poly: Nanomedicine and cell types

I've been reading Nanomedicine, by Robert Freitas, a very detailed and
thorough examination of the potential impact of nanotechnology on medical
treatment. In my opinion this book is as important and fundamental as
Drexler's Nanosystems, and more up to date. Despite the medical theme,
most of the first volume (two more are in the works) deals with relatively
fundamental abilities and limitations of nanotech which would apply in
a wide range of applications.

As an amazing gift, the entire book has been made available online at
http://www.nanosystems.com. This seems to be the complete text although
some of the pictures are still missing. This would be a good way to
try the book out and see if you like it before purchasing. Warning,
it starts off with a rather dry introduction to the history of medicine.
I'd skip on to chapters 3 and 4 to start getting the flavor of the book's
description and analysis of nanotech capabilities.

Reading ahead to section 8.5.2.2, I came upon a puzzling claim.
"Complexity theory and phylogenetic comparisons suggest that the maximum
number of cell types Ncell ~ Ngene^(1/2) = 370 cell types for humans
with Ngene ~ 10^5 genes."

I'm not sure if the "and" here means that these are two separate lines
of evidence pointing to the same conclusion, or whether one must combine
complexity theory with phylogenetic comparisons in order to derive the
square root result. In any case I am puzzled about what complexity
theory would have to say about it.

The statement is footnoted with two references: Stuart Kauffman's book
"The Origins of Order", and a technical paper by Kauffman.

Is anyone familiar with the logic which leads to the conclusion that
the number of cell types would be roughly the square root of the number
of genes?

Thanks,
Hal
Received on Mon May 29 20:13:39 2000