"Scientific Roadblocks to Whale Evolution"
Sherwin at Eureka College
For 50 years before Darwin first published Origin of Species, people had been turning up fossils of ancient whales in great abundance in the United States (Basilosaurus and Zygorhiza). These primitive whales offered little insight into their origin, as they were fully adapted to the marine environment. And it was only at the turn of the century that an older whale (Protocetus) was found in Egypt. Unfortunately, at the time only a skull was recovered.
Because of this lack of evidence of any whales exhibiting any sort of amphibious abilities, they had become poster children of the creationist cause. They offered a unique opportunity in that no one could offer any firm answers as to their origins. Archaeocete whales could be held aloft by creationists proudly proclaiming "See? No terrestrial ancestors, no evolution!" As ridiculous as this may sound, this was what transpired during my first encounter with a creationist.
For the past fifteen years there has been a flurry of discoveries of early cetaceans from Pakistan, India, Egypt, and the southeastern United States. With this, it would seem that creationists would have simply become quiet. However, this is not the case.
With such an ever-increasing amount of fossils and published material, it has become quite difficult for many professionals, let alone interested lay people to keep up to date. And it has become evident to creationists that their readers (and a large percentage of the public at that) are generally ignorant of much that has transpired, and when faced with muddling through technical descriptions, or even just tracking down the journals themselves, most choose to simply ignore it, or else catch a glimpse of it on the evening news.
This has given creationist writers distinct advantages to their (mostly negative) argumentation, or at least toward the people they attempt to "educate". First and foremost, when the evidence is contradictory or difficult to portray in a questionable light, they simply do what the general public does, ignore it. This is easy enough to accomplish due to the fact that very few people will check the references cited.
This leads to another advantage, which is the use of out of context quotes. Many researchers, in writing papers, may call into question the work of others, revise hypotheses in the light of new data, or present past problems, and then go into some detail as to how they have been overcome. Such is the nature of a healthy scientific community.
A good example of the use of an out of context quote is from a recent Institute of Creation Research's (ICR) publication Back to Genesis No. 123, "What They Say" by ICR's founder, Dr, Henry Morris. In it, without going into too much detail, he misquoted Robert L. Carroll from his book Patterns and Processes of Vertebrate Evolution (Morris, 1999a). This "mistake" was brought to the attention of many through an article appearing on the internet and in the Reports of the National Center for Science Education (NCSE) (Britain, 1999). In a response to the allegation, Dr. Morris stated "The error, however, was not one of deception but of presumption. I did not actually have the 1997 edition of Carroll's book at hand, but simply used the quote as I had received it from a constituent." (Morris, 1999b). Regardless of the origin of this deception, it is highly unprofessional to cite a work one has not actually read, let alone quote the author in, or out of context. This is not an isolated incident.
Furthermore, writing in a seemingly authoritative manner without much substance is another way of clouding the issue. Often, there is much editorializing, and political or religious rhetoric that has no place in an article seeking to educate. As we shall see, "Scientific Roadblocks to Whale Evolution" (Sherwin, 1998), which presumably attempts to offer a critique of whale evolution is no exception to these rules.
Today, there is a wealth of published material on any given scientific subject. And in writing on any given subject, it would seem only natural that one would peruse and learn from it before attempting to publish, let alone formulate an opinion.
The Ancestry "Problem"
A number of land animals have been proposed as the ancestors of whales, and some have been way off base. Insectivores, creodonts, and the marine reptiles of the Mesozoic Era (Barnes, 1984) are a good sample. However, Darwin's bear was not really a proposal of ancestry as it is more idle speculation. It turned out to be an embarrassment to him, and was removed from later editions of Origins of Species. After all, such musings have no place in a scientific treatise. Besides, the Cynoidea (or Caniformia, the suborder of carnivores that bears belong to) gave rise to the pinnipeds (seals, sea lions and walruses), other marine mammals.
The answer lies within the ungulates, that much is certain. This includes the orders Mesonychia (extinct predatory ungulates) and Artiodactyla (even-toed ungulates), which are the two front runners in the search for cetacean ancestry. Mesonychians were indeed ungulates (Thewissen, 1994; McKenna & Bell, 1998), even if they live a pedatory/scavenging lifestyle. Both of these orders, along with Cetacea, are paraxonians; ungulates with feet consisting of four toes (originally), with three phalanges each, where digits III and IV are similar in length, and longer than digits II and V, and the loss of digit I (Thewissen, 1998).
A relationship between artiodactyls and cetaceans goes further physiologically. Comparisons of blood composition, uterine morphology, insulin, fetal blood sugar, and tooth enamel microstructure closely ally the two orders (Barnes, 1984), or, in other words, "biochemical, karyological, cytological, and other techniques have repeatedly clustered Cetacea close to Artiodactyla" (Fordyce, et al, 1994).
Molecular phylogenies are also consistent in placing cetaceans with artiodactyls, and in many cases, deeply within the ruminants. In certain sequences, they scored closest with hippopotamids ([y]-fibrinogen introns2-3, [y]-fibrinogen exons 2-4, [y]-fibrinogen exons + introns, cytochrome b, [k]-casein exon 4, [B]-casein exon 7, and protamine P1), and in all cases, secondarily with ruminants (Gatesy, 1998). Unfortunately, it is impossible to extract genetic material from long-extinct animals such as mesonychians to gain further information on cetacean, or mammalian, phylogeny.
As for the fossil material, there are several unknowns. The vascular features of the basicrania (holes and furrows in the skull through which arteries and veins pass) show a closer relationship between early cetaceans and mesonychians than to basal artiodactyls, however, when compared with other ungulates, Cetacea, Mesonychia and Artiodactyla are grouped together, excluding others such as the Perissodactyla (Geisler & Luo, 1998). On the other hand, based upon the astragali (ankle bones), those of cetaceans contain two of the three characteristics that define artiodactyls exclusively: 1.) trochleated head (which cetaceans lack), 2.) sustenacular facet rectangular and covers the entire posterior aspect of the astragalus (also in cetaceans, but narrower), and 3.) ectal facet is reduced and on the lateral side of the astragalus (Thewissen, et al, 1998). These features are lacking in the Mesonychia, but they have remained highly conservative throughout the evolutionary history of artiodactyls.
It is clear that more information from the fossil record is needed to further resolve the issue of cetacean origins, however, this hardly means that they are not descended from terrestrial ungulates.
The Physiology "Problem"
The skeletal features and physiology would not have to, and didn't change radically as Sherwin stated, offering no evidence for the claim, much the same as the quotations from deBeer, Hitching, or Denton. Although I have not read the pieces, the quotes given seem to be either horribly out of date or highly speculative and lacking in any substance regarding, or research into, the subject at hand. This is similar to "Scientific Roadblocks", only with 35, 17 and 14 fewer years of research and discoveries to access, respectively. As stated before, one needs to do research into a subject one intends to write about.
The earliest known whales, Himalayacetus and Pakicetus are presently known only from cranial material, so they are not much help. However, the position of the inner ear bones in Pakicetus are a perfect intermediate between those of land mammals and the rotated ones of cetaceans (Thewissen & Hussain, 1993), not to mention the fact that the tympanic bullae are composed of dense bone as those of cetaceans (Gingerich, et al, 1983).
Neither has the postcranial skeleton radically changed. It is known from the fossil record that in Ambulocetus, the toes are elongated and the femur is short. The other skeletal elements are no different than other land mammals (Thewissen, et al, 1994). At the time of its description, most of the vertebral column and the pelvis of Ambulocetus had not been recovered. It has been, and is awaiting further description (Thewissen, 1998).
However, in the earliest known protocetid, Rodhocetus, there are definitely characteristics that show them to be more whale-like, but hardly radical. These are a further reduction of the femoral length, the rearward migration of the nares (nasal bones), to above the canine teeth (this is true of Rodhocetus, but in Ambulocetus, the narial region is still unknown), the sacral vertebrae are unfused, although they still articulate fully with the pelvis, a shortening of the cervical (neck vertebrae), and probably the most important, are the changes in the caudal (tail) vertebrae. They are relatively shorter, thicker, and more massive than those of land mammals, allowing for better attachment for the muscles involved in powering the, very likely, recently evolved flukes (Gingerich, et al, 1994). With the limb elements still unknown in Rodhocetus, it is not clear as to how much thrust was still generated by the hind feet (as with the majority in "big-footed" Ambulocetus). However, it is possible that Ambulocetus may also have had flukes capable of producing at least some amount of thrust. The extant giant river otter (Pteronura) of South America possesses a horizontally widened tail that produces thrust, even though the caudal vertebrae are of a typical terrestrial form (Fish, 1998). Furthermore, the swimming method of these otters (dorso-ventral undulation of the vertebral column) makes a very good analogy for the swimming method of Ambulocetus (Thewissen, 1998).
The transition of freshwater to sea water has been well-documented temporally through measurements of oxygen isotopes in the tooth phosphates and bones of early cetaceans (then compared with those of modern ones) (Thewissen, et al, 1996; Roe, et al, 1998). But this only tells when they became able to cope with the ingestion of sea water.
Whales, as well as other marine mammals are hypoosmotic, meaning that their body fluids have a lower concentration of salt than their surrounding environment (sea water), and are at risk of dehydration. The major organs in vertebrate bodies that help control osmotic balance are the kidneys. Cetaceans have reniculated kidneys. This means that their kidneys are comprised of lobes, where each lobe has all of the major parts that a single kidney has. Essentially, there is more area to cope with osmotic imbalances. This type of adaptation is not all that radical. Reniculate kidneys are also found in sea otters and some seals and sea lions (Berta & Sumich, 1999), two very different lineages of the order Carnivora. In fact, much of the "fresh" water obtained is through their prey items. Although the reference cited was published nearly a year after Sherwin's article, investigations into the kidneys of marine mammals have been going on since at least the 1930's (The early reference cited in Berta & Sumich was: Ommanney, FC (1932) The uro-genital system of the fin whale (Balaenoptera physalus). With appendix: The dimensions and growth of the kidney of blue and fin whales.: Discovery Rep. 5: 363-466)
Needless to say, in an area such as southern California (like Santee, the home of ICR) where there is an abundance (at least historically) of cetaceans in the nearby Pacific, fossil whales (all up and down the west coast, well, all around the Pacific Rim at that), and universities and museums (UCLA, USC, LA County Museum) one would be able to conduct research into the subject of whales, with detailed literature on the subject existing nearby. So, the physiological barriers needed to be overcome are not as difficult as some would lead one to believe. This problem has been overcome several times in several different manners.
Sherwin stated, or actually quoted, from an encyclopedia no less, "Presumably, various physiological mechanisms for handling oxygen debt and lactic acid buildup, as well as the development of blubber for fat storage and for temperature regulation, evolved early, though evidence of the evolutionary history is unavailable." (Sherwin, 1998, ref. 7). This quote was most likely gleaned for its content of naming several adaptations that, at least to the writer for an encylopedia, have no known evolutionary history, in the hope that the readers of "Scientific Roadblocks" might infer that researchers are clueless as to the nature of these characteristics and how they evolved.
In cetaceans, oxygen debt is reduced significantly simply by their having higher relative blood volumes, and the red blood cells contain more hemoglobin (the molecules that transport oxygen). Oddly, their lungs are smaller on average (and asymmetrical in size) than other mammals. It has been confirmed that air volume in the lungs is nowhere near as important during diving activities as the amount of oxygen bound in hemoglobin (Berta & Sumich, 1999). Also, in dealing with the high pressures experienced during deep dives, and heat conservation, and perhaps to control fluctuations of blood to, as well as acting as an oxygen store for, the central nervous system, whales have evolved retia mirabile (wonderful nets) which are networks of arteries and veins throughout their heads. For a well-documented evolutionary history of these structures, based upon studies of the vascular features of the skulls, brains, and brain endocasts of many whales and ungulates, see Geisler & Luo, 1998 (mentioned previously).
The build-up of lactic acid during times of breath holding occurs mostly when the oxygen stores have been used up and the muscle activity is powered anaerobically. As mentioned above, cetaceans have the capacity to store much higher levels of oxygen, and in most dives, the muscles are powered aerobically. Actually, there is no evidence to suggest that the tissues of cetaceans have any special abilities to handle anaerobic conditions (Berta & Sumich, 1999).
As for blubber evolving early, or any of the supposed enhanced abilities at that, there is no way to document when it happened. It is not known how deep early whales were actually diving (although it could be inferred from the nature of the retia), or when blubber evolved into what it is today, or when the fur of cetaceans was lost. Incidentally, hippopotamids also have blubber similar to that of cetaceans.
Sherwin's statement, "Maintaining a core body temperature while being bathed in an ocean of cold water would be a definite problem for the cetaceans. However, whale fins have fascinating biological structures called counter current heat exchangers [CCHE-mj] to conserve heat" is wholly incorrect. In fact, the CCHE of the dorsal fin actually cools the reproductive system (Pabst, et al, 1995; Pabst, et al, 1998; Rommel, et al, 1998). Regarding this subject, Sherwin quotes from a parasitology textbook and further states that new "structures" cannot arise via natural selection. Without a copy of the book available, it is not clear as to the context of it (perhaps something to do with lungworms, frequent parasites of cetaceans?). However, the quote: "Natural selection can act only on those biologic properties that already exist; it cannot create properties to meet adaptational needs." (Sherwin, 1998, ref. 9)is true to the evoltuion of the CCHE. Furthermore, in another of his references (12- Erwin, et al, 1997), goes into considerable length describing how novel structures have evolved in the past (see below), although it has nothing to do with cetaceans.
Not only is his statement wrong to begin with, but the CCHE's in dorsal fins are not new structures, but the product of paedomorphism acting upon already existing arteries and veins. Pabst, et al (1998: pp. 394-395) state: "We posit that both the intra-abdominal position of the testes, and the vascular structures that form the CCHE in cetaceans, are derived relative to their putative sister taxa Artiodactyla. We hypothesize that these unique features are paedomorphic, and represent a suite of arrested embryonic character states maintained in the adult. Most morphological features of cetacean reproductive systems, however, are shared by members of the Artiodactyla; thus, the majority of the reproductive system reflects cetacean phylogenetic relationships and not novel adaptations to a marine environment."Pabst, et al, 1998)
________________________________________________________________________________________________ It is important at this time to note the wording in the previous quote. "We hypothesize..." All too often, creationists (and once again, the general public) are quick to use the words "theory" and "hypothesis" synonymously with "guess". Let us investigate the basis for this hypothesis that Pabst and her colleagues arrive at.
First (after, of course, training), a search and study of the literature is necessary. One must gain an understanding of the work done previously, and of the reproductive physiology of not just cetaceans and the related artiodactyls, but of mammals in general, and also the nature of fetal development, and the activities, environmental pressures, health aspects, and other stimuli that may affect it.
Second, and most important, is the actual study of the reproductive systems of the animals in question. The descriptions given in Pabst, et al are based upon the detailed dissections of over thirty cetaceans, representing five species of odontocetes and one species of mysticete, throughout various stages of life history (obtained freshly dead via strandings and incidental killing in commercial fishing).
It is through this comprehensive knowledge, trained observational skills, and study of the actual systems in question, that these researchers base their hypothesis. So much for guesswork. They do, however, express curiosity about those cetaceans that do not possess dorsal fins, and comment on a need for further research on them. ________________________________________________________________________________________________
Regardless of the nature of the CCHE, whether for cooling cetacean reproductive systems (Pabst, et al, 1998), countering heat loss in the tongues of gray whales (Heyning & Mead, 1997), cooling through the noses of cats or artiodactyls, or the basic counter-current exchanger of oxygen over the gill membranes of fishes (Hildebrand, 1995), these structures are commonplace, modified from the existing vascular system, and command no hocus-pocus in their evolutionary history, and in fact evolve quite readily.
"Problems" from Head to Tail
Basilosaurus is actually the best known early whale. It is represented by literally tons of fossils mainly from the southeastern US and Egypt, but from many other regions worldwide. So much so, that Basilosaurus is used as an index fossil for the Jacksonian Stage of the late Eocene Epoch in North America (Fordyce, 1992)
And yes, Basilosaurus is not considered to have been ancestral to modern whales, however, in quoting Stahl, Sherwin wrongly lumps "[i.e., Basilosaurus and related creatures]" with "these archaeocetes". There are two families (or arguably, subfamilies) of later archaeocetes; the Basilosauridae and the Dorudontidae. The dorudontids possessed bodies typical of later whales, and very little of their postcranial skeletons differs much from later odontocetes and mysticetes. Well, Dorudon is also known to have had small hind limbs similar to those of Basilosaurus, and their elbow joints were mobile (Uhen, 1998). Most paleobiologists consider the dorudontid stock to be ancestral to the modern suborders of cetaceans.
The dentitions of archaeocetes are heterodont (meaning typical of other mammals in having incisors, canines, premolars and molars), and those of odontocetes tend to be homodont (similar teeth throughout the jaw; peg-like in in dolphins and sperm whales, spade-shaped in porpoises) and also tend to exhibit polydonty (numerous teeth). There are exceptions to this. Many cetaceans have reduced dentitions. The "peculiar serrated cheek teeth" of Stahl (Sherwin, 1998, ref. 11) is not entirely correct. The teeth of archaeocetes did not possess serrations, but series of denticles (cusps), and these persisited, though progressively smaller through time, in many lineages of archaic whales, both odontocetes and mysticetes (Fordyce, et al, 1994), and the heterodont dentition persisted in the squalodontids until their extinction in the late Miocene. Some living river dolphins have molariform rear teeth, and the teeth in mysticetes (resorbed in utero) are heterodont, with typical peg-like ones in the front and ones that bear excessory cusps in the rear (Arvy, 1977).
Although there is no evidence of late Eocene archaeocetes exhibiting telescoping ("strange modification" of Stahl; Sherwin, 1998, ref.11) of the skull, there is a gradual rearward progression of the nares to over the premolar teeth in later species. There are, however, a number of taxa, both odontocete and mysticete, that exhibit transitional stages of telescoping (Whitmore & Sanders, 1976; Fordyce, 1992; Fordyce, et al, 1994), and furthermore, some whose telescoping occurs during growth and maturation, as opposed to this occuring in utero (Klima, 1995). One Oligocene mysticete is currently being studied in South Carolina, from both juvenile and adult skulls, that exhibit this ontogenetic change during growth (Palmer, pers. comm.). Telescoping in cetaceans is an adaptation that coincided with the migration of the nares to the top of the skull. Telescoping, in odontocetes, is the rearward extension of the premaxillae and maxillae bones over the frontals, and in mysticetes, the maxillae extend rearwardunder the orbit (eye socket) forming the infraorbital process (Miller, 1923). So, this "strange modification" of modern whales, not present in late Eocene archaeocetes, exists in various evolutionary stages in their descendants.
The other "problem" presented by Sherwin was the asymmetry of the odontocete skull. Along with telescoping, an adaptation such as this would further aid in echolocation. By this "offsetedness", the echoes returning to the lower jaws at slightly different rates, may give betterdirectional capabilities. Although telescoping, in its various degrees, is known from the earliest Oligocene (ca. 35 mya), asymmetry is not found in odontocetes until the late Miocene (ca. 10-15 mya). Oddly enough, the ability of echolocation may very well have been present in mysticetes. Although it is greatly reduced, vestigial melons are known (Klima, 1995).
The physiology and mechanics of echolocation in cetaceans is an area undergoing a great deal of study today, and there is a lot of literature on the subject. If you're interested in learning more about it (or even cetacean evolution at that), a good word of advice is to look into it from sources that are actually conducting research on it, other than the ICR, or any other organization, religious or secular, that is not.
And now from the poorly researched, to the utterly ridiculous...
"None of the suggested whale's terrestrial ancestors (ungulates or carnivores) have a vertical tail movement. However, whales (and an alleged link, Ambulocetus) do have spinal up-and-down undulation. When did this happen?Where are all the fossils documenting how the side-to-side movement of the land mammal's tail changed to the down and up movement of Ambulocetus (and the whales)?" (Sherwin, 1998). It seems odd that he would speak of the vertebral motion and then compare it with the tail movement. First, the vertebral column of mammals flexes up and down during movement, unlike that of the side-to-side flexure of reptiles. I must admit that the wagging mammal tail offers a much greater problem. We all know how painful it must be for a cat to walk around with its tail straight up, or a dog to curl it between its legs, not to mention barnyard critters swatting flies from their backs. Seriously though, this movement was addressed earlier.
Sherwin's claim that "Pure undirected chance would have to simultaneously produce these horizontal tail flukes independently, diminish the pelvis, and allow the deformed land creature to continue to live and even flourish in the sea." (Sherwin, 1998), is a strawman at best, and at the worst, either an admission of lack of knowledge of the subject at hand, or a deliberate attempt to conceal the wealth of information known about cetacean evolution, paleobiology, and physiology.
The pelves of early whales did not diminish very quickly. Initially, there was a gradual reduction of the size of the hind
limbs. What actually happened to the pelvis is:
I. Pelvic bones are unknown at this time.
II. The pelvis of the holotype of Ambulocetus has been recovered (as well as most of the vertebral column), but is still awaiting description (Thewissen, 1998)
III. Rodhocetus- Pelvis articulates to sacrum, sacral vertebrae are unfused (a major characteristic in the determination of the family Protocetidae) (Thewissen, 1998)
IV. Georgiacetus- Pelvis does not articulate with sacrum, but connected by ligaments (Hulbert, 1998)
Basilosauridae and Dorudontidae:
V. Pelvis does not articulate with the vertebral column, however, the femora articulate to it. And in his monumental 1936 work, Remington Kellogg identified two sacral vertebrae in Basilosaurus cetoides, differing from the posterior lumbar vertebrae by having "dorsoventrally thickened transverse processes that were trihedral in outline, which was not the case in other lumbar vertebrae. This same condition has been observed in Dorudon atrox." (Uhen, 1998, pg. 48)
Mysticeti and Odontoceti:
VI. The pelvic bones are greatly reduced. In some whales, there are also femora present, occasionally lower limb elements, and in rare instances, there are protruding hind limbs. (For a good brief rundown and description, see Nemoto, 1963.)