1062 THE STRUCTURE OF EVOLUTIONARY THEORY
it is notoriously difficult to measure differences in genes that vary only in the timing
and amount of their products in ontogeny, while genes that code for stable proteins
are easily assessed)."
Barely 20 years later, this statement reads like a quaint conceptual fossil from an
"ancient" time of crossbows and arquebuses, when we could only reconstruct the
anatomy of genes from their protein products (and could not recognize regulatory
genes that did not deposit such results in explicit flesh and blood). I therefore
succumbed to the necessity of technical limits and ended a long book with the
weakest of conclusions—a future hope, however heartfelt and (in retrospect)
accurately surmised: "I believe that an understanding of regulation must lie at the
center of any rapprochement between molecular and evolutionary biology; for a
synthesis of the two biologies will surely take place, if it occurs at all, on the common
field of development" (Gould, 1977b, p. 408).
Now, as I begin this chapter in the summer of 1999,1 can only express both my
joy and astonishment at a subsequent speed of resolution and discovery that has
sustained my predictions, but also made my earlier book effectively obsolete, not
only within my own lifetime, but during my active mid-career. The field of
evolutionary developmental biology (known as "evo-devo" to practitioners), while
still in its infancy, has invented the tools—and already cashed out a host of stunning
and unexpected examples—for decoding the basic genetic structure of regulation, and
for tracing the locations and timings of regulatory networks in the early development
of complex multicellular creatures.
But this very pace of growth and excitement presents a problem for a book like
this, with a "lead time" measured in months to years, rather than the professional
journal's weeks to months or the popular press's days. The discoveries of deep
homology and pervasive parallelism among phyla separated for more than 500
million years continue to accumulate at an accelerating pace, based on
methodological refinements and extensions, in both speed and accuracy that could
hardly have been conceptualized even a decade ago.
This situation places me in a quandary (although I could hardly imagine a
happier form of puzzlement). The data of evo-devo constitute the largest and most
exciting body of novel empirics to support this book's general thesis. Since I have
tried to provide thorough overviews of empirical documentation for other central
elements of my overall theory, I should now be tabulating and evaluating these cases
of deep genetic homology in extenso. But I am hoist by my own petard of emphasis
on appropriate scales. The data of evo-devo accumulate and improve at such a pace
that any thought of a "review article" written more than two years before anticipated
publication can only be regarded as absurd. In other words, this book's timescale of
production must be labeled as geological compared with a pace of discovery that can
only be measured in ecological time.
I will therefore adopt the following strategy as appropriate to the circumstance. I
will exemplify the best and most informative of current empirical cases, but I ask
readers to heed the following label of warning: "I wrote this