Leading Researchers Strive to Open New Paths in the Business of Science : ‘Certainty Is Dull, Boring’ to Museum Fossil Curator
Malcolm McKenna has an aluminum ladder stashed on a Montana mountaintop, an expedition planned for Patagonia and access to about 300,000 fossils in storage, all to pursue what he calls the business of science: Trying to show that current beliefs might be wrong.
“The business of scientists is to look for things, not to corroborate previous beliefs, but to keep testing them,” he said. “We keep gnawing away at textbooks and keep destroying what people fondly believe in. We’re trying to improve on the model of reality.”
McKenna, 55, curator of vertebrate paleontology at the American Museum of Natural History in New York, has even found fault with his own theories in the 40 years since he dug up his first fossil. But that’s the business: a succession of theory, contrary evidence, new theory and evidence contrary to that.
This might seem as frustrating as trying to stand on a slippery rock. Not so for McKenna. “Certainty is dull and boring,” he said. “And it’s not really achievable, either.”
A specialist in ancient mammals, McKenna has looked for fossils in places so far north that a compass points south and as far south as Chile and Patagonia in southern South America, where he plans to seek whale bones in the Andes this month. He keeps the ladder atop a 10,000-foot mountain in southwest Montana to reach a productive cliff he found while looking for fossils to help determine the age of some rocks.
McKenna singles out some fossils for study and adds others to the museum’s vast collection, which he estimates is big enough to leave one specimen every 100 feet from New York to San Francisco.
But getting fossils is only part of the job. “We are not stamp collectors,” McKenna said. “What’s fun is what you can do with these things.
“Basically, what we are trying to find out is what has been the natural history of the world. . . . I’m interested in using practically every tool I can to get at that history.”
Different Disciplines
Those tools can come from geology, chemistry, physics, astronomy and other areas as well as McKenna’s own paleontology, which is the study of prehistoric plants and animals. The idea is “to bring completely different disciplines to bear on a problem,” he said. “The cutting edge is interdisciplinary, in my view.”
If different disciplines give the same answer to a problem, he said, “you tend to pick up a little confidence in your results.”
When geological theory suggested that about 60 million years ago, lava spewing from Iceland began to form a land bridge between Greenland and Scotland, it was possible to find confirmation through biology. Fossil remains of crocodiles, turtles, giant salamanders, snakes and other beasts found on Ellesmere Island in far northern Canada show that animals from Europe and North America traveled the land bridge for a few million years.
“The geology and the biology start telling you the same thing,” McKenna said. Pitting one discipline against another “is a way of applying a test, which is what makes it science.”
Theory on Meteorite
Interaction between disciplines produced one of paleontology’s best-known theories: that a huge meteorite struck the Earth 65 million years ago, kicking up enough dust to block sunlight and lead to the extinction of the dinosaurs. The theory is based on a widespread layer of iridium--a substance more common in meteorites than on Earth--which was deposited about the time that fossil evidence indicated that dinosaurs died out.
But McKenna is skeptical. For one thing, few examples of iridium have been found in association with bones of the last dinosaurs, he said. For another, dinosaur species became extinct over time rather than simultaneously, he said. And one paleontologist claims to have found evidence in Montana that some dinosaurs were alive after the extinction date.
Changes in sea level and gradual deterioration of the climate are more plausible explanations for the end of the dinosaurs, McKenna said.
His own current research areas are less likely to capture headlines. One is a study of how mammals, living and extinct, are related to each other, to shed light on the evolution that produced them.
Minute Variations
To uncover the degree of relatedness, McKenna analyzes other scientists’ studies of minute variations between species in the chemical makeup of substances the animals all share. The idea is that the substance had one makeup in some ancestor, then began to change slightly as different species evolved from that common ancestor.
It’s a little like the way a family legend changes over time. If two branches of the family each pass along the story of what happened to great-great-great-grandpa Ed, each version is likely to get more and more unlike the other as it passes from generation to generation. What began as a single story, from the lips of Ed himself, turns into two progressively dissimilar versions.
McKenna is essentially studying that process in substances like myoglobin, which stores oxygen in muscles. By interpreting similarities in the kinds of myoglobin used by three animals, for example, he tries to figure out which two animals have a more recent common ancestor than they both share with the third. From such studies, family trees can be constructed.
Fossil Record Checks
It’s not easy. One of McKenna’s current analyses, for example, deals with about 60 animals, including fish, alligators, chickens, penguins, the duckbill platypus, dogs, horses, sheep, rabbits, two kinds of elephants and man. He is checking the results of the analysis against the fossil record to see if they say the same things about the family tree.
Fossils give their own insights, sometimes unexpected, into how ancient animals were related. When McKenna examined a jaw unearthed recently in Washington state by a Smithsonian Institution colleague, he agreed that the unknown animal was related to elephants. But the jaw had been found in marine sediments, suggesting that it came from an oceangoing beast.
“Suddenly, it dawned on us,” McKenna said. The jaw was from an early order of mammals called desmostylians, which were considered close relatives of the manatees and dugongs that sailors believed were mermaids. Further research by McKenna, Daryl Domning of Howard University and Clayton Ray of the Smithsonian Institution showed that the beasts were actually more closely related to elephants than to dugongs and manatees.
Teeth Were Key Factor
The tip-off was the teeth, which looked clearly elephant-like 35 million years ago when the fossil jaw was formed but lost that character about 10 million to 15 million years ago, the period of previous desmostylian fossil finds.
McKenna did not find the key fossil but, he said: “I had part of the joy of figuring out what it is.” He called that one of the “levels of discovery” for fossil finds, beyond just finding the fossil and recognizing what beast it came from.
Standing in one of the huge rooms where the museum stores fossils, McKenna described “the fun of following your nose” to see what significance a fossil might have.
“There are specimens all around you here that we have no idea of what they mean,” he said. They may be keys to solving a scientific problem, and “we might not even know that problem exists.”
Science appeals to McKenna because “it is so rich in different approaches and different subjects that can be brought to bear on central problems. . . . There’s an awful lot of enjoyment in bringing different approaches to bear on a given problem, to do detective work. Doing the detective work is just plain fun.
‘Open-Minded Stuff’
“Good science is not dogmatic. It’s open-minded stuff,” he said. It is “a testing and therefore humble activity. In a sense, we are willing to admit we are wrong.”
McKenna, for example, did that after he published a paper in 1975 addressing why five premolar teeth had been observed in mammals of 80 million years ago, while only four are seen in modern-day placental mammals. He wrote that some common ancestor apparently made the switch, which was inherited by later generations.
But fossils then showed that a fairly advanced group of mammals still had five premolars. McKenna now theorizes that different groups of mammals lost the fifth tooth independently rather than through a common ancestor.
Theory, contrary evidence, new theory, new contrary evidence.
“You never necessarily get to the end of this,” McKenna said.
