Natural Selection and Causal Productivity - Mechanism and Causality in Biology and Economics - page 145

favored or disfavored, as all the organisms would be of the same genotype
(Millstein 2006 ). However, Glennan claims, we cannot strictly say that increased
frequency of a form within a population produces decreased fitness of that form,
because production is a relation involving objects and events, while the population
is not (in this case at least) an individual object and the increase of frequency or
decrease of fitness are not individual events:
The only entities here are the fish and the bugs, the only activities are the activities of
individual fish and bugs, and the only interactions are when the fish eat the bugs and when
the bugs make baby bugs. (Glennan 2009 , p. 331)
It is only at the level of the activities and interactions of individual bugs, he
argues, that we find the mechanisms that produce new bugs.
Glennan's crucial claim here is that populations are not objects (or in MDC's
terms, entities) in this example. Glennan gives three reasons for thinking that
populations are not objects: (1) entities need to be localized in space and time;
they need to engage in particular activities at particular times and places. But, he
asserts, the population in the water bug case does not have these properties; the
population as a whole is spread out and does not engage in collective activities. The
only activities are those of the individual organisms - swimming, evading
predators, eating, etc. - and these are not activities of the population as a whole.
(2) What makes a collection of parts into a single entity is that these parts have a
stable structure, that the stable structure engages in activities as a unified entity, and
that these collected parts share a common fate. But, Glennan claims, when a fish
kills a water bug, it kills the whole water bug - it cannot kill its legs but not its body.
On the other hand, when a fish kills a water bug, it does not kill the whole
population of water bugs. The life of one water bug is more or less independent
of another. (3) One cannot say categorically that populations either are or are not
individual entities; the question of whether they are individuals only makes sense in
the context of analyzing a particular causal process. He allows that an ant colony or
a baboon troop may be an individual, but in this case the bugs in the pond are not.
Furthermore, according to Glennan, population-level properties do not produce
change because the population is not a part of the mechanism that produces changes
in genotype and phenotype frequencies. On Glennan's account of mechanisms, the
parts of the mechanism have to interact with other parts in order to produce the
behavior of the whole. But, he asserts, the population as a whole does not interact
with other entities as a whole in order to change its genotype and phenotype
frequencies.
4 Responses to Glennan's Arguments
It is this last presupposition of Glennan's - that causal production is mechanistic
production involving parts and wholes - that I will question first. I will then argue
that populations do exhibit the characteristics that Glennan says are necessary to be