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Living Fossils: How Significant Are They?

Living Fossils: How Significant Are They?

Intermediate

It goes without saying that all living creatures are interesting. Some, however, possess an extra mystique. These are organisms which have closely similar counterparts preserved in stone. Obviously a long history has been enjoyed by living examples of such fossil specimens. The living populations are called living fossils. But what about the rest of living creatures, whose preserved remains we do not find in low lying rock? Is their past any different? Let’s delve into the story of the living fossils in order to find out if they are really special and what is their real claim to fame.

dinosaurThe attention paid to certain living fossil organisms leads many people to conclude that these are a rare phenomenon. Such, however, is not the case. Some living fossils have achieved celebrity status because of an element of surprise. They were assumed to have been long extinct and only relatively recently were discovered to be still living. Naturally there has been lots of publicity accorded these discoveries. Among them were the sea lilies or crinoids, discovered in the 1890s to be living in deep sea trenches. Then, the coelacanth Laterimeria was discovered in 1938. Even subsequent landings of this fish have received lots of media coverage. The mollusk Neopilina was first identified in 1956; and among plants, dawn redwood trees were discovered in 1948. Most recently in Nature (Jan. 8, 1998 vol. 391 p. 133-134) there is an account of an early Cretaceous flower Takhtajania perrieri rediscovered living in Madagascar, 85 years after its original identification. The brachiopod Lingula has a different story. Fossils of this organism are found consistently in the rocks from Cambrian levels upward. Today Lingula is found living in restricted habitats. This is a living fossil which does not receive a lot of attention.

The world, in fact, abounds in organisms which merit living fossil status. For example, Peter Ward, in his book (1992. On Methuselah’s Trail: Living Fossils and the Great Extinctions. W. H. Freeman and Company. New York pp. 212) says of mussels, scallops and oysters “Their fossil shells are virtually identical to those of our present oceans.” (p. 67) Moreover Beverley Halstead, in his deluxe 1982 book Search for the Past (Doubleday & Co. Inc., Garden City, New York pp. 208) points out that there are many organisms of common occurrence which actually qualify for living fossil status. Among the diverse creatures which he lists are silverfish, cockroach, monkey puzzle tree, horsetails, Magnolia, lamprey, tortoises and crocodiles, American o’possum and insect eating shrews (p. 196). In addition many microscopic organisms such as bacteria and blue green algae are also identical with specimens in Precambrian rock.

Characterization of an organism as a living fossil basically depends upon the degree of similarity the viewer seeks between living and fossil creatures. If the definition is in terms of general categories of organism, such as sponges in general, or ferns in general, or even specific groups of ferns, then, says Niles Eldredge (Eldredge and Steven M. Stanley. Eds. 1984. Living Fossils. Springer Verlag. New York pp. 291) ” – by such a yardstick, virtually everything is a living fossil.” (p. 3) Whether one allows one’s definition to be this broad or not, it is safe to conclude that living fossils are not rare.

Darwin first drew attention to the idea of living fossils. At this time he was thinking of the Ginkgo tree. From his evolutionist point of view, he was at a loss to imagine how creatures which appeared long ago and therefore presumably have simple characteristics, could do well in communities where the other organisms enjoy the latest developments. It was a wonder to Darwin that archaic or old fashioned forms were not eliminated although they were apparently untouched during the passage of time. From an evolutionary perspective then, living fossils are viewed as organisms with a very long history. Creationists point out that this idea of long time intervals is open to question. Nevertheless, it is the idea that organisms are “very old” which arouses the interest of the public.

Darwin realized that living fossils are not what evolutionists expect to find in nature. Indeed to supporters of the evolution paradigm, the idea of living fossils, so ancient and unchanged, is definitely a problem. As Niles Eldredge remarked: “In the context of Darwin’s own founding conceptions, and certainly from the perspective of the modern synthesis, living fossils are something of an enigma, if not an embarrassment.” (Eldredge and Stanley op cit p. 272) And Peter Ward, in his 1992 book (op cit) terms living fossils “evolutionary curiosities, more embarrassments to the theory of evolution than anything else.” (p. 13)

A number of evolution-oriented works on living fossils have therefore been devoted, for the most part, to damage control: how best to minimize the damaging implications of living fossils for evolution theory. The first technique is to assume that some change has actually taken place. As Eldredge says, no one supposes that the same species which we see today, have actually lasted for long spans of time: “It is fair to conclude, I think, that no one supposes that it is the actual longevity of a single species that underlies cases of extraordinarily low-rate lines of morphologic transformation” (Eldredge and Stanley. op cit p. 275) Because of this prior assumption that modern examples must be different from fossil representatives, the two groups (fossil and extant) are routinely given different scientific names, – at the very least at the species level. Consider, for example, the blue coral Heliopora coerulea which today is a common reef former of the Indo-Pacific Oceans. Very similar specimens make an abrupt appearance in rocks said to be more than 100 million years old. Numerous fossils have been found as well in higher lying rock layers up to the present. A wide variety of species names have been given to the fossil specimens. All of these species however have characteristics within the range of variation of the modern species says Mitchell Colgan (in Eldredge and Stanley. op cit pp. 266-270). Therefore all the fossil specimens should have been given the same name as the modern species. The numerous names accorded the fossil representatives convey an inaccurate impression.

The approach of evolutionists then is to overemphasize differences in order to maximize the appearance of change. For example, of the famous living fossil horseshoe crab, some evolutionists say that the modern species has no known fossil representatives (for example see Daniel C. Fisher in Eldredge and Stanley. op cit p. 205) This statement is based on shell (carapace) shape. As Peter Ward remarked “To a less critical eye, the horseshoe crabs of that long-ago time look virtually identical to present day species. But Fisher found slight differences in the carapaces of the Jurassic and the modern species …” (Ward. op cit. p. 148) Nevertheless Fisher himself admits that compression by overlying sediments makes it hard to figure out fossil shell shapes. ( in Eldredge and Stanley. op cit p. 206) Thus scientists do not really know what the shapes of the shells of former populations were like. This seems a clear case of overemphasizing differences which might or might not be real.

The second method of damage control used by evolutionists is to suggest that unusually slow rates of change are to be expected for some populations. There is a major problem with this explanation however. Evolutionists have not been able to find any general rules which would enable them to predict which organisms might show slow rates of change. Both Eldredge and Stanley comment on this in their 1984 book (op cit) on living fossils. As Eldredge remarked: “Schopf is certainly correct that a number of somewhat different kinds of phenomena underlie our rather casual use of the expression ‘living fossil.’ Some species do have relict distributions (e.g. Sphenodon…), while others patently do not, such as …. Lingula. Some lineages are depauperate in species, such as Limulus and its close relatives, while others generally considered living fossils (such as the nuculoid bivalves …) are relatively speciose. All sorts of combinations are possible …” (pp. 275-276 – omitted phrases refer to pages devoted to each topic in Eldredge and Stanley’s book) For his part Stanley said: “Thus although the punctuational expectation is that living fossil groups should exist, the reasons why some groups rather than others fulfill that expectation can only be assessed on a case-by-case basis.” (Eldredge and Stanley. op cit p. 280)

Another effort at damage control is to suggest that an organism really has been evolving quickly, only the end result is always the same as before. Peter Ward suggested such a situation for Nautilus, an organism characterized by considerable genetic variability. In his book on living fossils (op cit) he speculates about the situation: “Rather than being a prime example of a living fossil, the nautiloids may be examples of rapidly speciating organisms that change only slightly during each [speciation] event, and then return to the same form over and over. The result would be apparent stasis, but the actual history would be similar to that of any other rapidly speciating group – except that the net morphologic change over time would be small, rather than large.” (p. 254) Such a hypothesis would of course, be exceedingly hard to test.

CREATION ALTERNATIVE

From the creationist perspective, the flora and fauna which we see today represent remnants of much richer collections of organisms which lived in the past. The fact that some living forms are different only in detail or not at all from specimens deposited at low levels in the fossil record, raises the question whether any living creatures differ (other than in detail) from their progenitors. Moreover not all organisms which lived at the time of fossil formation, actually left fossils. Living taxa have been identified which lack a fossil record but which are nevertheless considered primitive, close in characteristics to the first representatives of that group of organisms. Examples include Psilotum, an uncomplicated vascular plant, cephalocarids (blind crustaceans) and Peripatus (worm-like).

Secondly the very existence of living fossils calls into question evolutionary assumptions about long time intervals. Two opposite interpretations of the relevant data are possible. The one is that fossilized specimens lived long ago, and survivors have continued little changed since then. Alternatively, it is possible that fossilized specimens were entrapped relatively recently and that populations have not changed other than in minor details in the ensuing time.

The idea of very long intervals with no change, actually makes evolutionists nervous. For example, Wilson Stewart in his 1983 book Paleobotany and the Evolution of Plants (Cambridge University Press see p. 76) remarks that the whisk fern (Psilotum) might have been a contemporary of primitive land plants – but if that is the case, 360 million years have since passed. As this passage of time seems unrealistic, another specialist actually redefined Psilotum as a degenerate fern and thus of much more recent origin. This reduces the problem of a long time interval, but ignores some important information, says Stewart.

Creationists do not have such logical difficulties as they are dealing with a much shorter time frame. Since organisms like Neopilina (mollusk), Sphenodon and coelacanth are all extant today, their fossils could have been entrapped and preserved relatively recently. There is no need to assume incredible gaps in a long fossil record. The case of Neopilina is particularly dramatic. According to evolutionary interpretations, living specimens are separated from fossil representatives by a gap of almost 430 million years. Indeed fossil specimens are almost identical (except for shell thickness) to living specimens. If alternatively, they have since lived in a restricted environment for only a few thousand years, we would not necessarily expect change or higher lying fossil representatives.

It is noteworthy that organisms recognized as living fossils have in certain instances provided a useful check on evolutionary speculations based on the fossil record. The most conspicuous example of this is the coelacanth, which, before living specimens were known, was considered to be related to ancestors of the terrestrial vertebrates. As Peter Ward remarked: “We now know that Latimeria, the living coelacanth, is substantially different from what we suppose the immediate ancestor of amphibians looked like.” (op cit p. 201) Today some authorities promote an altogether different group (lungfishes) for this honour. Nevertheless the former idea was so strongly imbedded in the public mind that we still see traces of it. The Toronto Globe and Mail on January 4, 1960 called the coelacanth a “missing link between man and primitive life.” Thirty years later (October 20, 1990), the same publication used almost identical language when discussing the coelacanth, even although such ideas were discarded long since by scientists.

Living fossils are clearly a topic which merits further research by young earth scientists. When evolutionists admit that they have a problem, then it behooves us to pay attention.

But philosopher of science Del Ratzsch in his book The Battle of Beginnings: Why neither side is winning the creation-evolution debate (1996. InterVarsity Press) suggests that creationists misconstrue evolutionary theory. Dr. Ratzsch suggests that Darwin’s theory has no expectation of inevitable change. Whether there is change or not, and lengthy absences from the fossil record or not, evolution theory accommodates all situations, he says. As we have seen however, some prominent specialists indeed feel that there are features of living fossils which are difficult to explain in terms of evolution theory. As they themselves admit, their explanations are ad hoc in nature and scarcely satisfactory. Research in the recent scientific literature does not support Dr. Ratsch’s criticism of creationary claims concerning living fossils. Let’s not give up this promising source of information.


Margaret Helder
September 1995

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