Wednesday, August 18, 2010

ray kurzweil does not understand the brain

Pharyngula | There he goes again, making up nonsense and making ridiculous claims that have no relationship to reality. Ray Kurzweil must be able to spin out a good line of bafflegab, because he seems to have the tech media convinced that he's a genius, when he's actually just another Deepak Chopra for the computer science cognoscenti.

His latest claim is that we'll be able to reverse engineer the human brain within a decade. By reverse engineer, he means that we'll be able to write software that simulates all the functions of the human brain. He's not just speculating optimistically, though: he's building his case on such awfully bad logic that I'm surprised anyone still pays attention to that kook.

Sejnowski says he agrees with Kurzweil's assessment that about a million lines of code may be enough to simulate the human brain.

Here's how that math works, Kurzweil explains:
The design of the brain is in the genome. The human genome has three billion base pairs or six billion bits, which is about 800 million bytes before compression, he says. Eliminating redundancies and applying loss-less compression, that information can be compressed into about 50 million bytes, according to Kurzweil.

About half of that is the brain, which comes down to 25 million bytes, or a million lines of code.
I'm very disappointed in Terence Sejnowski for going along with that nonsense.

See that sentence I put in red up there? That's his fundamental premise, and it is utterly false. Kurzweil knows nothing about how the brain works. It's design is not encoded in the genome: what's in the genome is a collection of molecular tools wrapped up in bits of conditional logic, the regulatory part of the genome, that makes cells responsive to interactions with a complex environment. The brain unfolds during development, by means of essential cell:cell interactions, of which we understand only a tiny fraction. The end result is a brain that is much, much more than simply the sum of the nucleotides that encode a few thousand proteins. He has to simulate all of development from his codebase in order to generate a brain simulator, and he isn't even aware of the magnitude of that problem.

We cannot derive the brain from the protein sequences underlying it; the sequences are insufficient, as well, because the nature of their expression is dependent on the environment and the history of a few hundred billion cells, each plugging along interdependently. We haven't even solved the sequence-to-protein-folding problem, which is an essential first step to executing Kurzweil's clueless algorithm. And we have absolutely no way to calculate in principle all the possible interactions and functions of a single protein with the tens of thousands of other proteins in the cell! Fist tap Dale.