We think, that is a fact.
Therefore, there is a function capable of transforming information into "thinked information", or what we usually call reasoning. We know that function exists, because we ourselves are an example of such function.
Now, the question is: can we create a smaller function capable of performing the same feat?
If we assume that that function is computable in the Turing sense then, kinda yes, there are an infinite number of turing machines that given enough time will be able to produce the expected results. Basically we need to find something between our own brain and the Kolmogorov complexity limit. That lower bound is not computable, but given that my cats understands when we are discussing to take them to the vet then... maybe we don't really need a full sized human brain for language understanding.
We can run Turing machines ourselves, so we are at least Turing equivalent machines.
Now, the question is: are we at most just Turing machines or something else? If we are something else, then our own CoT won't be computable, no matter how much scale we throw at it. But if we are then it is just matter of time until we can replicate ourselves.