Re: [ontolog-forum] Event Ontology

Gary Berg-Cross wrote:

> We may think that science uses a form of nominalism as we formulate
> theories whose simplifications name concepts used in the theory that may
> be useful for the theory, but not reflect the deep reality.   An oft cited
> one is the use of species in Biology. Ernst Mayr argued against a simple
> "typological thinking," found in biology (even evolutionary biology).
> Belief in the reality of "species" as a general form is a type of
> Platonic idealism, but in practice its use in  theory seems to be just a
> nominalist use.

The history about Mayr is a bit more complicated. Below you can find two
pages from the book I. Johansson (me) and N. Lynoe,  "Medicine &
Philosophy. A Twenty-Frist Century Introduction" (ontos 2008, pp. 418-20)
---------

How then to characterize what is common to all species, or at least to
sexual species? /---/
Evolutionary biology has made another kind of move; it has dropped the
pure class concept of species (Ghiselin 1997). A common modern definition
of sexual species, propounded by the German ornithologist and philosopher
of biology Ernst Mayr (1904-2005), says:

• Biological species are groups of actually or potentially interbreeding
natural populations, which are reproductively isolated from other such
groups.

The philosophical change involved in the move from the *typological*
species concept to the *biological* species concept is indicated by the
term ‘population’. According to the typological concept, a species is a
class, and a class has no boundaries in space and/or time. But a
population has such boundaries, and more than that. A population is not
just a class plus a conventional spatial and/or temporal boundary; the
individuals in the population should also be linked by chains of
interaction, which makes the population into a kind of spatiotemporal
particular. In a sense, the individuals of a population are to the
population what the cells of an organism are to the organism. A population
is, just like an organism, not a repeatable and class but a particular and
a property-bearer. The individual plants or animals of a biological
species are not *members* but *parts* of their species. In-between the
individuals and the whole population, biologists sometimes discern other
kinds of parts, e.g., local populations or ‘demes’.
A thought experiment may highlight the essence of the biological species
concept. If, on another planet (P) somewhere in the Universe, there are
lion-like animals that in principle can produce fertile offspring together
with Earth-lions, these P-lions are nonetheless parts of another
population. Therefore, according to the definition of biological species,
Earth-lions and P-lions have to be regarded as two different biological
species. Mayr is quite explicit on this (1988, p. 343). And a similar
remark holds for the temporal dimension. If, on Earth, lions become
extinct someday, but are then produced a second time by natural selection,
then these second-time lions would be a different population and,
therefore, also a distinct biological species. The expression
‘reproductively isolated’ is given such a broad sense in Mayr’s definition
that not only fertilization barriers (no zygote can be formed), hybrid
barriers (the zygote is not viable), and hybrid sterility count as
examples of reproductive isolation, but so also do behavioral differences
(the courtship rituals do not fit those of their mating partner) and
significant physical barriers (oceans, galaxies, etc.).
Typological species (species-as-classes-and-repeatables) are by definition
unchangeable, whereas biological species
(species-as-populations-and-particulars) allow change, since they are
property-bearers, too. Biological species can move on Earth, they can
exchange one niche for another, and they can even radically change their
genetic material. Does this new species concept therefore make the old
typological concept obsolete in the way modern chemistry has made obsolete
the concept of phlogiston? In other words: does the old typological
species concept refer to something merely fictional? The answer is
straightforwardly ‘no, it does not’. For the notion of ‘potential
reproduction’, which is at the heart of the typological species concept,
is still as applicable to individuals of different sexes as it ever was,
and it is even used in Mayr’s definition. In all probability, the
typological species concept will always be useful in some restricted
contexts. It might even be very useful within central biology. If it is
true that speciation only occurs during some relatively brief periods of
time (the theory of punctuated equilibria), the typological species
concept is as applicable in the normal equilibrium periods as it was in
pre-Darwinian theorizing.
On the other hand, it is not only evolutionary biology with its theory of
vertical gene transfer that has made it hard to apply the typological
species concept everywhere. Some organisms with prokaryote cells (e.g.,
bacteria) and some unicellular eukaryotes show evidence of horizontal gene
transfer, i.e., some organisms seem to receive genetic material not only
from their ancestors. When an organism produces an offspring and there is
a non-negligible horizontal gene transfer, then the organism cannot be
said to reproduce itself. Genetic engineering is a form of artificial
horizontal gene transfer.
 (The move from species-as-repeatables to species-as-particulars is
retained in phylogenetic systematics, the discipline that devotes itself
exclusively to finding genealogical trees that mirror the process of
speciation on Earth.)
---------------------

Best,
Ingvar

-- 
home page: http://hem.passagen.se/ijohansson/index.html

Received on Monday, 7 September 2009 11:28:56 UTC