Out of Order: Function and Malfunction in the Biological and Biomedical Sciences
Biol Theory
Out of Order: Function and Malfunction in the Biological and Biomedical Sciences
Isabella Sarto-Jackson 0
0 Konrad Lorenz Institute for Evolution and Cognition Research , Klosterneuburg , Austria
Now take a human body. Why wouldn't you like to see a human body with a curling tail with a crest of ostrich feathers at the end? And with ears shaped like acanthus leaves? It would be ornamental, you know, instead of the stark, bare ugliness we have now. Well, why don't you like the idea? Because it would be useless and pointless. Because the beauty of the human body is that it hasn't a single muscle which doesn't serve its purpose; that there's not a line wasted; that every detail of it fits one idea, the idea of a man and the life of a man.
-
Ayn Rand’s main protagonist in The Fountainhead, the
obstinate architect Howard Roark, compares his view of an
architectural masterpiece to the impeccable organization of
the human body. According to Roark, every inch of the
human body serves a purpose, a conviction he applies just as
much to organisms as to his buildings.1 This belief in an
optimized organismal organization of the human body (and
by extrapolation of living beings in general) has not only
been a prevailing subject in literature for a long time, but has
also reached broad significance in the natural sciences. For
centuries, the consensus view of the human body in the
biological and biomedical sciences was epitomized in the
notion of the perfect machine
(Ochsner 2010)
.2 We owe the
machine analogy to Descartes
(Lewontin 1996)
, whose
idea about the organism as a machine has exerted its
influence for more than three centuries. The view of organismal
optimization, on the other hand, was imported with the
adaptationist program towards the end of the 19th century.
The latter bestowed natural selection with a near
omnipotence ‘‘in forging organic design and fashioning the best
among possible worlds’’
(Gould and Lewontin 1979,
p. 584)
. These models have served their purpose well and led
to important theoretical insights, biotechnological progress,
and remarkable biomedical advancements. On the other
hand, the perfect machine metaphor is uplifting from a purely
psychological point of view, because it conveys a picture of
an elaborate, fine-tuned system whose parts ensure a
sophisticated and immaculate functioning as a whole due to
the specificity and selectivity of the parts. This is reassuring,
because it gives the impression of having—in principle—
control about the comprising units as well as their
interrelations, interactions, and underlying mechanisms. Yet, at the
same time, the perfect machine model has left scholars
grappling with the aftermath of its integral assumptions
when dealing with system failure of such allegedly
optimized and idealized systems.
To investigate malfunction in complex systems, one
must agree first on what the system’s natural functioning
is. For centuries, biologists, physiologists, and medical
practitioners have applied the notion of function to almost
every type of structure and process that describe
biological phenomena, and they implicitly fell back upon the
perfect machine metaphor. Since the 1950s, the concept
of function, as used by pundits of those disciplines, has
1 Roark clearly does not consider spandrels (or rather pendentives,
for that matter
(Gould 1997)
) as architectural assets.
2 ‘‘When we arrive on this earth we are endowed with the most
perfect, the most efficient, and the best constructed machine ever
devised—our body. A machine beautifully engineered and
constructed with the best materials with no planned obsolescence’’
(Ochsner 2010, p. 44)
.
come under philosophical scrutiny. Debates about
functional ascriptions and functional explanation in the
biological and biomedical sciences culminated in the early
1970s when Larry Wright published his work on the
etiological account, and Robert Cummins published his
work on the causal-role account. Wright’s analyses were
rooted in a realist concept of function and claimed that
‘‘[t]he function of X is Z means (a) X is there because it
does Z ; (b) Z is a consequence (or result) of X’s being
there’’
(Wright 1973, p. 161)
. According to Wright, such
a definition of function satisfied three requirements: (1) it
offered a criterion for distinguishing a function from a
mere effect; (2) it applied both to biology and to artifacts;
(3) it was able to capture the normativity of functional
ascriptions, that is, the implicit assumptions that
malfunction is always a possibility (a given object may have a
function, and nevertheless be unable to accomplish that
function). Against this claim, Cummins formulated a
causal-role concept of functions that defines functions as
crucially embedded in a system, thereby giving it its
explanatory power. According to the causal-role account,
ascribing function to a system is ‘‘to ascribe a capacity to
it which is singled out by its role in an analysis of some
capacity (...truncated)