What does the sentence 'that frees up Mother Nature to tinker around with ~' mean?

Question

Please, look at the last sentence in the passage. What does 'that' refer to? And the last sentence evades me. What does the sentence mean?

But here's the key point: Your brain doesn't know, and it doesn't care, where it gets the data from. Whatever information comes in, it just figures out what to do with it. And this is a very efficient kind of machine. It's essentially a general purpose computing device, and it just takes in everything and figures out what it's going to do with it, and that, I think, frees up Mother Nature to tinker around with different sorts of input channels.

Ted Talk - David Eagleman: Can we create new senses for humans?

Answer 1

"That" here refers to the nature an efficincy of the brain which was mentioned just previousl, specifically to:

...it just takes in everything and figures out what it's going to do with it ...

The speaker is saying that because the brain is an efficient computing mechanism, and because the brain operates on information without caring what the source is, different kinds of sensor input channels can be trie without needing to rework the organization of the brain as a whole.

One might argue with this statement, but that is what the speaker is saying.

By the way "mother nature" here is a personification of nature or the way the natural world operates.

Answer 2

I would say @David Siegel is correct, looking at the passage altogether, but in terms of the function of the word "that" in the sentence, I would point you to the beginning of the sentence. Here "that" refers to a fact or statement, as David quoted, so it is basically

that fact frees up...

or

the fact that it (the brain) is essentially a general purpose computing device, and it just takes in everything and figures out what it's going to do with it, frees up...

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As for the last sentence in all, written differently it is simply saying that the fact this is how the brain works, allows nature to try different kinds of inputs.