Discontinuities in the Fossil Record

DAVID PLAISTED

Some evidences of discontinuities in the fossil record:

No wonder paleontologists shied away from evolution for so long. It never seemed to happen. Assiduous collecting up cliff faces yields zigzags, minor oscillations, and the very occasional slight accumulation of change--over millions of years, at a rate too slow to account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the fossils did not evolve elsewhere! Evolution cannot forever be going on somewhere else. Yet that's how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution.

Eldredge, N., 1995
Reinventing Darwin
Wiley, New York, p. 95


Most families, orders, classes, and phyla appear rather suddenly in the fossil record, often without anatomically intermediate forms smoothly interlinking evolutionarily derived descendant taxa with their presumed ancestors.

Eldredge, N., 1989
Macro-Evolutionary Dynamics: Species, Niches, and Adaptive Peaks
McGraw-Hill Publishing Company, New York, p. 22


The history of most fossil species include two features particularly inconsistent with gradualism:

1) Stasis - most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change is usually limited and directionless;

2) Sudden appearance - in any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and 'fully formed'.

Gould, S.J. (1977)
"Evolution's Erratic Pace"
Natural History, vol. 86, May


[T]he absence of fossil evidence for intermediate stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution.

Gould, S.J., 1982
"Is a new and general theory of evolution emerging?"
Evolution Now: A Century After Darwin
Maynard Smith, J. (editor)
W. H. Freeman and Co. in association with Nature, p. 140


W]e have so many gaps in the evolutionary history of life, gaps in such key areas as the origin of the multicellular organisms, the origin of the vertebrates, not to mention the origins of most invertebrate groups.

McGowan, C., 1984
In the Beginning... A Scientist Shows Why the Creationists are Wrong
Prometheus Books, p. 95


[G]aps between higher taxonomic levels are general and large.

Raff, R. A. and Kaufman, T. C., 1991
Embryos, Genes, and Evolution: The Developmental-Genetic Basis of Evolutionary Change
Indiana University Press, p. 35


L]arge evolutionary innovations are not well understood. None has ever been observed, and we have no idea whether any may be in progress. There is no good fossil record of any.

Wesson, R., 1991
Beyond Natural Selection
MIT Press, Cambridge, MA, p. 206

 

RUFUSATTICUS

Don't forget this quote from Gould:

"since we proposed punctuated equilibrium to explain trends, it is
infuriating to be quoted again and again by creationists - whether through
design or ******ity, I do not know - as admitting that the fossil record
includes no transitional forms. Transitional forms are generally lacking at
the species level but are abundant between larger groups." Gould, S.J.
(1983) p 260, Hens teeth and Horses toes. Norton & Co., New York

-RvFvS

 

THINKPLEASE

I'm fairly disappointed in David Plaisted's use of "scientists
quotes" to try to prove a point. It smacks of the quote mining efforts of
Henry Morris and Duane Gish, where they search through the scientific
liturature to try to use scientists words to say something else than what
they mean.

I'd like to point out the following quote, which should make at
least S.J. Gould's words much clearer...:


"since we proposed punctuated equilibrium to explain trends, it is
infuriating to be quoted again and again by creationists - whether through
design or ******ity, I do not know - as admitting that the fossil record
includes no transitional forms. Transitional forms are generally lacking
at the species level but are abundant between larger groups."Gould, S.J.
(1983) p 260., Hens teeth and Horses toes. Norton & Co., New York


And I agree with Gould, it is infuriating. For example, if I do a
search on the web for the first quote in Davids list by Dr. Eldredge, I
find 23 references to this quote by various creationist screeds. For older
quotes it is much worse, a single quote can be propogated to nearly 100
sites!

The problem is that David is trying to place statements by Gould and
Eldredge against gradualism as being against all of evolution, and that
simply isn't true. They espouse Punctuated Equlilibrium, which says that
most species stay in near stasis until they are forced to move into a new
ecological niche, in which case they either evolve or become extinct. If
you look at their statements in that light, their true meaning becomes
apparent.

 

JOE MEERT

I am surprised to see quote mining as the preferred method of arguing
about the fossil record. Others have pointed out Gould's response to
this quote mining, but Eldredge has also responded:

Earlier I said that creationists are poor scholars at best and at worst
have been known to distort the words and works of scientists.
Throughout the creationist literature, one sees repeatedly statements
such as this from Gary Parker

"Famous paleontologists at Harvard, the American Museum, and
even the British Museum say we have not a single example of evolutionary
transition at all"

Eldredge goes on to say:

"This statement is untrue." And discusses a couple of the more famous
examples of how he was deliberately misrepresented by creationists.

From Eldredge "The triumph of evolution and the failure of creationism".

 

DAVID PLAISTED

The problem is not with the use of quotations but when they are
misinterpreted. If we don't quote explicitly or implicitly then we are
just giving our own opinion.
I am looking for a smooth transition that will show the development of
anything new -- legs, wings, feathers, eyes, antennae, a new body form,
or whatever. One discussion group pointed me to this site for a
supposed transition between fins and legs:

http://www.glenn.morton.btinternet.co.uk/transit.htm

Unfortunately the fin-legs are often absent and when they are present,
not easy to see (especially the internal bone structure if any). The
following organism is supposed to have characteristics of both fish
and amphibians (this organism exists today):

http://www.naturia.per.sg/buloh/verts/mudskipper.htm

However a careful reading shows that the fins are really fins and the
lungs are not lungs. There are many alleged transitional sequences but
when you want to see a continuous change from anything to anything
substantially different (like fin to leg) suddenly the sequence becomes
much less continuous and the structures much less clear. Fins are
quite different from legs and it would take many many intermediate
forms to go from one to another. Likewise for wings, feathers, etc.
Another example is the evolution of sex (discussed on a different
thread). It seems most puzzling from an evolutionary point of view
why we should not have any good example of a substantial transition,
by a fairly continuous sequence of fossils; at least I have not seen
any. And it would take some really magical large-scale mutations to
accomplish the job!

David Plaisted

 

THE BARBARIAN

David Plaisted:
I am looking for a smooth transition that will show the development of
anything new -- legs, wings, feathers, eyes, antennae, a new body form,
or whatever. One discussion group pointed me to this site for a
supposed transition between fins and legs:

http://www.glenn.morton.btinternet.co.uk/transit.htm

The site, as you saw, shows a number of organisms that are intermediate
between fish and amphibians. Yes, they had lungs, but many of them also had
internal gills. Some had usable feet, but they couldn't get out of the
water, because the limbs were not attached well enough to permit supporting
the body on land. Long before these intermediates, we see, lobed-fin fishes
with bones in their fins that are the same as the long bones in our limbs.

An animal with legs and feet, internal gills, lungs, a lateral line system,
and the tail fin of a fish can be nothing but an intermediate.

Unfortunately the fin-legs are often absent and when they are present,
not easy to see (especially the internal bone structure if any).

There's quite a collection of these, and yes, there is a progression from
simple, stubby femur, tibia and fibula in the fins, to the rather well
developed legs and feet of Acanthostega. As you can see, the transitions
are so finely graded that sometimes they make a mistake until they get the
whole body to see what it most resembles.

That happens with the reptile/mammal transition, too. David, what would you
think a transitional between fish and amphibians would be like?

We can cross off the mudskipper as a transitional to vertebrates. Let's not
get sidetracked with something that looks sort of amphibian-like, but
doesn't have the basic amphibian anatomy.

 

DAVID PLAISTED

I am looking at the transitional fossils between fish and amphibians
found at http://www.glenn.morton.btinternet.co.uk/transit.htm.
First, Panderichthys already has an extensive bone system in its
"fins" so we know nothing (at least from this web page) where these
bones came from.

Then "Fish similar to Sauripterus" -- has 8 fingers inside its fins but
apparently no bones?

Then Livonia multidentata which has four stubby fins and could walk
on land, supposedly. Did it have bones in the fins?

Then Elginerpeton which had "primitive" limb bones but had already
a tibia and an ilia.

Then Obruchevichthys which has only a partial mandible.

Then Hynerpeton that has more advanced legs, bones, and pelvic girdle
than Ichthyostega (to be mentioned).

Then Densignathus rowei which is only known from a jaw.

Then Ichthyostega, the first animal with feet.

In all there are eight organisms, two only known from a mandible or
jaw, leaving six others. Even the first one already has an extensive
bone system in the fin-legs. For some others it was not mentioned
whether they had bones. One had 8 fingers inside fins, for the rest
feet or fingers are not mentioned except for the last that has feet.

So how did these leg bones develop? How did they attach to the
backbone? How did the feet develop? Quite a number of these
transitional forms look to be very closely related and it is not clear
that they evolved into anything significantly different, at least as
far as the legs and fins go.

All in all, this does not seem to be a continuous transitional sequence and
leaves a lot of questions about how leg bones and feet could evolve in
a fish.

Dave Plaisted

 

BARBARIAN

David,
Perhaps you should find a copy of "The Evolution of Vertebrate Design" by
Leonard Radinsky. (U. Of Chicago Press, I forget the date published)
In it, Radinsky carefully diagrams the structures of various lobed fin
fishes, and the modifications of them that led to the amphibians. You can
see from his work that the earliest crossopterygian fish had femurs and
tibia and fibula, long before they became functional walking legs. He can
also shows in simpilified diagrams how the neural crest and centrum elements
of the early bony fish spine evolved zygopophyses and became stronger and
eventually able to support the body out of water.

http://fig.cox.miami.edu/Faculty/Tom/bil160/20_verts2.html

I could probably run down more sources that aren't so nomenclature-dependent
for you. One great source would be "At the Water's Edge" (forget the
author, but a very good source for general information on how this happened)

Good hunting.