From scratch

Internet arguments, the best kind of arguments! Transhumanists rallied to defend Kurzweil after PZ Meyer's harsh assault on his blog post "Ray Kurzweil does not understand the brain". Kurzweil himself responded with a thoughtful analysis.

The argument centers on one question: "how much information is needed to (reverse) engineer a brain?" Kurzweil guesses about 50 megabytes. Myers says that 50 meg is not enough because A) brain function is very complex and we don't understand most of it; B) the brain is made of billions of cells that all interact with each other, with proteins and other chemicals, and those interactions can not be compressed digitally to a small size.

Point A is silly: we don't need to know how something works to build it. Even Kurzweil made this mistake in his reply. The Wright brothers, who built the first airplane, were high school drop-outs and bicycle mechanics; they probably have never heard of Bernoulli's principle of fluid dynamics, nor did they need to. The first humans who built boats did not need to know why they float. Mothers do not need to know how a brain works to gestate a fully-functional human brain (and the baby!) in 9 months.

For point B, Myer is attacking a strawman; he didn't see Kurzweil's full presentation and assumed that the claim was about an adult brain. Think of the distinction as the difference between an out-of-the-factory computer, and the one you have in front of you. The argument brings up a very good question though: how much information is required to build a brain from scratch? How long would that recipe be?

Let's look at how babies are made. Sperm meets egg to form a complete genetic blueprint. That's all that Kurzweil's analysis covers, and it brings us to 50 megs of data. How much more data goes into brain development between fertilization and birth? What about all the proteins and fluids and chemical gradients? Chemical change is slow, on the order of minutes at least. I'll guestimate around 1000 different chemicals and proteins in the mother's womb / blood, each of which can change its concentration in 10 minutes. That gives a bitrate of 2^10 (number of chemicals) * 20 (bits needed to describe gradient levels) / 2^10 (seconds) = 20 bit/sec. That times 9 months gives a total of 50 megs sent, through chemical signaling, to the fetus.

Does the fetus get information in any other way? There are no nerves in the umbilical cord, so the fetus's brain is not connected to the mother's in any way. The only other way for a fetus to gain information is from its own senses. Are the fetus's senses active? It would not see or smell anything. But what about touch and sound? 9 months of aural input would add up to a lot of data. Here, we have to limit the input to what is specified by the mother's biology; that means music is not required for brain development. What about the mother's heartbeat and breathing sounds? Maybe. But that repetitive noise only adds minimal amounts of data.

What about all the complex chemical reactions inside individual cells? They don't matter. Treat the fetus's brain as one complete entity; the amount of information in its design is equal to the amount of information that goes into it, either from the original gametes, or from the environment of the womb. Everything else, the fetus does on its own. From scratch means we don't have to look any deeper than chemicals and proteins and genes. Put these components together in this specific way: sperm + egg + chemical environment = healthy, functional baby. No quantum physics required!

Let's look computers now and compare; how much information is required to create the latest gadget?  The blueprint of the latest gen Iphone, I'm guessing, is about 10 meg to 100 meg (I've seen cpu design docs around 1 meg uncompressed). Well I can't build one with just the design blueprint; I need the right parts! Add the docs for CPU, LCD screen, antenna, etc. I'll still need the right machines to build all those things! Add blueprints for the machines and the factory. What about the materials? How do I get a hold of germanium? Add in mining equipments, refining processes, prospecting, transportation, etc etc. Where does this end? From scratch means we can just stop there. Sure, there's probably an entire library of physics and engineering books that outline the operating principles of mobile phones and computers, but that's not needed to build one. All we need is the chain of blueprints that will get us from rock to phone.