The first time I ever took a graduate math course, I did my term project on precisely this theory. Analyzed the PDE's, did some numerical experiments on it, gave a lecture on it. I had to tell my audience "Well, we think this produces tiger stripes and giraffe spots, but honestly we're just blindly guessing."
What a treat to read this! Shows that us mathematicians are often fifty years ahead of the times ;)
Hmm, I beleive conjecture is used when you are speaking about a potential theorem (i.e. something than can be mathematically proven to be right given certain axioms). This is a biological/chemical/natural theory, and is believed to be true given certain findings in some observed phenomena (i.e. statistics are involved in a certain way).
A conjecture is an assertion made on the basis of incomplete evidence. I'm not familiar with Turing's work in this area but if (as others have commented) he studied PDEs and that appear to mimic biological processes, yet did not find a definitive link, then the conclusion that a connection between the two may exist can only be described as conjecture.
Turing worked on a family of partial differential equations called "reaction-diffusion equations", and determined that for particular choices of the parameters, they produce phenomena similar to tiger stripes, leopard spots, and the like. One doesn't have to describe this in terms of biology; mathematically it is already interesting on its own.
But how much cooler is it that this can be observed by a visit to a zoo! He (or perhaps biologists who studied his work?) conjectured that some biological process behaved according to his equations, and therefore produced the behavior they model. However, until now, no one had ever found such a process.
My understanding was that Turing's theory of morphogenesis had already been shown to be correct in some cases in biology; they just didn't know it to be true in the case of tiger stripes.
In fact, they had shown it not to be true for some other striped animal (can't recall which one), which I think makes this discovery even more interesting.
We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called
reaction-diffusion, which has been proposed as a model
of biological pattern formation. We extend traditional
reaction-diffusion systems by allowing anisotropic and
spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion
systems to the needs of computer graphics by presenting
a method to synthesize patterns which compensate for the
effects of non-uniform surface parameterization. Finally,
we develop efficient algorithms for simulating reactiondiffusion systems and display a collection of resulting textures using standard texture- and displacement-mapping techniques.
I am quite surprised that such a simple question of why does a tiger have stripes (which kids are asking all the time) went so long unanswered. I wonder how many questions like this are there?
What a treat to read this! Shows that us mathematicians are often fifty years ahead of the times ;)