neurons of a human brain before inventing any other architecture capable of coming close to the same level of intelligence. That now looks to be less likely.

Current state of the art AI still operate with less computational power than the human brain, and they are far less efficient at learning that humans are (there is a sense in which a human intelligence takes a merely years to develop - i.e. childhood - rather than billions, this is also a relevant comparison to make). Humans can learn from far fewer examples than current AI can.

So we've got some catching up to do - but humans prove it's possible.