Re: Common descent before Darwin?

Bobby D. Bryant wrote:
On Tue, 14 Mar 2006, John Wilkins <john@xxxxxxxxxxxxx> wrote:

Bobby D. Bryant wrote:

What was the status of the idea of common descent before Darwin
published? Was the idea current among scientists, and Darwin
just provided a mechanism? If so, how widespread was it?
That species were organised into tree diagrams, or logical
classifications that could be presented as tree diagrams, was widely
known. It was part of the inheritance of logic. For example, George
Bentham (nephew of the famous Jeremy) published a logic text in 1827
with tree digrams in it using biological examples, before he turned
himself to botany (and became a famous botanist, and a friend of
Darwin's).

Karl Ernst von Baer proposed a classification of sorts based on
developmental divergence which was published in Scotland as a tree
diagram by a commentator, and it has been argued that Darwin was
influenced by this.

Darwin's trees are slightly ambiguous. The logical tradition allowed
only for dichotomous trees, and while Darwin's diagram in the Origin
has many branches, if you step back a bit and look at the whle
thing, you'll see that the overall phylogeny is dichotomous.

However, I am not aware of anyone who proposed common descent as
Darwin did before him. Lamarck had a variable branching at about the
phylum level but nobody treated of speciation as the basis for
common descent or "groups under groups". A tradition known as
Quinarianism held that species were arrayed in quintuplets around
the edges of a circle and had affinities with species from other
groups in "osculating" (i.e., touching or kissing)
circles. Basically there was a lot of confusion before 1859.

IMO Darwin's greatest contribution, and the one that earned
acceptance of evolution, was common descent.

Thanks.

What did they make of the fossil record at that time?

The best source is Cuvier's "Eloge historique du Chevalier de Lamarck par
Cuvier", in which he admits that different fauna existed over time, but denies
that the sort of progressive sequence Lamarck required could be found.

--
John S. Wilkins, Postdoctoral Research Fellow, Biohumanities Project
University of Queensland - Blog: evolvethought.blogspot.com
Who are you going to believe? Me, or your own eyes?

.

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    (talk.origins)