Philosophy of Biology

DEVELOPMENT: THREE GRADES OF

ONTOGENETIC INVOLVEMENT

D. M. Walsh

1 INTRODUCTION

Viktor Hamburger [1980] famously claimed that developmental biology was left out
of the modern synthesis from its inception in the early 20thCentury. He didn’t
mean that some anti-ontogeny conspiracy met in some smoke-filled room and de-
creed that developmental biology should be excluded. At the time, developmental
biology was a discipline in good standing, and those who forged the synthesis were
well aware of it. Developmental biology was ‘left out’ simply because it didn’t
seem to matter much one way or another; it seemed to pose no threat, nor to
offer any great enhancement to the emerging orthodoxy. In Hamburger’s words,
evolutionary biologists came to treat development as a ‘black box’, a process that
played some contributory role in evolution, but whose details had little bearing
on the correctness or otherwise of the synthesis theory. So for much of the 20th
Century developmental biology languished as a relative outsider among biological
disciplines, an area of only marginal interest to evolutionists. It is only recently,
now that more of the details of ontogeny are understood, that biologists have had
cause to rethink the place of development in evolutionary biology. Developmen-
tal biology is now one of the most rapidly growing disciplines in biology. It has
witnessed enormous advances in the understanding of the mechanics — genetic,
epigenetic and environmental — of development in the last twenty years. It is
clear now that an understanding of the processes of development is of cardinal im-
portance to the project of explaining the mechanisms of evolution. Yet in spite of
this flourishing — or perhaps because of it — there is little consensus on just how
this newfound knowledge should impact our conception of evolutionary theory.
I attempt here to outline the space of possible roles for ontogeny in evolutionary
biology. I don’t intend to adjudicate — although I do have my preferences. It’s
an empirical issue which of the alternatives is most plausible. But I hope at least
to help shed some light on just what that empirical issue is.
One coherent possibility is that an understanding of the processes of ontogeny
should occasion no revision to the version of the modern synthesis theory we have
grown so comfortable with [Raff, 1996]. But there are others. I develop two other,
increasingly central, possible roles for the process of development in evolution.
These, by degrees, challenge the standard version of the modern synthesis. In

General editors: Dov M. Gabbay,
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Handbook of the Philosophy of Science. Philosophy of Biology

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