by Kenneth W. Krause.
Kenneth W. Krause is a contributing editor and “Science Watch” columnist for the Skeptical Inquirer. Formerly a contributing editor and books columnist for the Humanist, Kenneth contributes regularly to Skeptic as well. He may be contacted at email@example.com.
If the course of evolution were commanded by a superior intelligence or according to some species-centered notion of progress, humans might reasonably expect to be surrounded by the likes of Stephen Jay Gould. Before his regrettable death in 2002, Gould was a prolific and award-winning author, a distinguished member of the National Academy of Sciences, and Harvard professor of zoology and geology for more than thirty years. But informed laypersons know better than to take such brilliance for granted, thanks in large measure to Gould himself.
After three billion years of unicellular ascendancy, then a mere five million years of Cambrian creativity, the last 500 million years of “variation on set anatomical themes,” Gould argued, “can scarcely be read as a predictable, inexorable, or continuous trend toward progress or increasing complexity.” Natural selection, in fact, has never favored sophistication. Rugged, diverse, and highly adaptable, bacteria (and archaea) are, have long been, and will likely always be the most successful life form on Earth. And what could be more random—more lucky or unlucky depending on your perspective—than death by mass extinction?
Consider the fates of the diatoms and small, rat-sized mammals that lived 65 million years ago, just before the inauspicious asteroid impact off the Yucatan peninsula. Diatoms didn’t survive because they were loved from above or because of their advanced biology. These single-celled players hit the Cretaceous jackpot only because they had previously evolved a seasonal dormancy strategy. Nor were tiny mammals in any way superior to the dinosaurs with which they had coexisted for 100 million years. Only their diminutive stature allowed them to persist and us to subsequently evolve. Complexity, intelligence, and even consciousness, in other words, were begat by nothing more progressive or divine than dumb luck.
But Gould was celebrated as well for his gritty confrontations with fellow intellectuals, zoologist Richard Dawkins and philosopher Daniel Dennett, most conspicuously, each of whom he pejoratively referred to as a “Darwinian fundamentalist” or “ultra-Darwinist” because of their alleged insistence upon interpreting every organismal attribute as an adaptation for reproductive success. Their “adaptionist program,” as Gould referred to it, dogmatically assumed natural selection to the erroneous exclusion of all other evolutionary mechanisms.
With Dawkins, Gould took issue on two fronts. First, the idea that organisms amounted to little more than passive vessels puppeted by genes struggling for reproductive advantage represented, in his estimation, the pinnacle of adaptionism. The “selfish gene” theory, Gould scolded, was “a logically flawed and basically foolish caricature of Darwin’s genuinely radical intent.” Selection acts most prolifically upon organisms rather than upon individual genes, he responded, because significant phenotype modifications are produced only through complex inter-tissue genetic alliances along with environmental factors.
Second, and perhaps more thoughtfully, Gould rejected the claim that “memes,” or professed cultural units consisting of thoughts and behaviors, could evolve at all in Darwinian terms. Biological forms, after all, are drastically more confined than cultures. A platypus, for example, cannot incorporate rat genes to generate a “ratty-pus” lineage because evolution can operate only on preexisting raw materials. Ideas and behaviors, however, can diverge in an essentially Lamarckian mode, borrowing from or incorporating potentially infinite others at any time. Religions, for instance, have frequently interconnected with, hijacked, or simply sponged from independent creeds to form mythological hybrids (if only, as with Christian churches, to deny it later). As such, Gould chided, “cultural change will receive only limited (and metaphorical) illumination from Darwinism.”
The author’s criticisms of Dennett stemmed, for the most part, from the latter’s 1995 attacks against Gould’s pluralist convictions. Dennett, apparently, had denied the dominance of “punctuated equilibrium” (a theory introduced by Gould and Niles Eldredge in 1972 proposing that evolution proceeds in extended periods of relative stasis punctuated by brief intervals of rapid change) over “gradualism” (the traditional Darwinian expectation that significant and directional modification occurs very slowly through geological time) in the creation of new species. But only the theory of punctuated equilibrium, Gould argued, could predict exactly what we have found (and not found) in the fossil record—evidence of overwhelming changelessness and sudden morphological macroevolution among small and geographically peripheral populations. Gradualism alone, he concluded, simply cannot account for the archeological facts.
So too had Dennett maligned the importance of “spandrels,” structural yet non-adaptive by-products of evolutionary change as fodder for later adaptive reuse, or exaptation. Because organisms are profusely complex and integrated creatures, Gould explained, adaptive change always casts off material side consequences akin to architectural spandrels, or the roughly triangular spaces left over between a rounded arch and its surrounding rectangular frame and ceiling. Consider reading and writing, for example. Each must have originated as a non-adaptive spandrel, since the human brain achieved its present size and structure tens of thousands of years prior to literacy. “Taken together,” Gould surmised, “punctuated equilibrium and spandrels invoke the operation of several important principles in addition (and sometimes opposed) to conventional natural selection.”
Arguably, the author was considerably more patient with religious dogmatism. Gould’s now well-worn doctrine of discreet teaching authorities, or “non-overlapping magisteria,” proposed that, because science probes only the empirical realm and religion only moral and spiritual issues, the two should never contradict, less said come to blows with one another. Indeed, Gould offered Pope John Paul II’s 1996 recognition of evolution as confirmation that there can and should exist a “respectful, even loving, concordant between science and religion,” as if the European Church could possibly have continued to deny the unassailable evidence without sacrificing all of its remaining credibility. Regardless, religious dogmatism represents at best only a single stage in the course of moral evolution, and a now-antiquated one at that. History, after all, has abundantly demonstrated the ethical superiority of an empathic, empirico-rational methodology and worldview.
Even so, Gould never shrank from creationist challenges, no matter how misguided or obnoxious. Nor did he take them personally. A consummate scientist, Gould simply seized upon these challenges as opportunities to educate the educable, if not the creationists themselves. Prior to 1994, for example—and still today, no doubt, among ever-inveterate and proudly uninformed young-Earthers—religious demagogues regularly mocked Darwin’s generally prescient suggestion that whales evolved from bear-like land mammals. A few such detractors even managed to ask the helpful and appropriate question—Where are the transitional fossils?—to which Gould and others politely and decisively responded as the evidence became available.
In 1983, Phil Gingerich and colleagues unearthed the skull of Pakicetus from Middle Eocene sediments some 52 million years old in modern-day Pakistan. Although considered the oldest whale, Pakicetus retained certain features in its teeth and auditory structures that appeared to identify it as an ancestor of the mesonychids, carnivorous runners that fed upon fish at rivers’ edges (others suggest that whales are more closely related to artiodactyls). Seven years later, Gingerich found hundreds of partial skeletons including a complete hind limb belonging to Basilosaurus isis, an ancient whale that inhabited Egypt five or ten million years after Pakicetus. Judging by their diminutive leg size, however, these creatures had already made the transition from land to sea. Thus, although an important discovery, Basilosaurus could not serve as a true intermediate. In 1993, though, the hind limbs of Indocetus ramani, another early whale that lived between the eras of Pakicetus and Basilosaurus, were located in India and Pakistan. Clearly amphibious, Indocetus could still support itself on the firmament to which it likely returned to birth and raise its offspring.
Gould’s “smoking gun”, however, arrived in 1994. Slightly younger than Pakicetus, Ambulocetus natans revealed a truly intermediary method of locomotion. Its feet and hind legs were large and robust and each of its toes culminated in a tiny hoof, much as those of its suspected mesonychid ancestors did. Its forelimbs, by contrast, were much smaller and may have served primarily for stability—as with modern sea lions. But the shape of its lumbar vertebrae enabled Ambulocetus to swim in a characteristically cetacean-like manner—by dorsoventral (back-to-belly, as opposed to side-to-side like a fish) undulation. Such motion, Gould noted, is also common among today’s fast and agile carnivores, and was probably so among their ancient counterparts. Last, but not least, Gingerich and company published their description of Rodhecetus karsani, another specimen from Pakistan and perhaps the oldest deep-water whale. Just a few million years younger than Ambulocetus, but substantially older than later whales fully committed to the sea, Rodhecetus bore a shorter hind limb and, like modern whales, unfused sacral vertebrae.
Together these and other fossils display an unmistakable diversity among ancient whales. For Gould, who gushed freely over every satisfying detail, they represented as well the triumph of popular but genuine science over obstinate creationist ideology. No doubt, we’ll miss his enthusiasm no less than his expertise.
As the title implies, The Richness of Life is both varied and penetrating. At one point, Gould stretches well beyond the lay reader’s intellectual grasp. But better his unrivaled acumen should occasionally leave us dry than his communitarian passion ever condescend to our weakness for wanton simplicity. Science has never dispatched a more fluid or informed writer, or one with a deeper sense of social responsibility. Who better than Gould, then, to relay the most exquisite, dreadful—and the most relevant—drama of all time?