gould on dawkins

[Les Schaffer <godzilla@xxxxxxxxxxxxxx>]

there has been some brief discussion recently of the views on
evolution of Richard Dawkins.

While doing a little on-line reading this afternoon, i stumbled across
an interesting article by Stephen J Gould and Elisabeth A. Lloyd
entitled: Individuality and adaptation across levels of selection: How
shall we name and generalize the unit of Darwinism?

in particular, gould and lloyd speak of a disctinction between
replicators (Dawkins) and interactors (Hull and others):

<<<<< The central and contentious issue of causal agency in natural
selection -- does Darwin's process work on organisms (as Darwin
argued), on genes (as various reductionist accounts maintain), on
supraorganismal units, or on some or all of these legitimate
biological individuals simultaneously (as we and many others now hold)
-- has generated much confusion, arising not so much from dispute
about empirical matters, but from conceptual problems about the
nature, locus, and meaning of causality in Darwin's mechanism. In
particular, many biologists have mistakenly equated the need for
keeping a ledger of evolutionary changes through time with the task of
identifying causal agents of change -- a conflation of bookkeeping
with causality.

David Hull's important distinction between replicators and interactors
(27) helped to clarify conceptual and empirical issues at the center
of debates about units of selection. Hull modified Dawkins' concept of
a replicator to designate any entity that can serve as a basis for
copying itself. Hull's concept of interactor denotes an entity that
interacts directly, as a cohesive whole, with its environment in such
a way that replication becomes differential. For Hull, natural
selection then becomes "a process in which the differential extinction
and proliferation of interactors cause the differential perpetuation
of the replicators that produced them" (ref. 27, p. 318; cf. ref. 11,
pp. 317-318).
>>>>

abstract below, but the full article in HTML can be found online at:

http://www.pnas.org/cgi/content/full/96/21/11904?gca=96%2F21%2F11701&gca=96%2F21%2F11904&gca=96%2F21%2F12198&sendit=Get+All+Checked+Abstract%28s%29&;;

dat's a long link! if you have trouble navigating it, let me
know. also, a pdf version can be downloaded directly at:

http://www.pnas.org/cgi/reprint/96/21/11904.pdf

les schaffer

-----------------------------------------------

Vol. 96, Issue 21, 11904-11909, October 12, 1999

Evolution

Individuality and adaptation across levels of selection: How shall we
name and generalize the unit of Darwinism?

Stephen Jay Gould*, and Elisabeth A. Lloyd

* Museum of Comparative Zoology, Harvard University, 26 Oxford Street,
Cambridge, MA 02138; and History and Philosophy of Science, Indiana
University, 130 Goodbody Hall, Bloomington, IN 47405

Contributed by Stephen Jay Gould, June 2, 1999

        Abstract

Two major clarifications have greatly abetted the understanding and
fruitful expansion of the theory of natural selection in recent years:
the acknowledgment that interactors, not replicators, constitute the
causal unit of selection; and the recognition that interactors are
Darwinian individuals, and that such individuals exist with potency at
several levels of organization (genes, organisms, demes, and species
in particular), thus engendering a rich hierarchical theory of
selection in contrast with Darwin's own emphasis on the organismic
level. But a piece of the argument has been missing, and individuals
at levels distinct from organisms have been denied potency (although
granted existence within the undeniable logic of the theory), because
they do not achieve individuality with the same devices used by
organisms and therefore seem weak by comparison.  We show here that
different features define Darwinian individuality across scales of
size and time. In particular, species-individuals may develop few
emergent features as direct adaptations. The interactor approach works
with emergent fitnesses, not with emergent features; and species, as a
consequence of their different mechanism for achieving individuality
(reproductive exclusivity among subparts, that is, among organisms),
express many effects from other levels. Organisms, by contrast,
suppress upwardly cascading effects, because the organismic style of
individuality (by functional integration of subparts) does not permit
much competition or differential reproduction of parts from
within. Species do not suppress the operation of lower levels; such
effects therefore become available as exaptations conferring emergent
fitness a primary source of the different strength that species
achieve as effective Darwinian individuals in evolution.