I think of the old spiritual: “Sometimes I get discouraged, and think my work’s in vein. But then the Holy Spirit revives my soul again.” I’m actually a fairly cheerful soul, but we all need replenishment now and then. If “there is a balm in Gilead” (the song’s title) for scientists, that elixir, that infusion of the holy spirit, takes the form of new discoveries. on the very week of my essay’s publication, Phil Gingerich and colleagues (see bibliography) published their description of yet another intermediate fossil whale, a fifth tale for this gorgeous sequence of evolutionary and paleontological affirmation. (I did feel a bit funny about the superannuation of my essay on the day of its birth, but all exciting science must be obsolescent from inception — and I knew I could write this epilogue for my next book!)
Gingerich and colleagues discovered and named a new fossil Eocene whale from Pakistan, Rodhocetus kasrani (Rodho for the local name of the region, kasrani for the group of Baluchi people living in the area). Rodhocetus, estimated at some ten feet in length, lived about 46.5 million years ago. This new whale is thus about 3 million years younger than the “smoking gun” Ambulocetus (Case Four and the key story in the main essay), and about the same age as Indocetus (stage three in the main essay). No forelimb bones have been found, and the spinal column lacks tail vertebrae, but much of the skull has been recovered with, perhaps more important, a nearly complete vertebral column from the neck all the way back to the beginning of the tail. Most of the pelvis has also been found and, crucial to evidence about intermediacy, a complete femur (but no other elements of the hind limb).
We may summarize the importance of Rodhocetus, and its gratifying extension of our story about “hard” evidence for intermediacy in the evolution of whales from terrestrial ancestors, by summarizing evidence in the three great categories of paleontological data: form (anatomy), habitat (environment), and function.
FORM. I was most struck by two features of Rodhocetus’s anatomy. First, the excellent preservation of the vertebral column provides good evidence of intermediacy in a mixture of features retained from a terrestrial past with others newly acquired for an aquatic present. The high neural spines (upward projections) of the anterior thoracic vertebrae (just behind the neck) support muscles that help to hold up the head in terrestrial animals (not a functional necessity in the buoyancy of marine environments; whales evolved from a terrestrial group, the mesonychids, with particularly large heads). Direct articulation of the pelvis with the sacrum (the adjacent region of the vertebral column) also characterizes both Rodhocetus and terrestrial mammals (where gravity requires this extra strength), but does not occur in modern whales. Gingerich and colleagues conclude: “These are primitive characteristics of mammals that support their weight on land, and both suggest that Rodhocetus or an immediate predecessor was still partly terrestrial.”
But other features of the spinal column indicate adaptation for swimming: short cervical (neck) vertebrae, implying rigidity for the front end of the body (good for cutting through the water as the rear parts of the animal provide propulsion); and, especially, the seamless flexibility of posterior vertebrae (sacral vertebrae are fused together in most large terrestrial mammals, but unfused in both modern whales and Rodhocetus), an important configuration for providing forward thrust in swimming. Gingerich and colleagues conclude: “These are derived characteristics of later archaeocetes [ancient whales] and modern whales associated with aquatic locomotion.”
Second, and even more striking for this essay’s case of graded intermediacy, sequentially discovered during the past twenty years, Rodhocetus is about 3 million years younger than the “smoking gun” Ambulocetus (a marine whale with limbs large enough for movement on land as well), and a good deal older than later whales that had already crossed the bridge to fully marine life (Basilosaurus, my Case Two, with well-formed but tiny hind limbs that could not have functioned on land, and probably didn’t do much in water either). In the most exciting discovery in this new Case Five, the femur of Rodhocetus is about two thirds as long as the same bone in the older Ambulocetus — still functional on land (probably), but already further reduced after 3 million additional years of evolution.
[ Adapted from Douglas Futuyma, Evolutionary Biology, New York: Sinauer, 1998, p. 196. ]
HABITAT. Rodhocetus is the oldest whale from fully and fairly deep marine waters. The oldest of all whales, Pakicetus of Case One, lived around the mouths of rivers; Ambulocetus and Indocetus of Cases Three and Four inhabited very shallow marine waters. Interestingly, the more fully marine habitat of Rodhocetus correlates with greater reduction of the hind limb, for Indocetus is a contemporary of Rodhocetus, yet grew a larger femur comparable in length with the earlier Ambulocetus. (All three creatures had about the same body size). Thus, admittedly on limited evidence, limbs decreased in size over time and became smaller faster in whales from more fully marine environments. (Perhaps Rodhocetus had already ceased making excursions on land, while the earlier Ambulocetus, with a larger femur, almost surly inhabited both land and water.) In any case, the contemporaneity of Rodhocetus (shorter femur and deeper water) and Indocetus (longer femur with life in shallower water) illustrates the diversity that already existed in cetacean evolution. Evolution, as I always say, no doubt to the point of reader’s boredom, is a copiously branching bush, not a ladder.
FUNCTION. Rodhocetus lacks tail vertebrae, so we can’t tell for sure whether or not this whale had yet evolved a tail fluke. But evidence of the beautifully preserved spinal column — particularly the unfused sacral vertebrae, “making,” in the words of Gingerich et al., “the lumbocaudal [back to tail] column seamlessly flexible” — indicates strong dorsoventral (back to belly) flexion at the rear end of the body — the prerequisites for swimming in the style of modern whales (with propulsion provided by a horizontal tail fluke, driven up and down by bending the vertebral column). I was particularly pleased by this result, since I closed my essay with a mini-disquisition on multiple adaptive peaks and the importance of historical legacies, as illustrated by vertical tail fins in fishes vs. horizontal flukes in whales — both solutions working equally well, but with whales limited to this less familiar alternative because they evolved from terrestrial ancestors with backs that flexed dorsoventrally in running. Gingerich and colleagues conclude: “This indicates that the characteristic cetacean mode of swimming by dorsoventral oscillation of a heavy muscled tail evolved within the first three million years or so of the appearance of the archaeocetes.”
A tangential comment in closing. The sociology of science includes much that I do not like, but let us praise what we do well. Science at its best is happily and vigorously international (see essay 20) — and I can only take great pleasure in the following list of authors for research done in an American lab based on fieldwork in Asia, supported by the Geological Survey of Pakistan: Philip D. Gingerich, S. Mahmood Raza, Muhammad Arif, Mohammad Anwar, and Xiaoyuan Zhou. Bravo to you all. I also couldn’t help noting the paper’s first sentence: “The early evolution of whales is illustrated by partial skulls and skeletons of five archaeocetes of Ypresian (Early Eocene) . . . age.” The geological time scale is just as international, for our fossil record is a global scheme for correlating the ages of rocks. So a layer of sediments in Pakistan may be identical as representing a time named in a place that later became the bloodiest European battle site of World War I — the dreaded Ypres (or “Wipers” as British solders named and pronounced their hecatomb).
But so much for lugubrious and sentimental thoughts. Let’s just end in the main essay’s format for our new case of Rodhocetus:
CASE FIVE. Open and shut.
Verdict: sustained in spades, wine and roses.
Magazine Skeptic Interview
Stephen Jay Gould
An Urchin In A Haystack
An Interview by Michael Shermer
How does one briefly summarize the life of an intellectual like Stephen Jay Gould in a short introduction? He has been praised to the hilt by skep
tics and humanists for his tireless efforts in battling the creationists, admired by writers and reviewers for his brilliant literary style, and read by virtually everyone with any interest in science, from layman to professional. After an A.B. from Antioch College and a Ph.D. from Columbia, Gould began teaching at Harvard at the young age of 26, and immediately set to work to reform his profession. In 1972, he and Niles Eldredge published their theory of punctuated equilibrium, a new interpretation of the fossil record, and Gould won the prestigious Schuchert Award for excellence in paleontological research by a scientist under age 40. Like his baseball hero, Joe DiMaggio, whose 56-game hitting streak is considered one of the most remarkable achievements in the history of sports, Gould began a streak of his own of monthly essays in Natural History magazine. At the time of this writing it is up to 256, and he intends to continue it to the end of the millennium. For his literary achievements Gould has won countless awards, including a National Magazine Award for his essays, a National Book Award for The Panda's Thumb, a National Book Critics Circle Award for The Mismeasure of Man, the Phi Beta Kappa Book Award for Hen's Teeth and Horse's Toes, and a Pulitzer Prize Finalist for Wonderful Life (about which he characteristically commented, "close but, as they say, no cigar.") For his scientific achievements Gould was made a Fellow of AAAS, received a MacArthur Foundation "Genius" Fellowship, and won "Scientist of the Year" from Discover magazine. He was voted Humanist Laureate by the Academy of Humanism, received the Silver Medal from the Zoological Society of London, the Edinburgh Medal from the City of Edinburgh, and the Britannica Award and Gold Medal for dissemination of public knowledge. He has fought the two "Big Cs"--creationism and cancer--and beaten both: the creationists all the way through the Supreme Court, and abdominal mesothelioma cancer, now in remission.
Yet being on top of the scientific and literary world has a price-- one becomes a tempting target for critics, and lately Gould has accumulated more than a few, and no slouches are some. In Vol. 3, #4 Richard Dawkins told Skeptic: "I think that punctuated equilibrium is a minor wrinkle on Darwinism, of no great theoretical significance. It has been vastly oversold." In the November 30, 1995 issue of The New York Review of Books, John Maynard Smith concluded: "Gould occupies a rather curious position, particularly on this side of the Atlantic. Because of the excellence of his essays, he has come to be seen by nonbiologists as the preeminent evolutionary theorist. In contrast, the evolutionary biologists with whom I have discussed his work tend to see him as a man whose ideas are so confused as to be hardly worth bothering with, but as one who should not be publicly criticized because he is at least on our side against the creationists. All this would not matter, were it not that he is giving non-biologists a largely false picture of the state of evolutionary theory." Daniel Dennett, in Darwin's Dangerous Idea, devotes an entire chapter to critiquing Gould, sarcastically referring to him as "America's evolutionist laureate," and suggesting that Gould's politics have significantly influenced his science. In light of these recent criticisms, Skeptic asked Gould to clarify the record on a number of scientific, religious, political, and personal issues.
Steve Gould turned 54 last September, and has recently gone half- time at Harvard, dividing his energies between Boston and New York (and between the Red Sox and Yankees, with an ultimate devotion to the latter). But don't think this means Gould will be slowing down. The urchin--Gould's own metaphor of a though exterior that prickles the enemy--is buried in the haystack, always searching for generalities among life's particulars. The essay streak continues, his travel and lecture schedule is relentless, and his scientific work is now being channeled into his "big book" on evolution that will synthesize past and present theory. So with that, America's evolutionist laureate synthesizes his own past and present.
Skeptic: I'll begin easy and move toward more controversial questions. What essay are you up to now in the streak, and when do you plan to end it?
Gould: It's about 256 essays, and I'll end it January, 2001. When you've got a millennial transition, why not take advantage of it? That will be about 330 essays.
Skeptic: In the long history of baseball there has been quite a colorful variety of commissioners, including a Yale professor of literature. How about a Harvard paleontologist?
Gould: I have no administrative skills. Being a successful commissioner of baseball requires prodigious people skills, which I absolutely do not have. I've never administered anything. I've never even chaired a committee.
Skeptic: Despite the fact that you obviously care little for publicity, fame, or public adoration, you have become one of the two or three most famous scientists in the world, in constant demand for your time. How do you deal with that?
Gould: By maintaining a very rigid private life. It's funny. Different people have different attitudes towards it. That's what I like about being in New York--it is such a sophisticated city. If people recognize you in New York they are as likely to make some wise crack, like "Hey Gould, you punctuated my equilibrium today showing up here." That's fine and I just laugh back. What I can't stand is people who come up to me and say, "Oh, are you Stephen Gould?" Fortunately that doesn't happen much in New York.
Skeptic: In talking to publishers about the marketability of science books to the general public, they seem to feel there is only room for a few names to be commercially successful, such as yourself, Carl Sagan, Stephen Hawking, and a few more. Why is it so limited?
Gould: I think there is actually more room than that. It really is just a commercial question of how many people want to read about science. I think John Brockman is basically right in his Third Culture book--though I think he takes it a bit far since he is the agent of most of these guys--but there is a hunger among intellectual people for scientific knowledge, in the sense that literary culture's old hold upon arbitration of taste and interest has faded and that, in fact, many science books have done well and that indicates that the public does want to read them.
Skeptic: We've heard rumors of your "big book" on evolution. What's the status of it? And give us a brief summary.
Gould: I've got a thousand pages written--it's about two-thirds done, and I hope to complete it in about two years, but definitely before the millennium. It will be structured like my first book, Ontogeny and Phylogeny. The first half will be history of science. The second will be modern views. I start off discussing the belief that some hold, that theories cannot have essences. I then show that this is almost nihilistic--it doesn't make sense because under that criteria the intellectual line of Darwin is Darwinism, but suppose it turns into its opposite? If an animal turns into its opposite you can still trace its history, but if those who are the intellectual descendants of a theory come to agree the opposite, then it is no longer the original theory. In other words, I think theories do have essences, but the problem of claiming that something like Darwinism has an essence is that people argue over every feature.
My solution is to try to find a middle position between nihilism and the position of Hull of overspecifying something to the point where you will argue about it forever. To me, the essence of Darwinism is a three-legged stool: gradualism, extrapolationism, and causal efficacy of natural selection (and therefore variation is only raw material and does not contribute through its structure to causality). You really need all three of those. If natural selection is efficacious but works at higher levels, that's not Darwin's formulation. If natural selection is efficacious but it cannot be extrapolated through time to understand the pattern of life's history, that's not Darwinism either. Those to me are the minimal conditions of the essence of Darwinism.
The interesting thing to me about modern evolutionary theory is that each one of these three elements needs to be expanded or enlarged. It's not that they are wrong--natural selection is a creative force, it does work on individuals, and it can sometimes be extrapolated. But none of the three levels is sufficient by itself in its narrow definition. In the case of natural selection working on individuals, the hierarchical theory of natur
al selection is an important revision. On the question of natural selection as a creative force, some studies, particularly from developmental biology, have illustrated important constraints on the nature of variation. And everything from punctuated equilibrium to mass extinction theory provides important revisions to gradualistic extrapolationism.
So, the first half of my book argues that all three of these reforms--the hierarchical theory of selection, the notion of important constraints coming from the internal structure of organisms, and the catastrophist alternative--really have ancient pedigrees. These are not new conditions. These are parts of the grand argument.
Skeptic: So there is an essence to Darwinism, which you identify. What does your revision of that essence do to it? Does it change the essence?
Gould: No. It shows that you need an expanded and enriched theory that is based on a hierarchical model of natural selection, a recognition of the power of internal factors, and catastrophism...
Skeptic: So you see yourself adding to the essence of it, not revising it completely?
Gould: No, its a revision. It's a different theory that doesn't negate the importance of Darwinism, but it is quite different from the ultra-Darwinism of Dawkins and Maynard Smith. They want just the straight and narrow. There's nothing wrong with the straight and narrow, it's just not nearly enough to render all of evolution...
Skeptic: So, just as Einstein adds to Newton without changing the essence of Newtonianism...
Gould: I wouldn't be so grand to make that analogy, but in a sense, structurally, that's not a bad analogy.
Skeptic: When I first entered the history of science profession I found that you were one of the few scientists writing about the history of science that historians read. They really respect you. The history of science profession is a bit of an old boys' club and they don't think scientists have much of interest to say about how science is done. But you have broken through because you are sensitive to social influences and the cultural context of science, so I wanted to ask you how you came to that, since most scientists are not sensitive to the biases of the culture and themselves, and what are some of the influences in your own life?
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