IMPACT No. 84 June 1980
by Kenneth B. Cumming
Institute for Creation Research


Jay Williams1 tells about an old woman who was living out the last
days of her life. Surrounded by white walls, upon a white bed, in
care of doctors and nurses, this dark-skinned relict fought off
death with all her primitive vitality. She rebuked her attendants
and intermittently broke forth in song and chants. But inevitably
she collapsed onto her pillows and whispered, "Bury me behind the
mountains." And so she died, but her skeleton was placed instead in
a city museum, for she was the last of her kin. With her passing,
the Tasmanian people became extinct.

Extinction is like that. It is the absolute terminus for a formerly
recognized group of organisms. When mortality exceeds natality for a
sufficient time to bring the total number of individuals of a
species to zero or one (for those organisms which reproduce
sexually), then extinction is pronounced.2

Since life began, many organisms have been lost from the biosphere
through extinction. Some people feel that this is a normal
expectation of lifea parade of passing species. It is to be
expected that new "species" and higher taxa (levels of
classification) will progressively evolve to displace existing or
waning groups. On the other hand, some feel that this happening
represents a net loss to the total biota. This latter group says no
new "kinds" are being formed. Consequently, when populations of
unique organisms die out, that genome is gone forever.

If extinction is part of the natural order, why save endangered
species? The money and effort put into protecting, restoring, and
sustaining a few minor species of plants and animals becomes a
questionable national effort. Indeed, if we are a part of the
evolving cosmos, we should look forward to the new order and help
the evolutionary process! When we stop the parade, we slow down
evolution (i.e., we are keeping critical niches occupied too long).
The evolutionist requires extinction; it is like throwing out the
slum dwellers for urban renewal.

Congress addressed these issues, and in their wisdom they concluded
that endangered and threatened species of fish, wildlife and plants
"are of aesthetic, ecological, educational, historical, and
scientific value to the nation and its people."3 Perhaps protecting
organisms is good stewardship of finite resources. Whatever one's
view of the matter, the observation remains true that many more
species are being lost in our time than are being formed, and this
pace appears to be accelerating.

Extinction can occur as a result of any of three principal
pressures: mortality/natality imbalance, loss of critical habitat,
and minimum population density. Three examples are cited: Dodos in
historical times were found only on a few small islands in the
Indian Ocean. When man wiped them out of their tiny refuges, no
replacements were available to rekindle the speciesmortality
exceeded natality. A pair of ivory-billed woodpeckers is said to
require a territory of 5 km2 of primeval bottomland forest. A viable
population probably needed 160 km2. Much of this type of appropriate
habitat has gone and, to our knowledge, so has the bird. Theoretical
limits appear to exist for some species in that when the numbers
dwindle below that limit, genetic variability is lost to such an
extent that ultimate extinction is assured. There is a failure to
mate for social reasons below a certain population density. The
whooping crane and California condor may have passed below this
levelcertainly the passenger pigeon did.

The record of extinctions in the United States is startling. Since
the arrival of the settlers in America in the early 1600s, over 500
species and subspecies of native biota have passed on. Another 170
animals are designated "endangered" today. The rate of loss roughly
follows the national population increase.

Paleontologically speaking, there are two chief classes of
extinctions: those for which the paleontologist has a satisfactory
explanation, and those for which he has none.4 There are extinctions
in historical times which are due to depredations of man or stronger
animals upon weaker ones. Before those times in the distant past
there were even greater exterminations which apparently affected
organisms globally but do not have obvious causes. In the geological
record these are associated with the late Cambrian, Ordovician,
Devonian, Permian and Cretaceous strata. Since these latter events
were worldwide, they must have had worldwide causes. Two
explanations can be offered: either catastrophes or subtle and
insidious global reactions.

Newell5 says that man was the exterminator in historical times. A
few species of large mammals dropped out of the fossil record in
North America at the height of the last glaciation, and some of
these (perhaps the giant sloth and saber-toothed cat in California)
may have been due to over-hunting by man. The rate of extinction
picked up rapidly when the climate became milder and glaciers began
shrinking. Many large herbivores and carnivores existed worldwide
through a great range in climate, yet they died out in only a few
hundred years. In recent times about 75 percent of the North
American herbivores have disappeared, and most of the ecological
niches have not yet been filled. Glaciation was apparently not
important for these extinctions.

Some investigators have suggested that the large mammals may have
been hunted out of existence by pre-historic man using fire as a
weapon. The wipe-out coincided with rapid growth in agriculture.
Correlating extinctions to ancient earth's history has been a
scientific mystery according to Baker and Allen.6 The fossil record
contains mass extinctions in many layers. As an example of mass
extinction, two-thirds of the trilobite families disappeared at the
end of the Cambrian Period. Nearly one-half of the then known animal
species became extinct at the close of the Permian Period! A large
extinction of reptiles also occurred at the end of the Triassic. The
dinosaur extinction is the best known of all disappearances, and it
occurred at the close of the Cretaceous Period in a relatively short
period of time.

Many postulates have been put forward to account for mass
extinctions of organisms. One such postulate is that a nearby
supernova might have showered the earth with bursts of high-energy
radiation. Since water is a good shield against radiation, we would
expect to find the land organisms to be more affected than the
marine ones. Yet, we know that for certain periods most of the
extinctions occurred in the sea. Postulates on the change in the
earth's magnetic field suffer the same limitations.

Another postulate is that a "biological drive" became exhausted.
There is no direct evidence for any such force in nature or that
extinction is a result of its exhaustion.

Mountain building has been suggested as a cause. Attempts to relate
mountain building periods to times of mass extinction have led to
conflicting conclusions. Further, the greatest periods of mass
extinction are said to have occurred during geologically quiet times.

Climate change is the most popular explanation for the observed
extinctions. It was assumed that sudden changes in climate would
quickly eliminate vast numbers of organisms that could not adapt.
Perhaps the dinosaurs were not able to handle cold-prevailing
climates. But fossil plants do not show such changes to have
occurred at the time this hypothesis would predict them.
Fluctuations in the sea level have been well documented. It is known
that an increase or decrease of only a few feet would cover or
expose large areas of land. The correlation is that diversification
is greatest during times of flooding and extinctions greatly
increased during withdrawals. However, the worldwide effect would
imply massive continental coverage rather than coastal swamping.
Many hypotheses have been offered but none seem to hold a majority
opinion. What do the data show over geologic time? Valentine7 has
studied the states of the marine biosphere over time by examining
the fossil record for various benthic taxa. He has minimized the
bias of incomplete fossil records by using only well-skeletonized
taxa. Further, the benthic shelf environment was selected because it
is the best-represented major environment in the fossil record, and
also the environment most resistant to major forces of change.
Diversity levels of taxa including estimated diversity levels of
species of well-skeletonized marine shelf invertebrates during the
Phanerozoic, plotted by epoch. (After Valentine, 1973)

Notice that the greatest numbers of classes and orders occurred
early in the geological record with phyla remaining essentially the
same throughout. Families had a similar curve up to the Triassic
strata, but the number has increased with time to the present as
have the number of species. The curves show evidence of mass
extinctions that speak of worldwide catastrophes especially
associated with the Triassic. Valentine says, "in summary, the most
likely causes of mass extinction appear to be those factors which
are natural regulators of diversity under normal circumstances and
which have effects that pervade the entire planet." His catastrophe
is related to tectonic processes.

The creationist views these data as evidence supporting an early
highly diverse set of higher taxa which are declining in numbers
with time. Definite data in the geological record point to a
worldwide catastrophe especially in the Triassic and Jurassic
strata. Subsequent diversification of benthic families, genera, and
species since then is probably due to horizontal variation within
kinds.

When comparing the two models of extinctions, one would make
predictions something like the following:

COMPARISION ITEMCREATIONEVOLUTION

Initial Number of Taxa
Number of Taxa With Time
Higher Taxa (phyla, class order)
Lower Taxa (family, genus, species)
Geological Events
Niche Replacement With "New" TaxaLarge

Decreasing
Variable
Catastrophes
LimitedFew

Increasing
Variable
Uniformity
Extensive

Our present experience supports a rapid extinction of taxonomic
groups with very few documented "new" species appearances. This may
be just a declining period in earth history for biota, but man's
impact on the biosphere appears to force us to project an extended
period of losses under the human population increase and
technological pressure. Many more organisms will probably join the
Tasmanians before new organisms take their placeif they ever do.

REFERENCES

1 Williams, Jay, Fall of the Sparrow, Oxford, England: Oxford
University Press, 1951, p. 158.
2 Opler, Paul, "The Parade of Passing Species: A Survey of
Extinction in the U.S.," The Science Teacher, V. 44, No. 1, 1977.
3 United States Congress, "The Endangered Species Act of 1973,"
Public Law 93-205, U.S. Government Printing Office, 1973.
4 Stokes, William, "Extinction and Replacement," Essentials of
Earth History, Englewood Cliffs, New Jersey: Prentice-Hall, Inc.,
1973, pp. 48-485.
5 Newell, Norman, "Crises in the History of Life," Scientific
American, V. 200, 1963, pp. 76- 94.
6 Baker, Jeffrey and Garland Allen, "The Evolution of Animals,"
The Study of Biology, Reading, Mass.: Addison-Wesley Publishing
Co., 1968, pp. 577-597.
7 Valentine, James, "The Biosphere Level," Evolutionary
Paleoecology of the Marine Biosphere, Englewood Cliffs, New
Jersey: Prentice-Hall, Inc., 1973, pp. 373-408.

The Author: Dr. Kenneth B. Cumming is Chairman of the Biology
Department at Christian Heritage College and Research Associate in
Bioscience for ICR. He has a Ph.D. in Biology from Harvard
University, as well as extensive research, teaching and
administrative experience with the federal government and in three
universities.