Species
a 3 weeks block in „Great Ideas” of Science
George Kampis
Basler Chair, ETSU, Spring 2007
The concept of species
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Species: links to fundamental ideas in sci
What is a species? --> Species problem, SP.
(Is it important? well:
(1) taxonomy and everyday life(use),
(2) explanation
(3) philosophy: undertand "Nature", and the
"nature of things" - ontology)
History of the species concept
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categories,
fixism,
population,
anti-essentialism,
problems (language etc)
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Categories
• folk biology (1970 as anthropo, but 10,000 yrs
as user): B.Berlin, S.Atran, etc.
• Aristotle: types, categories, essences /accidents,
stability
• category theory (membership, kind as
explanation, cf folk biology)
• immutability (cf Plato's "ideas", A finds them in
nature: "joints of nature", P)
• natural kinds (eg elements, particles.... etc).
Fixism
• Bible, scholasticism, Linne. "evolution" as
exctinction/creation: Cuvier etc.
• Linnaeus recognized that variation was
possible within a species, but was not
always sure where one species left off and
another began.
• http://evolution-facts.org/Ev-V3/3evlch29a.htm
Populations, background
• revolution in 19c.:
• A. Smith: distance is time (geol. layers, but
also sometimes exposed/cut off)
• layers etc were known before but not
understood.
• Next: Lyell, father of g., principle:
"uniformitarian" p.
Populations, Lyell
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Lyell's "Presentism" or "Actualism"
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The subtitle of Lyell's Principles was "Being an Attempt to Explain the
Former Changes of the Earth's Surface, by Reference to Causes Now
in Operation." It is pretty clear that in restricting geological theories to
causes that we can observe acting in the present, Lyell wanted to rule
out catastrophes on methodological grounds. No catastrophes are
observed in the present. So, it is illegitimate to postulate them acting
in the past in order to explain the present state of things.
Lyell was appealing to a particularly strong version of the vera causa
principle. He was in close contact with Herschel during this period and
was well-acquainted with Herschel's views prior to the publication of
the Preliminary Discourse in 1830.
Many geologists (Sedgwick, Conybeare, Agassiz) rejected Lyell's
presentism.
http://branemrys.blogspot.com/2005/02/darwins-logic-preliminaries-veracausa.html
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Vera causa vs relevant explanation
• C.G. Hempel deductive nomological
theory
• The concept of general law, „covering law”
• More importantly, relevance
• Relevant = helps you believe/bring forth
• Combines causal efficacy, believability and
manipulability
Lyell, cont’d
• Lyell adds process. Sediments, etc,
• and forces: (waves, wind, rain etc)
• creationism: wonder about geology/graphy,
"how come".
• humble forces, 4 billion yrs of destruction
(and some buildup).
• difficult to believe until... but even then:
• The analogous problem of continental drift
(the creationism problem of geol).
Continental drift
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refers to the movement of the Earth's continents relative to each other.
Frank Bursley Taylor had proposed the concept in a Geological Society of America
meeting in 1908 and published his work in the GSA Bulletin in June 1910.[1] Abraham
Ortelius, Francis Bacon, Antonio Snider-Pellegrini, Benjamin Franklin, and others had
noted earlier that the shapes of continents on either side of the Atlantic Ocean (most
notably, Africa and South America) seem to fit together. The similarity of southern
continent fossil faunae and some geological formations had led a small number of
Southern hemisphere geologists to conjecture as early as 1900[citation needed] that
all the continents had once been joined into a supercontinent known as Pangaea.
Frank Bursley Taylor suggested that the continents were dragged towards the
equator by increased lunar gravity during the Cretaceous, thus forming the Himalaya
and Alps on the southern faces.
Alfred Wegener was the first to formally publish the hypothesis that the continents
had somehow "drifted" apart. However, he was unable to provide a convincing
explanation for the physical processes which might have caused this drift. His
suggestion that the continents had been pulled apart by the centrifugal pseudoforce
of the Earth's rotation was considered unrealistic by the scientific community.[2]
The hypothesis received support through the controversial years from South African
geologist Alexander Du Toit as well as from Arthur Holmes. The idea of continental
drift did not become widely accepted even as theory until the late 1950s.
Darwin and the Beagle
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On 27 September 1825 Beagle docked at Woolwich for repairs and fitted out for her
new duties at a total cost of £5,913. Her guns were reduced from ten cannons to six
and a mizzenmast was added to improve her manoeuvrability, thereby changing her
from a brig to a bark (or barque).
Beagle set sail on 22 May 1826 for her first voyage, under the command of Captain
Pringle Stokes. The mission was to accompany the larger ship HMS Adventure (380
tons) on a hydrographic survey of Patagonia and Tierra del Fuego, under the overall
command of the Australian Captain Philip Parker King.
Faced with the more difficult part of the survey in the desolate waters of Tierra del
Fuego, Captain Pringle Stokes fell into a deep depression. At Port Famine on the
Strait of Magellan he locked himself in his cabin for 14 days, then on 2 August 1828
shot himself and died in delirium 12 days later.[1] Captain Parker King then replaced
Stokes with the Executive Officer of the Beagle, Lieutenant W.G. Skyring. They sailed
to Rio de Janeiro where on 15 December 1828 Rear Admiral Sir Robert Otway,
commander in chief of the South American station aboard HMS Ganges, named as
(temporary) Captain of the Beagle his aide, Flag Lieutenant Robert FitzRoy.
The 23 year old aristocrat FitzRoy proved an able commander and meticulous
surveyor. In one incident a group of Fuegians stole a ship's boat, and FitzRoy took
their families on board as hostages. Eventually he held two men, a girl and a boy who
was given the name of Jemmy Button, and these four native Fuegians were taken
back with them when the Beagle returned to Plymouth, England on 14 October 1830.
Darwin and the Beagle 2.
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The second voyage of HMS Beagle from 27 December 1831 to 2 October
1836 was the second survey expedition of HMS Beagle, under captain
Robert FitzRoy who had taken over command of the ship on its first voyage
after her previous captain committed suicide. FitzRoy, fearing the same fate,
sought a gentleman companion for the voyage. The student clergyman
Charles Darwin took the opportunity, making his name as a naturalist and
becoming a renowned author with the publication of his journal which
became known as The Voyage of the Beagle.
The Beagle sailed across the Atlantic Ocean then carried out detailed
hydrographic surveys around the coasts of the southern part of South
America, returning via Tahiti and Australia having circumnavigated the
Earth. While the expedition was originally planned to last two years, it lasted
almost five.
Darwin spent most of this time exploring on land; three years and three
months on land, 18 months at sea. His work made his reputation as a
geologist and collector of fossils, and his detailed observations of plants and
animals
Darwin, Henslow, Lyell
• R. McCormick was the naturalist first..
• Darwin theologist (and almost a physician)
• Henslow: priest, D’s job-broker, a highly
intellectual man
• Gives Lyell’s Principles to D who takes it
with him
• Imagine the atmosphere of a trip like this.
The book is among the very few links D
has to „civilization” – or at least to home.
Species in 19c.
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"scala naturae", linear order, great chain of being (Charles Bonnet, Contemplation de la
nature, 1764)
Lovejoy, Arthur Oncken: The Great Chain of Being: A Study of the History of an Idea,
Cambridge, Mass.: Harvard University Press, 1936
Species in 19c. and their placement in ths structure of knowledge: understand the spirit of
time (and of contemporary investigation)
The age of discoveries (of Earth): British Crown. Colonization, surveys, raw materials, etc.
The birth of science as profession: naturalist w/ salary.
Positivism as an ideology: naturalism = observation, „unbiased observer”, e.g. colonel X.
The catalog of the world. Large collections, Protype based description, proliferation of
species.
Anectodically, species = specimen, specimen = species, e.g. male and female specimens
(today: variations, variants. Emerging debates: species, subspecies, „variant”)
cf variant kidney. So, even today: prototype = tpye, variation = different class, eg.
pathology
Darwin’s discovery
• Maybe the biggest discovery in science ever… (that no types,
no kinds exist). The discovery of evolution (which was long
suspected) is but a consequence.
• Variation is extended (is the rule) and (often) continuous
• Co-varies with distance and the accessibility of regions.
• Large parts of the Origin of Species devoted to this!
• „difficulties of classificiation”: sees type, mix, type, etc.
• Darwin: space IS time, and time can host a process (of
transformation – or, as D. calls it, „transmutation”)
• Made possible through abandoning the species concept.
• Each species is a mixture (natural polimorphism)
• Basis is individual (variant), unity is maintained by crossreproduction
• Debates about Darwin and Wallace… W is a lesser figure.
• Origin of Species is NOT about the origin of species…
Darwin’s MILD nominalism:
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Box: nominalism, realism.
http://en.wikipedia.org/wiki/Nominalism
Nominalism arose in reaction to the problem of universals. Specifically, accounting for
the fact that some things are of the same type. For example, Fluffy and Kitzler are
both cats, or, the fact that certain properties are repeatable, such as: the grass, the
shirt, and Kermit the Frog are green. One wants to know in virtue of what are Fluffy
and Kitzler both cats, and what makes the grass, the shirt, and Kermit green.
The realist answer is that all the green things are green in virtue of the existence of a
universal; a single abstract thing, in this case, that is a part of all the green things.
With respect to the colour of the grass, the shirt and Kermit, one of their parts is
identical. In this respect, the three parts are literally one. Greenness is repeatable
because there is one thing that manifests itself wherever there are green things.
Nominalism denies the existence of universals. The motivation to deny universals
flows from several concerns. The first one concerns where they exist. Plato famously
held that there is a realm of abstract forms or universals apart from the physical
world. Particular physical objects merely exemplify or instantiate the universal. But
this raises the question: Where is this universal realm? One possibility is that it is
outside of space and time. However, some assert that nothing is outside of space and
time. To complicate things, what is the nature of the instantiation or exemplification
relation?
Conceptualists hold a position intermediate between nominalism and realism, saying
that universals exist only within the mind and have no external or substantial reality.
Darwin: species is a convenient tool
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But reflects patters of (origin and) extinction as well.
Sampling and the fossile record add to this (connects and separates)
Relative concept: e.g. ring species
http://en.wikipedia.org/wiki/Ring_species
Mayr’s „biological species”
• A species is a set of interbreeding
individuals...
• Reproductively isolated from others
• (e.g. mechanically, behaviorally, in
terms of mating preference, etc.)
New Species
Neofelis diardi
Neofelis nebulosa
http://news.bbc.co.uk/1/hi/sci/tech/6452555.stm
….recent molecular genetic analyses (mtDNA, nuclear DNA sequences,
microsatellite variation, and cytogenetic differences) have revealed that there is a
strong case for reclassification and the defining of two distinct species of clouded
leopard - Neofelis nebulosa (mainland Asia) and Neofelis diardi (Indonesian
archipelago).
The Species Problem
• interbreeding, cf. above figure
• similarity: multidimensional (e.g. gull picture, first smaller,
then the color changes… etc)
• Species problem is an issue of the general problem of
identity (species as individuals, Hull and Ghiselin)
• e.g. personal identity (despite metabolism, and sleep,
maturation, etc: „we are the same” – what connects?)
• “the name” – rigid designator w/ continuity (somebody
else’s problem of how to identify)
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but can be be maintained across properties by
ostension).
• e.g. how ships are rebuilt, cf. Neurath’s ship
Family resemblance
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An influential idea in the philosophy of language, first proposed by Ludwig
Wittgenstein in his book Philosophical Investigations.
Wittgenstein discussed examples of terms which he argued would not admit
of a full and complete definition. How, he asks, would one go about giving a
definition of "game"? He argued that there is nothing that is common to all
games, but rather that games held certain similarities and relations with
each other. He admonished his reader not to think, but to look, at the vast
range of things that we call games. Some games involve winning and
losing, but not all; some are entertaining, but not all; some require skill or
luck, but not all. [1]
Similarly, he argued that there is nothing that all "numbers" have in common
Prior to Philosophical Investigations the ideal way to give the meaning of
something had been thought to be by specifying both genus and differentia.
So a 'triangle' is defined as 'a plane figure (genus) bounded by three straight
sides (differentia)'.
Logically, this sort of definition can be seen as a series of conjunctions; A
triangle is a plane figure and has three sides. More generally, "P" might be
defined using a simple conjunction of "A" and "B":
Family resemblance 2.
A disturbing thought: it can be anybody’s family.
Cf. the anecdote of MK’s friend the garbage collector
Along a series of such pictures (how long?), a road to everyone.
Really my family is…
Is there anybody here like me? Cf anecdote w/ Dora at church
How long: Six degrees?
More on these (will be/was) at the Basler lecture, March 14, Brown Hall….
Categorization, is it possible?
• Quite general q., e.g. planet
or not (“When I was your
age, Pluto was a planet”)
• Some properties are
shared, some not
Natural Kinds
• Aristotle, Quine: Problem of natural kinds
• Problem of induction (cf explanation: by virtue of being a cat, it mieuws,
and it MUST do so)
• Hempel again: do non-black non-ravens confirm „all ravens are black?”
• Projectible predicates
• http://en.wikipedia.org/wiki/Natural_kind
• Populational species definition: no natural kind, no projection possible
Natural kinds, cont’d
Quine: once you understood it, you dont need it
A test of 3 definitions
Fruchterman-Reingold (FR)
plot of a single species on
BSC.
Lines represent possible
reproduction events.
Circular FR plot of partitions of
CSC under T1 in the interval
T0=0 to T=644. The picture
shows one giant, connected
lineage, and several small,
isolated components (on the
left).
Clusters against time.
Convergence to (typically)
one PSC cluster. 60 runs, 10
for 6 random seeds each,
from dcluster = 0.9 to 1.4 .
Time goes left to right, the
clustering constant increases
right to left. Vertical axis
shows number of clusters.
• 1. The BSC. Although refined many times
since its introduction (cf. Chung, 2003),
the main feature (or grouping criterion) of
the BSC has remained unchanged: on the
BSC, a species corresponds to a maximal
group of potentially interbreeding
organisms (a „Mendelian” population) that
are reproductively isolated from other
organisms.
• 2. The CSC. On the Cladistic Species
Concept, a species is a (minimal) lineage
of populations delineated by two branching
events („points”) on the phylogenetic tree
(Mishler–Donoghue, 1982). The grouping
criterion in this family of concepts is the
ancestral-descendant relation
• 3. The PSC. On the phenetic concept, a
species is a cluster of similar organisms
delimited with the aid of some statistical
clustering method. The clustering is based
on a huge number of characters of
organisms.
Back to Darwin
So why is SP a problem?
• Taxonomy, science, conceptualization…
• Can they be simultaneously satisfied?
• Species as
– Individuals
– Lineages
– Clusters
– Homeostatic systems
– Sets, relations…
Resources
• http://plato.stanford.edu/entries/species/
• http://en.wikipedia.org/wiki/Species_Problem
• Etc