1. Two kinds of evolutionary
thinking
Darwinism and Lamarckism
2. John Wilkins
May 22, 2013
Some quotes
“Evolution is so simple, almost anyone
can misunderstand it” – David Hull
“Natural Selection is not Evolution ” –
Ronald A Fisher
“Nothing in biology makes sense
except in the light of evolution” –
Theodosius Dobzhansky
3. John Wilkins
May 22, 2013
Star Trek Evolution
Why is it so
popular?
Where does
this idea come
from?
What should
we think about
evolution?
4. John Wilkins
May 22, 2013
The popular version
Grades
Direction
Perfection
Steady
Humans are the goal
5. John Wilkins
May 22, 2013
The scientific version
Branches
Randomness + selection
Irregular
No direction but locally
Humans are one animal among
many
6. John Wilkins
May 22, 2013
Names
The popular version is called many things:
Great chain of being
Ladder of progress
Lamarckism
The scientific version is also called many
things:
Darwinism
Neo-Darwinism
The Modern Synthesis
7. John Wilkins
May 22, 2013
Progress
Depends on the “target”
Jacob’s Ladder - God at the top,
something ugly at the bottom
Evolution has always been thought
to be progressive
Until Darwin (and even then)
8. John Wilkins
May 22, 2013
There are two kinds of
evolution
The one Lamarck developed and
made known.
The one Charles Darwin developed
and made known
Only Darwin’s is truly novel, and yet
it is the least well known, and so it
takes the longest to really “get”.
9. John Wilkins
May 22, 2013
Before evolution
Western thinking was historical
because of Christian theology, but
change tended to a goal
Everything was ranked from lowest
to highest
Higher things were “more perfect”
than lower things
10. John Wilkins
May 22, 2013
The medieval view
Stones … mere being
Fire … + motion
Plants … + growth
Animals … + sense
Man … + reason
Heaven … + incorruptibility
Angels … + knowledge of good
God … with the lot + perfection
Raymond Lull, 1512
12. John Wilkins
May 22, 2013
Great chain of being
A view that goes back to the Greeks
Everything is lined up along a scale
Made into a time series in the 17th
and 18th centuries
Lamarck one of the first
evolutionists, and followed this
view
13. John Wilkins
May 22, 2013
Three “Lamarckisms”
That changes to individual
organisms are likely to be inherited
or will affect the hereditability of
traits.
That things evolve on a
preprogrammed pathway to
perfection
That change is predictive of the
needs (or wants) of organisms
14. John Wilkins
May 22, 2013
Lamarck’s scale from lower to
higher
At first a single scale
Later, two, one for invertebrates,
one for vertebrates
Each “species” underwent change
up the scale
16. John Wilkins
May 22, 2013
Spontaneous generation
Lamarck accepted the constant
generation of living things in their
simplest form, from the non-living
Each new spontaneous generation
started a lineage
Each lineage would evolve through the
same stages as the earlier ones had
Later, he allowed for some branching
18. John Wilkins
May 22, 2013
Bees and brains
“It is absurd to talk of one animal being
higher than another – We consider those
where the cerebral structures intellectual
faculties most developed, as highest. – A
bee doubtless would where the instincts
were.” Charles Darwin, Notebook B
“Never say ‘higher’ or ‘lower’” Darwin
What about the flowers? What would they
say?
19. John Wilkins
May 22, 2013
Darwin’s view
Things get better locally, not globally
Being “fitter” is a matter of being able to do
well then and there only
Populations, not whole species, evolve
Evolution branches all the time
Everything has evolved as much as
everything else!
23. John Wilkins
May 22, 2013
Darwin used the tree metaphor
This, too could be misused
Although Darwin’s tree was not
directional at first, others came to
be
24. John Wilkins
May 22, 2013
Haeckel’s
mighty
oaks
Central trunk leads
directly to humans,
and everything on
the trunk is
somehow
“important”
25. John Wilkins
May 22, 2013
Indirect
progressionism
Patten (1925) makes a
direct line through
arthropods (bugs) to
vertebrates (non-bugs)
26. John Wilkins
May 22, 2013
Indirect racism
Notice how the earlier (and
“less evolved”) forms are
shown at the left of the
diagram. Now notice the
“races” of Homo - in order,
African (i.e., the “Negro”),
Australian (aboriginal),
Mongolian (the “Asiatic”),
and of course the
European.
Diagram c1920. There was
no geological evidence at
the time (or now) of any of
this.
28. John Wilkins
May 22, 2013
Intelligence still
at the top of the
chain…
Despite the divergence of
evolution until now, Teilhard
(1955) still thinks that it will
all come together with humans
as the final players. At least he
isn’t racist about it – all
“socialised” humans will evolve
to the Omega Point.
31. John Wilkins
May 22, 2013
Any ancestors at all?
We cannot be sure that a fossil or
living species is actually an
ancestor
Might be a sibling of the ancestor
Might be the ancestor, but how to
tell?
At best, we have likelihoods
32. John Wilkins
May 22, 2013
Populations
All evolution happens to
populations
Not individuals (that’s “development”)
Not entire species (that’s
“speciation”)
Not larger groups (that’s artificial)
33. John Wilkins
May 22, 2013
Natural selection
Does not equal “evolution”
Is the process of adaptation (of
populations)
Is not all that happens in evolution
(that’s called “panadaptationism”)
34. John Wilkins
May 22, 2013
Selection
Follows the fitness
peaks (available ways to
make a living).
They have to be
reachable, and they
have to be better than
what is already in place.
Changes the frequency
of genes in populations.
35. John Wilkins
May 22, 2013
Lessons to be learned
Progress is not necessary
There is no “next step”
Selection is not all there is to
evolution
Everything is as evolved as
everything else
36. John Wilkins
May 22, 2013
Further reading
Bowler, Peter J. Evolution: The History of an Idea. Berkeley:
University of California Press, 1984.
Dennett, Daniel C. Darwin’s Dangerous Idea: Evolution and the
Meanings of Life. New York: Simon and Schuster, 1995.
Jordanova, L. J. Lamarck, Past Masters. Oxford; New York:
Oxford University Press, 1984.
Lovejoy, Arthur O. The Great Chain Chain of Being: A Study of
the History of an Idea. Cambridge, Mass.: Harvard University
Press, 1964 (1936).
Editor's Notes
Lamarck proposed two “Laws”, which was the aim of every scientist of the time; to make laws that paralleled Newton’s great laws of physics. His first law was use strengthened of an organ and disuse weakened it. If an organism failed to make use of its parts, then those parts would disappear. His second law was that everything that nature caused to be acquired or lost by individuals because of the conditions they had been exposed to over a long time would be conveyed to new generations. In short, the species would “learn” from experience. This would be enough to cause organisms to evolve. But he also thought that they were impelled to become more perfect over time by a “subtle fluid” that had an innate tendency to drive this improvement by purely physical means. Many later thinkers believed, in part because of the mistranslation in to English of his words, probably by Lyell, that he thought that these changes could be brought about predictively – that a giraffe could “strive” to reach leaves at the top of a tree and so pass on a slightly longer neck to its progeny. This is wrong; but it remains a sense in which people think of things as Lamarckian.
Despite the objections already made to spontaneous generation of living things from non-living material, Lamarck thought that simple forms (not, for example, more advanced forms like flies or mice) were continually appearing. Over enough time, they became advanced forms. Each of these forms was a single lineage. Initially he didn’t think that they branched off to become different forms; in true Chain style he thought they all followed the same pathway but as he worked out his view of adaptation by use and disuse he realised that forms would change in different ways. By 1809 he was prepared to admit many different branches, but always an increase in organisation.
Peter Bowler gave this figure to explain Lamarck’s progressivism. The scale of organisation, or the graded chain, at any one moment is filled by organisms that have their own distinct history. Humans evolved, in his opinion, from older ape forms, but not from the present apes, nor did apes and humans share common ancestors. When we have evolved further, apes will evolve to fill the “human grade”.