CHAPTER 33

Pioneer of artificial life

margaret a. boden

A

lan Turing’s 1952 account of ‘The chemical basis of morphogenesis’^1 pioneered the

use of reaction–diffusion equations in explaining the origin of bodily form. This

exciting paper showed how it is possible for various familiar biological structures

to develop by referring to chemical ‘morphogens’ whose actual identity was still unknown.

Some forty years later, his work began to inspire research in computer graphics, artificial life,

and structuralist developmental biology: the follow-up had needed to await huge advances in

computer power, computer graphics, and experimental biochemistry. Turing’s unpublished

mathematical notes found after his death are still not fully understood: they very probably

contain further insights into biological form.^2

Introduction

In 1794 the Romantic poet William Blake asked a deep question:^3

Tyger! Tyger! burning bright

In the forests of the night,

What immortal hand or eye

Could frame thy fearful symmetry?

. . . Did He who made the Lamb make thee?
The answer was a mystery. But Blake apparently assumed that it must involve some super-
natural power—perhaps the Christian God. Most of his contemporaries would have agreed
with him.
Even 150 years later, in the middle of the 20th century, this answer was still widely accepted.
But by this time the study of embryology had progressed enough to suggest that the marvel-
lous development of an undifferentiated egg-cell into an embryo of increasingly complex form
could in principle be given a scientific answer. Moreover, embryologists believed that the answer
would refer to chemicals—called ‘organizers’—that cause successive changes in the cytoplasm
as the egg gradually develops into organs of differing types.