by Eugene McCarthy
Free download from: http://www.macroevolution.net
Reviewed by Merritt Clifton
Several years ago in an article about pangolins I transiently mentioned the argument of evolutionary geneticist Gene McCarthy that pangolins and armadillos might be living descendants of stegosaurs and ankylosaurs, two related dinosaur families whom McCarthy contends were synapsid proto-mammals, not reptiles.
McCarthy also contends that pterodactyls and pterosaurs were ancestrally related to bats. McCarthy believes that placental mammals emerged much earlier than paleontologists commonly suppose.
In our direct correspondence McCarthy has hypothesized that triceratops and the other ceratopsian horned dinosaurs might have been giant chameleons––which, while a heretical notion, might be possible within the full context of McCarthy’s ideas about how genetic traits evolve.
These ideas and many others about the relationships among ancient and contemporary animals form the entertaining surface of what McCarthy calls “stabilization theory.”
Stabilization theory, which destabilizes what McCarthy terms “neo-Darwinism,” is the somewhat misleading name of a revised theory of evolution which builds on the “punctuated equilibrium” theory presented by Niles Eldridge and the late Stephen Jay Gould in 1972. By “neo-Darwinism,” McCarthy means a dogmatic
belief that evolutionary change occurs primarily and perhaps exclusively through gradual adaptation to facilitate “survival of the fittest.”
McCarthy, a former faculty member at the University of Georgia in Athens, is author of the Oxford University Press Handbook of Avian Hybrids of the World, published in 2006.
“Currently, I’m working on a similar book on hybridization among mammals,” McCarthy says in his online biography–but he told me that “My current project is a novel, a satire of academic life. That’s what I work on eight hours a day. You can think of the things I have to say about evolution as a fossil trace of a former me. I wrote virtually all of my book on evolutionary theory,” On the Origins of New Forms of Life, “twenty years ago or more.”
This appears to explain why On the Origins of New Forms of Life incorporates little or nothing of the findings of recent decades about how viruses and other parasites routinely transfer genetic material among animal species, much as the wind, bees, bats, and birds transfer pollen among plant species.
A further explanation, I learned through e-mail correspondence, is that McCarthy long ago dismissed the possibilities of genetic transfer through viruses and other parasites because such transfers typically involve just a few bits of DNA, in contrast to the high-volume transfers achieved by sexual contact. But McCarthy apparently formed his perspective before virologists learned that some scraps of DNA can activate long chains of recessive traits, to produce significant genetic changes even without significant genetic transfer.
Though McCarthy insisted that “The whole project has lost interest for me, and I’ve moved on to other things,” and was adamant that “I don’t think it would be a worthwhile investment of my time to change a single word,” On the Origins of New Forms of Life has only just begun reaching readers, and presents ideas relevant to current concerns about endangered and alleged invasive species which could only be
strengthened by bringing the presentation up to date.
“During my years at the genetics department,” McCarthy explains in the preface, “I became increasingly dissatisfied with the standard explanation of evolution. The more I read about fossils, the more convinced I became that Charles Darwin’s account of the evolutionary process was fundamentally flawed. Moreover, in my study of hybrids I became aware that an alternative explanation could do a much better job of explaining the available data.”
Like Gould and Eldridge, and many other paleontologists over the past 200 years, McCarthy observed that practically every form of fossilized life ever discovered appears to have changed little, if at all, from the most ancient occurrence of the life form to the most recent. Clear examples of gradual evolutionary
change are few–and many of the examples once thought to exist have been discovered to involve misreadings of the evidence. Also perplexing McCarthy was the lack of a source for “the extreme variation that natural selection would require for the rapid production of new types of organisms, which is mysterious when one thinks only in terms of normalizing selection for adaptive traits.”
McCarthy further could find no explanation in Darwinism for “The origin of complex traits that seemingly have no function in an imperfect state,” before becoming fully evolved. McCarthy was perhaps most perturbed that “Neo-Darwinian theory fails to adequately account for the existence of altruism, since everything is there explained by the selfish needs of the individualŠAn identical difficulty,” McCarthy writes, “pertains to the existence of social insects with distinct neuter forms,” such as worker bees. “How do such forms arise gradually under the influence of selection,” McCarthy asks, “if they do not produce offspring?”
McCarthy found answers to his questions in the genetic mechanics of hybridization.
“According to stabilization theory,” McCarthy explains, “the typical form treated as a species already has all of its characteristic traits at the time it first arises,” as a hybrid of two or more previously existing species. “Individual competition is not an important factor in stabilization theory,” McCarthy continues. Therefore, new species “can be successful and yet be composed of individuals who cooperate and make sacrifices for each other.”
McCarthy developed his ideas into a book, submitted to Oxford University Press in 2007.
“After peer review,” McCarthy recounts, “it was accepted for publication and we signed a contract,” but the unconventional and controversial aspects of stabilization theory eventually caused Oxford University Press to back away from the project.
McCarthy instead published On the Origins of New Forms of Life on his Macroevolution.net web site.
Though On the Origins of New Forms of Life makes scant if any reference to any issues that are controversial outside of academia, McCarthy’s arguments tend to parallel and reinforce my own frequent criticisms of public policies that destroy functional ecosystems and thriving biodiversity in futile efforts to restore the imagined pristine conditions of the distant past.
“Many biologists do not think hybrid animal populations should be treated as named taxa,” McCarthy objects. “They don’t think that organisms of hybrid origin are real ‘species,’ even though the word species lacks a clear definition. For this reason, such populations are often stripped of their scientific names as soon as their hybrid origin becomes known.” Yet, “Thousands of natural hybrid populations have been documented in the animal kingdom,” McCarthy observes, citing a wealth of examples.
“That the introduction of genes from another species can serve as the raw material for an adaptive evolutionary advance has never gained wide acceptance among biologists,” McCarthy suggests, “because it conflicts with a core tenet of neo-Darwinism: the consensus belief that forms treated as species typically arise as gradual change occurs in groups of interbreeding individuals reproductively isolated from other such groups…Neo-Darwinian theory says macroevolutionary change occurs through selection of traits existing within each isolated population.”
This is demonstrably false. “There are about 130 types of waterfowl treated as species,” McCarthy notes. “But there are about 500 different known types of waterfowl hybrids. About 18,000 orchids are treated as species. More than 35,000 types of orchid hybrids are on record, and the number is ever increasing.”
These successful hybrids account for most and perhaps all waterfowl and orchid biodiversity.
Nor are these unique cases. There is genetic evidence that hybridization created the overwhelming majority of fish species throughout the world.
“When zoology was emerging as a science in the eighteenth century,” McCarthy recounts, “practitioners arranged their taxonomies in accordance with an age-old ordering principle handed down from medieval times, the scala naturae. This system had religious roots and pictured beings rising in a linear order of perfection, starting with inanimate minerals and rising through fossils to plants, animals, humans, celestial beings, and, ultimately, God. “In Darwin’s day many people considered rapid change unnatural,” McCarthy continues. “Many, especially those of the conservative upper crust to which Darwin belonged, felt any abrupt alteration was a threat to the social order.”
No family trees
Even as Darwin and other early evolutionists challenged the perceived immutability of the scala naturae, they preserved it in the form of the family tree, the imagined structural model for evolution.
“When different traits are used to construct phylogenetic trees for the same set of organisms,” McCarthy observes, “different trees are implied. Some traits may suggest the relationships of the organisms should be described by one tree, while other traits may suggest the nature of their relationships are quite different. Under such circumstances, the tree that ‘best’ fits the data is selected. But this procedure presupposes that some ‘real’ tree of descent actually exists. If the production of new forms of life via stabilization processes is common over evolutionary time, then there will be no real tree, let alone a best one. The reason: such processes so often involve hybridization that they would give rise to a weblike network of descent, not a tree.”
Of note is that in recent decades the traditional “food chain” of species that eat each other, stretching from bacteria to apex predators and back through the process of decomposition, has given way in science education to the more accurate “food web,” which better describes the complexities of diet.
“Naturalists have long believed that a supposedly treelike pattern of evolutionary history was reflected in the treelike configuration of their chosen system of classification. But this notion may be entirely illusory,” McCarthy continues. “For example, among mammals, flying lemurs are often placed in a separate order of their own, but various authors have also classified them on various occasions as bats, primates, and insectivores. The raccoon dog is placed in the same family as dogs, but is obviously similar to raccoons, which belong to a different family. Scientists have long argued over whether tree shrews are primates or insectivores. Classified as a cat, the jaguarundi resembles a weasel or otter, while the fossa seems to connect the cat family with the civets and genets. Classified as a carnivore, the kinkajou is similar to a primate.
“Under stabilization theory, intermediate organisms are expected,” McCarthy explains. “But under neo-Darwinian theory they constitute a problem.”
Life forms “alleged to be of gradual origin, never seem to be of known origin,” McCarthy continues. “Since even bacteria are known to engage in a form of hybridization, we may reasonably suppose new forms of life were arising by stabilization processes, even in times as old as the earliest strata in the fossil record. There therefore seems to be no need to posit gradual divergence in isolation, even at the very earliest stage of evolution.”
Accurately understanding evolution as the growth of an ever-expanding hybrid web, McCarthy contends, should mean “an end to interminable disputes over whether this group or that one is truly a ‘species.'”
By implication, this would also mean an end to schemes such as shooting ruddy ducks and barred owls, lest they hybridize with “endangered” whiteheaded ducks and spotted owls, who are among their next of kin. Coming to appreciate hybridization would end much, if not all, of the current angst over “invasive” species and an alleged “extinction crisis” which results in large part from species hybridizing successfully to expand biodiversity.
“I can foresee that our children will look back on our discussions of such issues and fail to understand our concerns,” writes McCarthy in his concluding chapter. “They will accept that geographically and morphologically intermediate hybrid populations connect many distinct types of organisms. They will think, too, that our nomenclatural delineations of such populations, if they understand them at all, were largely arbitrary. For they will see that such distinctions have been ruled not only by differences in form, but also to a great extent by the personal prejudices of those who devised the nomenclature and by traditions that ensconced such prejudices on the throne of accepted usage.
“On the basis of stabilization theory,” McCarthy suggests, “we may conclude that evolutionarily successful forms will spawn many offspring forms, heirs to their genes, when they themselves cease to exist. Such forms have a birth and death, just as an individual does. But they are more stable than an individual
because they do not undergo gradual change in the time between inception and demise. Under this view, elimination of certain types of individuals does not result in progress toward perfection. It merely reduces the scope of diversity. Indeed, severe selection against all types deviating from a single ideal would eventually reduce a form to a clone-like uniformity in which no change, progressive or otherwise, would be possible.”
McCarthy imagines “a world in which individual competition and selfishness cease to be biological givens…There is hope in this view of life,” he suggests, “in which nature is no longer ‘red in tooth and claw’…Relieved of the grim duty of destroying our imagined competitors for the sake of mere survival,” McCarthy suggests, “we can rise to a higher moral plane where we, as individuals and as societies, can build ourselves environments filled with ‘sounds and sweet airs, that give delight and hurt not.'”