Life's Other Secret: The New Mathematics of the Living World

This book is about biomathemetics for those of us who didn't know we were interested in biomathematics. Stewart teases us into the subject by exploring different contexts for the question of "What is Life?". This leads to explorations into how life is shaped by the properties of physical laws. The book focuses on abstractions. Stewart talks about ideas, but chooses not to go into much detail. Many of the illustrations have no explanations, and some have errors. The ideas are all clearly related, but they are never really tied together in the book. I think this was intentional. I think Stewart is hoping that the theme of the book will emerge from the ideas. If he had tried to state the theme as a conclusion that tied the ideas all together, the theme would belong to the author. He wants the theme to belong to the reader, and so he let's us come to our own conclusions. This leaves you with an unfinished feeling, but there are lots of good references (I especially like his annotated further reading section). I feel wiser for having read this book. The most confusing part of the book comes from using the name "math" to describe the language of numbers and as a notation for describing symmetries in the physical universe.

Stewart begins his book by telling the reader:"I am going to try to convince you that as wonderful as genes are, they are not the whole answer to the question of life. More radically, I am also going to try to convince you that a full understanding of life depends upon mathematics."Basically, Stewart believes that scientists have overemphasized genetics and ignored (or at least under emphasized) the role of what I'll call large-scale or macro rules of physics and chemistry and the comparatively simple mathematics that describe them. For example, a molecular biologist might see a striped shell and wonder which genes caused them. Stewart would be more inclined to ask if there isn't some sort of chemical diffusion equation that leads to the stripes without them being specifically encoded in the genes. The point is that DNA may not need to encode much detail in many cases because the detail arises spontaneously out of macroscopic laws.Stewart has studied at the Santa Fe Institute in New Mexico. Other prominent scientists associated with the Institute are Murray Gell-Mann and Stuart Kauffman. Kauffman, in particular, has conducted studies regarding emergent properties of self-catalytic systems and you can see the influence of his thinking in much of Ian Stewart's book (see Stuart Kauffman's book "At home in the universe, the search for laws of self organization and complexity").The book begins with discussions relating to the nature of life and musings about DNA and replication. It's interesting to see the line between life and non-life blur under Stewart's prose. Chapter three discusses the emergence of DNA, possible roles played by clay platelets, and the idea that DNA might be just a frozen accident - the molecule was picked because it evolved first and created an environment in which no others could get a start once DNA was established.Chapter four is called the oxygen menace. There is an interesting discussion of how prokaryotes might have evolved, created oxygen as a poisonous byproduct, oxygenated the atmosphere, and then evolved into eukaryotes to capitalize on a more efficient method of generating energy by burning fuel using oxygen in the new atmosphere. This chapter has some interesting stuff on how cells move using the cytoskeleton and microtubules. I also enjoyed the description of slime-mold colonies and how they illustrate the possible manner in which larger organisms evolved from cooperative colonies of less complex life forms.Chapter five is titled artificial life, but much of it deals strictly with the process of evolution among very un-artifical forms. There is a discussion about the famous finches on the Galapagos Islands and how they stimulated Darwin to understand how species evolve. There is also some interesting material on numerical taxonomy, evolutionary taxonomy, and cladism. Finally, the end of the chapter distills the discussion into general principles of evolution and how simple computer programs (artificial life) can illustrate many of the patterns we see in the real world among living species.The first five chapters are really just background information about the first life on our planet, the evolution of DNA, and general principles of evolution. Stewart's real thesis (and the real fun) begins in chapter 6 with flowers for Fibonacci. Ever wonder why the seeds in a sunflower spiral the way they do? Ever wonder why there are the numbers of petals you find in flowers? Chapter 6 has the surprisingly simple answer, and it doesn't require lots of information encoding in DNA sequences, either.Chapter 7 is a little more controversial than chapter 6. It attempts to show that patterns in living organisms might not be specifically encoded in DNA, but might result from gradient chemical reactions and diffusion in some species. In other words, DNA only needs to encode the production of the right chemicals at the right time and macroscopic rules using rather simple mathematics do the rest.Chapter 8 deals with speculation about sexual selection and how it relates to such things as the peacock's tail. In this chapter Stewart argues that in many instances the thing that is being selected is actually symmetry. Asymmetry can be a sign of a damaged or defective organism. The thing I enjoyed most from this chapter was the discussion about common hallucinations and how they might result from the way simple plane waves in the visual cortex map into our retina.Chapter 9 was my favorite. It describes hypothetical harmonic generators that work together in various relative relationships of phase and attenuation to produce the natural gaits of quadrupeds and even bipeds. Stewart has done original work in this area, and so this chapter has some of the most insight and technical backup. I've often wondered about this myself and contemplated the possibility that such natural harmonic generators might be somehow related to the tendency of our species to develop certain musical beats and to naturally move in rhythm with them.Of course you will want to read chapter ten, which shows how rather simple rules can lead to rather complex looking spider webs. And don't forget to read chapter 11 which discusses the complex interrelationships of reefs, along with some rather interesting information regarding Von Neumann's amazing insights.This isn't a book on mathematics - it's a book about how mathematics applies to biology. And it's mostly qualitative. There are no mathematical equations, for example.Overall, I think this is a first-rate book. It's well written, engaging, has a complete index, copious notes, good figures, and brilliant color plates that I especially appreciated. You don't have to agree with everything Stewart has to say, but I think you will find his arguments intriguing, thought provoking, and stimulating regardless. If you love life and mathematics, this book should be in your library.Duwayne Anderson, March 18, 2000

In Life's Other Secret Ian Steward contends that DNA ain't all there is to living things - that life is as much about the complex unfolding of dynamic systems as it is about the information encoded in your genes.Sounds plausible to me. Is Steward right? Dunno. But at least I know what the questions are, which is the first step.What I do know is that this is an interesting, well written and well argued book.

Life's Other SecretThe New Mathematics of the Living Worldby Ian StewartThe secret that this book explains is that although we have come to believe that genes are the basis of all life they are only one part of it. Genes are the building blocks but there may be underlying mathematical principals that govern how the blocks are put together. When you consider that mathematics is the study of structure and pattern you can start to see how this relates to the biological world. Nature displays many example of patterns. But why? Are the organisms following some mathematical law? Take for example the spiral pattern in the seeds of a sun flower. This pattern, in fact, follows the Fibonacci sequence - one spiraling clockwise and the other counter clockwise. A Fibonacci sequence (named after the guy who discovered it), goes like this:1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144...Each number is a sum of the previous two- 3 + 8 = 13.So, these spirals are quite beautiful, but why spirals? Why not concentric circles, or squares or random patterns? What biologists have found, is that, this pattern is the most efficient way of packing as many seeds as possible into the head of one sun flower. So how do you get from a sequence of numbers to a spiral? This involves the "golden number" or "golden angle" of 137.5 degrees and the ratio of one Fibonacci number to it's neighbour. This led me to wonder about spirals. Why are spirals important in Celtic art? Why do we see spirals when we hallucinate? (Just like in the cartoons when the mouse hits the cat on the head...).The sun flower seed patterns is just one small example of the many topics covered in this fascinating and extensively illustrated book. There lots and lots of ideas to exercise your brain - why are leopard spots different from jaguar spots? How do fish and birds all turn at once? Do crowds of people make patterns? This book may stimulate your mind - open your mind to thinking about very interesting things - although at times it's frustrating, leaving you feeling that you missed something along the way.

Could be the most interesting, informative and valuable book you'll ever read.