Re: transitional fossils

From: Dr. David Campbell <>
Date: Mon Dec 05 2005 - 15:34:25 EST

> Prediction: The fossil species should form an evolutionary tree.
> Falsification: The fossil record reveals a series of "big bangs"
> followed by a thinning of the ranks by extinctions. In each "big
> bang" new species appear, and then they remain unchanged until they
> reach extinction. If anything, it appears more like an inverted
> evolutionary tree. Rather than the prediction of a single trunk
> leading to many branches and twigs of diversity, what we actually
> find is the opposite: the rapid appearance of species followed by a
> narrowing as species reach extinction.

This falsification is false on several counts. The fossil record
includes several bangs, but also plenty of gradual diversifications.
Neither of these is inconsistent with an evolutionary tree pattern,
and in fact the fossils do fit well into an evolutionary tree. Even
within the "bangs", there are often transitional forms. Many species
show considerable variation or directional trends and are not
unchanged until extinction, if they actually go extinct as opposed to
evolving into something else.

Although individual branches often give out, overall there is
continued diversification over time, so that the Pleistocene fauna is
probably close to the historical maximum diversity (modern diversity
is impoverished due to human activity). However, younger deposits are
generally more widespread and better preserved, so there's a bias to
the data.

> Again, the "intermediates" which appear between the different
> species are "intermediates" only if evolution is true. It is not
> false that the species appear abruptly in the fossil record and then
> persist with little or no change. That is what we observe (even
> Dawkins admits to this). Sure, we observe minor changes, as we do in
> the field today. But such do not support macro evolution.

It is false to claim that all species appear abruptly in the fossil
record and then persist with little or no change. If we have good,
detailed information for a fairly continuous section of time, we see
some species that have little or no change, some species that vary a
bit, and some that show clear trends. Any of these may also have a
transition to a new species during the observed interval. This is
expected based on evolutionary theory. There's an old warning for do-
it-yourselfers: "If it ain't broke, don't fix it." The same applies
to evolution. If an organism is reasonably successful, most
significant mutations will probably be detrimental. The organism will
tend to stay the same, though this also depends on the degree of
competitive pressure. If the environment changes (climate shift, new
predator, etc.), more mutations significant may become advantageous.
If the competitive pressure is low, there's more room for mutations
without preventing survival and reproduction.

Things can be intermediate without evolution. A square is
intermediate in some ways between a triangle and a pentagon.
Archaeopteryx is intermediate between modern birds and reptiles, no
matter how you claim it came into existence. However, the existence
of numerous intermediate forms throughout the fossil record strongly
argues for evolution as a good explanation. Tracing through time, we
see major changes, not just minor ones. For example, there is a nice
evolutionary series going from a cap-shaped shell through a laterally
compressed cap-shaped shell to bivalves and another series from cap-
shaped shell to tall cap-shaped shell to serially partitioned cap-
shaped shell to cephalopods. These show the evolution of two

What is macro evolution? The term macroevolution is used without
consistent definition by those who say they reject it. We do observe
new species forming today in lab and in the wild, contrary to claims
of some ID and YEC advocates who claim that each species was created
separately. Higher taxa (genera, families, orders, classes, phyla,
etc.) are a bit more difficult to identify, since the criteria for
deciding what qualifies as one of those are somewhat arbitrary and
ultimately reflect their existence as an apparently distinct group.
For example, number and configuration of wings is an important factor
in distinguishing orders of insects. Flies have just two wings, but
we can make a mutant fruit fly with four wings. Based on the usual
criteria for identifying orders of insects, it constitutes a new
order, but we just think of it as a mutant fruit fly. However, if we
release a bunch of these mutant fruit flies onto a newly formed island
or other place with some vacant niches and give them a few million
years or so, they might diversify into a distinctive group. Since
they are descended from true flies, there would be a bit of a problem
in deciding how to classify this group, but one could argue that
morphologically they deserve recognition as a new order. Thus, we
need millions and millions of years of hindsight to determine whether
we are observing new orders, etc. being formed today. We can see some
examples of things requiring new genera when reproducing hybrids are
created by crossing things in different genera. The hybrid doesn't
really belong in either parent genus.

Dr. David Campbell
425 Scientific Collections Building
Department of Biological Sciences
Biodiversity and Systematics
University of Alabama, Box 870345
Tuscaloosa AL 35487-0345  USA
Received on Mon Dec 5 15:38:41 2005

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