Re: Hominid fossils FAQ file

Brian D Harper (bharper@magnus.acs.ohio-state.edu)
2 Jan 1995 04:03:17 GMT

In article <3e7dk7$snr@nntp1.u.washington.edu>,
Kathleen Hunt <jespah@u.washington.edu> wrote:
>>In article <3e1nv9$ouc@newsbf02.news.aol.com>,
>>Steve ThM <stevethm@aol.com> wrote:
>>>
>>>Granted, there are transitional forms within certain species. But can you
>>>list one clear-cut, completely authenticated transitional form between one
>>>species and another species? I do not believe you can. If so, please
>>>file the name of it to me for study.
>
>I posted several such examples just LAST WEEK. Perhaps you didn't see
>them. So here they are again.
>
>I particularly recommend you find Gingerich's 1980 paper and look
^^^^^^^^^^^^^^^^^^^^^^
>carefully at the figure that shows *hundreds* of specimens from entire
>*populations* of fossils, slowly diverging in average morphology until
>there were two distinct populations, which slowly became two distinct
>species, which slowly became two distinct genera, etc. [....]

Awhile back, Jim Lippard sent me an article by Donald Prothero on
punctuated equilibrium. Below is an exerpt which discusses Gingerich's
papers. I would be interested in your comments.

The complete paper can be obtained by anon. ftp:

//rtd.com/pub/zines/skeptic/01.3.prothero-punc-eq

=========================================================================
When the punctuated equilibrium paper first came out, reactions
were mixed. Since 1972 there have been many traditional
paleontologists who denied its importance, and trotted out their
favorite example of gradual evolution. Many of these "classic"
examples were restudied in critical detail, and turned out to be
ambiguous, or actually demonstrated punctuated equilibria better
than gradualism.
There were a host of more trivial objections and misunderstandings,
which have been discussed by Gould and Eldredge (1977) and
Gould (1992). Most studies fell short because they focused on a
single lineage (neglecting faunal variation) from a single section
(neglecting geographic variation), often showing change in only one
characteristic (neglecting morphological variation), which had not
been analyzed by rigorous statistical methods. Other cases failed
because they were on the wrong time scale to be relevant to the
debate, or too poorly dated to know anything about change through time.
For example, one of the main proponents of gradualism, Philip
Gingerich (1976, 1980, 1987), showed just two or three examples of
supposed gradual evolution in early Eocene (about 50-55 million years
old) mammals from the Bighorn Basin of northwestern Wyoming. But a
detailed examination of the _entire mammal fauna_ (monographed by Bown,
1979, and Gingerich, 1989) shows that most of the rest of the species
do not change gradually through time. Also, studies on specific
lineages in restricted areas cannot account for the possibility that
a gradual transition may actually reflect the migration of a clinally
varying population across a region through time. This was documented
by Schankler (1981), who showed that some of Gingerich's patterns
from the northern Bighorn Basin did not even hold up in the southern
Bighorn Basin, just a few dozen miles away!
-- Donald R. Prothero, "Punctuated Equilibrium at Twenty:
a Paleontological Perspective", _Skeptic_ vol. 1, no. 3,
Fall 1992, pp. 38-47.

[...]

>
>Kathleen Hunt
>--

-- 

Brian Harper                 bharper@magnus.acs.ohio-state.edu

Applied Mechanics     |

Ohio State University |   "It is not certain that all is uncertain,

Columbus, OH 43210    |    to the glory of skepticism" -- Pascal