March 18, 2005 | David F. Coppedge

Horse Evolution Is Back on the Charts

The old horse-evolution charts from the 1880s have been revised substantially since 1920 when paleontologists began to realize the story was not so simple.  (Thomas Huxley had used the series of O. C. Marsh as a focal point of his 1876 lecture tour in the United States.)  These charts portrayed small horses with three toes evolving into large horses with one toe.  Jonathan Wells wrote in his 2001 book Icons of Evolution that Darwinists have been more forthcoming about the horse series, in trying to set the record straight, more than with any other alleged proof of evolution.  This is evident in many museums, like the Natural History Museum in Washington, which instead of showing a straight tree of descent, exhibits more of a branching bush pattern, and points out that the old picture was inaccurate (see 03/02/2001 story).  Nevertheless, in Science this week,1 Bruce McFadden (U of Florida), a world export on horse paleontology, entitled his review article, “Fossil Horses—Evidence for Evolution.”
    It’s not that evolutionists ever denied horses descended from a common ancestor; they just revised the path evolution took.  The idea of orthogenesis (straight-line evolution), popular in the late 19th century, has given way to the paradigm that evolution by natural selection takes an undirected, random path.  In addition, the fossil evidence for horses has shown that some of the assumed ancestors and descendents were, instead, contemporaries.
    McFadden wrote the definitive book on horse evolution 13 years ago: Fossil Horses: Systematics, Paleobiology, and Evolution of the Family Equidae (Cambridge Univ. Press, New York, 1992).  Has the picture changed at all since Wells listed it among 10 “icons of evolution” that persist as myths more than proofs?  (See summary of argument on  Surprisingly, McFadden labeled his revised phylogenetic tree, “Adaptive radiation of a beloved icon” (emphasis added in all quotes), and used the phrase again in his conclusion:

Fossil horses have held the limelight as evidence for evolution for several reasons.  First, the familiar modern Equus is a beloved icon that provides a model for understanding its extinct relatives.  Second, horses are represented by a relatively continuous and widespread 55-My [million-year] evolutionary sequence.  And third, important fossils continue to be discovered and new techniques developed that advance our knowledge of the Family Equidae.  The fossil horse sequence is likely to remain a popular example of a phylogenetic pattern resulting from the evolutionary process.

The evolution of which McFadden speaks is not simple variation – after all, there is a great deal of size and shape variation among modern horses, from Shetlands to Clydesdales – but macroevolution, or “higher level (species, genera, and above) evolutionary patterns that occur on time scales ranging from thousands to millions of years.”  Here, he is convinced, horses remain the definitive case: “The speciation, diversification, adaptations, rates of change, trends, and extinction evidenced by fossil horses exemplify macroevolution.
    To the chart: what picture does McFadden exhibit compared to the old icon?  Like Wells, he debunks orthogenesis:

The sequence from the Eocene “dawn horse” eohippus to modern-day Equus has been depicted in innumerable textbooks and natural history museum exhibits.  In Marsh’s time, horse phylogeny was thought to be linear (orthogenetic), implying a teleological destiny for descendant species to progressively improve, culminating in modern-day Equus.  Since the early 20th century, however, paleontologists have understood that the pattern of horse evolution is a more complex tree with numerous “side branches,” some leading to extinct species and others leading to species closely related to Equus.  This branched family tree (see the figure) is no longer explained in terms of predestined improvements, but rather in terms of random genomic variations, natural selection, and long-term phenotypic changes.”

The figure shows most of the fossils being contemporaries of one another in the upper third of the timeline, with grazers and feeders and browsers “exhibiting a large diversification in body size” scattered among the branches.  Only Hyracotherium and Mesohippus occupy the basal position in the tree.  Yet Wells pointed out that orthogenesis is still implicit in the new charts, regardless of the side branches, if there is a trunk leading from eohippus to Equus.  And he emphasized that both paradigms, straight-line and branching evolution, remain philosophical positions rather than observations.
    To the bones: what new fossils and revised interpretations of old fossils justify McFadden’s assertion that the horse series exemplifies macroevolution?  The complexity of the horse evolution picture becomes apparent when he points out that only one genus, Equus survives, while three dozen genera and several hundred species have gone extinct.2  Furthermore, most of the alleged macroevolution occurred in North America, where horses went extinct but survived in the Old World.  What evidence has come to light since the “branching bush” paradigm replaced the old icon?  While diversity is evident, macroevolution seems a matter of viewpoint:

Although the overall branched pattern of horse phylogeny (see the figure) has remained similar for almost a century, new discoveries and reinterpretation of existing museum fossil horse collections have added to the known diversity of extinct forms.  Recent work reveals that Eocene “hyracothere” horses, previously known as “eohippus” or Hyracotherium, include an early diversification of a half- dozen genera that existed between 55 and 52 Ma [milli-annum, million years] in North America and Europe.  New genera have recently been proposed for the complex middle Miocene radiation, although the validity of these genera is still debated.

The truth is in the teeth, he concludes: “Horse teeth frequently preserve as fossils and are readily identifiable taxonomically.  They serve as objective evidence of the macroevolution of the Equidae.”  Yet his discussion reveals that, although the teeth of these animals display considerable variety, “The tempo of this morphological evolution has sometimes been slow and at other times rapid.”  The final third of the chart shows groups branching out with teeth designed for grazing and others designed for browsing or feeding on both grasses and leaves.  What he terms “explosive adaptive diversification in tooth morphology” appears to have doubtful justification, since most of the species on the chart overlapped in time.
    McFadden mentions nothing else in support of horse evolution, but spends a paragraph debunking an old evolutionary myth: Cope’s Rule.  Cope and other early evolutionists seemed to assume bigger is better: ancestors were small, descendents got larger over time; “this notion is now known to be incorrect,” he says.  In his chart, horses got larger at first, but since 20 ma ago, “In contrast, from 20 Ma until the present, fossil horses were more diverse in their body sizes.  Some clades became larger (like those that gave rise to Equus), others remained relatively static in body size, and others became smaller over time.”  Nevertheless, as stated earlier, he concludes on the positive note that “The fossil horse sequence is likely to remain a popular example of a phylogenetic pattern resulting from the evolutionary process.”  But is a popular example the same thing as an expert’s example?

1Bruce McFadden, “Fossil Horses–Evidence for Evolution,” Science, Vol 307, Issue 5716, 1728-1730 , 18 March 2005, [DOI: 10.1126/science.1105458].
2It must be recalled that identifying species from fossils is highly subjective, since interfertility cannot be established; today’s quarter horses and Belgians might be assigned to different species based on skeletal remains, yet are interfertile.

What’s wrong with this picture?  The horse evolution icon, like Rasputin, has been shot, stabbed and drowned, but is taking his time to get dead.  Here is one of the classic proofs of evolution, explicated by Mr. Horse Evolution himself, and are you convinced?  Saying this is proof of evolution doesn’t make it so.  Better look this gift horse in the mouth.
    Consider some salient points.  (1) Extinction is not evolution.  If a creature abruptly appears in the fossil record, survives for a time, then goes extinct, no evolution has occurred, in the macro sense.  (2) If animals appeared and existed as contemporaries, they cannot be arranged into ancestral relationships.  (3) If they existed on different continents, it becomes a stretch to assume they shared genetic information.  (4) Assigning skeletons to different species is a highly subjective process – and therefore subject to one’s presuppositions.  (5) The dating of these fossils assumes evolution and long ages – a case of circular reasoning.  (5) Variations in teeth adapted for different feeding habits reveal nothing about the origins of teeth.  Teeth are very complex structures (see 03/13/2003 and 06/04/2002 entries).  (6) Terms like “explosive adaptive diversification” assume evolution; they explain nothing about how random mutations could have produced simultaneous morphological changes that all had adaptive value.  (7) Interestingly, McFadden omits any mention of horse toes.  The old picture showed three-toed horses evolving into one-hooved horses of today.  But even that begs the question of whether one toe is better (or more evolved) than three; it almost seems backward.  Duane Gish in Evolution: The Fossils Still Stay No points out that in the evolutionary story of ungulates, the picture is reversed: ungulates supposedly evolved three toes from one.  (8) The basal clade Hyracotherium has doubtful relationship to horses at all.  Its position in the horse tree is merely for evolutionary wish fulfillment, to put something in the blank.  If omitted, most of the rest of the Equidae become contemporaries.  Furthermore, there is a big gap between Hyracotherium and anything preceding it, so where did it evolve from?  (9) McFadden’s analysis only considers size, teeth, and location.  How did the remarkable capabilities of the horse, like catapulting legs (01/02/2003) and damping muscles (12/20/2001)arise by chance?  (10) If you think this story is pathetic, the whole mammal phylogenetic tree is a mess (see 05/28/2002, 12/03/2003 and 03/18/2003 entries).
    In the Peanuts cartoon, Linus once asked Lucy to read him a bedtime story.  Exasperated by his persistent pleas, she blurted out, “A man was born, he lived and he died.”  Linus contemplated, “Makes you wish you could have known the fellow.”  Dry bones in the ground don’t say much.  Evolutionists, unsatisfied with the starkness of the raw data, enjoy the entertainment of weaving fanciful tales in between the bones.
    In short, McFadden seems committed to rescuing his beloved icon from the withering attacks of both creationists and other evolutionists, so that he can announce triumphantly in Science that the rockets’ red glare and bombs bursting in air only serve to give proof through the nighttime of data that the icon is still there.  But enough of storytelling.  Get a horse.  Go for a ride and clear your head of evolutionary confusion.  Horses are wonderful animals, full of grace, humor, expression, strength and majesty.  Learn some incredible things about horses in the new film Incredible Creatures that Defy Evolution III.  Thank God for the horse, one of man’s most capable and faithful companions on earth.

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Categories: Fossils, Mammals

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