Dr. Robert Bakker is one of the most famous paleontologists working today, an iconoclastic figure who has played a leading role of rehabilitating our understanding of dinosaurs from the inception of the “Dinosaur Renaissance” through the present. He is currently the curator of paleontology for the Houston Museum of Natural Science and the Director of the Morrison Natural History Museum in Colorado, and has recently been involved in the study of the hadrosaur mummy “Leonardo.” In 1986 he published the classic book The Dinosaur Heresies, fully bringing his revolutionized vision of dinosaurs to the public, and he has appeared in countless documentaries about prehistoric life. Recently I had the opportunity to ask him a few questions about his work, and what follows are his responses to my e-mail interview;
- [Brian Switek] When I was growing up, I’d see interviews with you on almost every documentary about dinosaurs, and you were even caricatured in the Jurassic Park sequel The Lost World. Has it been difficult, as a working paleontologist, to be so well known as a controversial scientist in the popular media? What are some of the challenges faced by scientists that are not only researchers but also effective popularizers of science?
[Dr. Robert Bakker] Fame is a funny thing. Because my tv appearances are repeated on the tube, my bearded, bewhiskered visage is recycled every couple of months. The latest television documentary, being shot by Discovery Canada, covers the five-year analysis of the duck-bill mummy nicknamed “Leonardo”. This splendid specimen, complete with its last meals preserved in stomach and intestines, is about to go on exhibit at the Houston Museum of Natural Science in September of this year. After a year, Leonardo will return to its home in the museum at Malta, Montana, while a traveling exhibit shares the mummy secrets all over North America.
While trotting through Texas airports, I am recognized by dino-fans, usually in the second-grade to fifth-grade cohort, but sometimes among teachers and high school administrators. It’s still a jolt. Once, in a north Texas Safeway, I was shopping for my field crew when I saw a five-year-old pointing silently at me. I was about to become creeped out when the Mom appeared. “Excuse me…but my daughter says you’re the…..ahem….Dino-Guy.”
I chatted with Mom and daughter and discovered that the child was reading three grades above her level at school. All us dino-scientists have similar experiences. Dinosaurs get kids to read books and think about science. Not just paleo-science but basic chemistry and physics too – plus math and ecology. And history.
Tv appearances help. We can stoke the fires of intellectual curiosity and send kids to the library to find out more. E.g.: Some dino bones are black, some are red – and the contrast should make kids wonder about iron in Jurassic soils, in oxidation, and in how colors are produced by different kinds of ground-water, stagnant versus clean and free-flowing.
- [Switek] At the last SVP meeting in Texas, Jack Horner, Holly Woodward, and Mark Goodwin proposed that the pachycephalosaurs Stygimoloch and Dracorex (which you described in 2006 with other researchers) were really just juvenile representatives of Pachycephalosaurus. What do you think about the hypothesis?
[Bakker] When I first heard Jack explain his extraordinary theory of how “butt-head” dinosaurs changed as they grew from egg to adulthood, I must admit I was thrilled. Here was a story never before told for any dinosaur – or for any land vertebrate animal of any sort. The transformation suffered by the pachycephalosaur skull was so great that no living species could come close to the degree of re-structuring. No antelope, no rhino, no moose, no ground iguana today undergoes such a remodeling of horns and skull roof and openings for jaw muscles (temporal fenestrae).
According to Jack, great, long, sharply-pointed horns could grow out the rear of a bone-head dinosaur for the first half of its life – then, in a complete ontogenetic reversal, these horns would die back, being reduced to tiny remnants as sexual maturity was reached.
Then, as horns disappeared, the flat forehead would begin to grow upward, expanding into a solid dome of bone that rose high over the original skull surface. All the small bones around the eye would be distorted by the dome-growth. Meanwhile, huge temporal openings in the skull would close quickly, so that there was no visible remnant.
If I believed Jack’s theory, three strikingly different skull styles would be merely stages during growth. Dracorex displays no dome, large horns and wide opened temporal holes – therefore it would be a half-grown juvenile. Stygimoloch, has long, curved horns and little dome, and so would be three-quarters grown. And, finally, Pachycephalosaurus with tiny horns and a great, tall, solid dome, would be the ultimate growth stage of the adult.
I’ve been studying horn and dome growth in modern-day critters that butt heads – muskoxen, giraffes, African Water Buffalo. None show anything close to the complete reversal of horn development Jack claimed for butt-headed dinosaurs. And neither did well known horned dinosaurs. Jack had just scored a major coup by discovering a very young Triceratops, a skull that showed the growth trajectory. Triceratops does show dramatic shape changed – but, unlike the pachycephalosaur theory, there was no reversal. Triceratops horns start out small, then grow larger and larger and larger. Triceratops horns never reverse; the horns do not resorb in adulthood, shrinking back to remnants the way Jack thought pachycephalosaur horns shrank.
I brought a bunch of pachy skulls with me to SVP last Fall, new specimens that we are studying. We have a genuine juvenile Pachycephalosaurus, barely two-thirds the length of an adult. According to Jack’s theory, this head should look like a Dracorex, with no dome and long horns. But the juvenile skull has a shape that’s 95% like the adult stage. The horns are small. The temporal holes are gone. And the dome is huge and dome development has distorted the neighboring bones above the eye.
This juvie Pachycephalosaurus is just as small as the Dracorex skull at the Indianapolis Children’s Museum. But the juvenile Pachycephalosaurus had already acquired the definitive Pachycepahlosaurus head structure – it doesn’t look anything like a Dracorex. We have new Stygimoloch skulls too, the same size as the Dracorex. These stygi skulls are not intermediate is shape. They have a small dome and large horns – the diagnostic Stygimoloch cranial configuration.
So……..though electrifying in its novelty, Jack’s theory simply doesn’t work. Pachycephalosaur dinosaurs did grow like Triceratops – or like muskoxen. Bumps and horns simply got bigger and thicker all through life. There was no sudden, dramatic growth reversal. By the time an individual pachy had achieved half-grown size, its dome and horns were taking on the shape that was very close to what the adult would have.
- [Switek] Horner has also been a vocal advocate of the idea that Tyrannosaurus was a scavenger rather than an active hunter. You hold an opposing view of the hunting habits of T. rex and the evolutionary interactions it had with its potential meals. Can you expand the idea of Tyrannosaurus as a fearsome predator?
[Bakker] Jack and my crew are engaged in a friendly rivalry about Cretaceous dinosaurs. Jack’s lab argues that T. rex was a passive predator – an opportunistic scavenger that rarely attacked a healthy, full grown duck-bill or Triceratops. I see it oppositely. Our recent studies of T. rex teeth indicate very unusual adaptations for piercing the armor of horned dinosaurs and ankylosaurs. Most dino-meat-eaters have a long row of sharp teeth, with a few gaps where an old tooth has been shed and a new crown is growing in. T. rex is different. Tooth crowns are immensely swollen and reinforced. Crown replacement patterns produce a snaggle-toothed pattern where single crowns are isolated, with no crown ahead or behind. Result: a rex bite is delivered by a few thick tooth crowns, not a long row of equally tall dental blades.
The rex bite is unique among better known dinosaurs. Instead of inflicting a long, shallow wound, rex jaws would thrust a few crowns deep into bone armor, killing a Triceratops with a single blow. We see close-linked co-evolution here, a terminal Cretaceous arms race. Triceratops is the commonest horned dino of the time, the final dinosaurian Age, the Lancian. T’tops departs from the ceratopsian tradition of frill construction. Torosaurus, very rare during the Lancian Age of the Cretaceous, retains that basic design: the frill is composed of thin bone rods that make a frame, with huge holes in the middle. Triceratops fills in the holes with greatly thickened bone.
Why would Triceratops invest in five times as much bone volume in its frill? Well…to me the answer is obvious. Because the commonest predator has evolved great, armor-penetrating teeth. The argument goes in the other direction – T. rex evolved swollen, tall tooth crowns to deal with the unusual protection of the commonest horned herbivore.
Rexian armor-penetrating teeth would also be useful in overcoming the ankylosaurians – Ankylosaurus itself is twice the body bulk of its ancestors in the American Cretaceous.
Our view of active rexes is paralleled by our interpretation of pachycephalosaurs. The Bozeman group of scholars have concluded that butt-heads din not butt; the cranial extravaganzas – domes and spikes – were merely for visual show. But we find that the neck muscles of all pachy’s are far too strong to be explained by simple passive display. For its body size, Dracorex or Stygimoloch has more strength for dorsi-flexion than a water-buffalo and equal to that of muskoxen. Dorsi-flexion is the action that pulls the head and neck up or resists forces that would shove the head downward. Muskoxen need strong dorsi-flexion because these herbivores ram each other at a full gallop. The tremendous power in dorsi-flexion of pachycephalosaurs demands a theory of kinetic collision.
- [Switek] The recent symposium book Feathered Dragons featured a wonderful essay you wrote about Edward Hitchcock, the man who turned paleoichnology into a science through his studies of dinosaur tracks in the Connecticut Valley. What makes Hitchcock such an important figure in paleontology?
[Bakker] I do have one hero among the early bone-hunters: Edward Hitchcock, President of Amherst and first Director of the Massachusetts Geological Survey. I met him early in my Freshman year, in 1963. I was sitting in the cozy sanctuary at the base of Harkness tower, the Romanesque building that houses the carillon. Carved into the hardwood bas-relief was the unmistakable form of a dinosaur footprint – what was called Grallator by the Reverend in 1836-42.
I knew that Hitchcock was a comic character, so said my dinosaur books. He had “mistaken” dinosaur tracks for those of great prehistoric birds – tee hee! Supposedly he had been deluded by his orthodox Congregationalist beliefs……but…
I got Hitchcock’s original books, his great monograph on Triassic-Jurassic tracks, and I found that his reputation had been twisted. Hitchcock was the first footprint experimentalist for the Jurassic. He ran all manner of beasts, furry, scaly and feathery, over fresh mud to examine their tracks. He scoured the zoo-podiatrical literature, collating all the data on the feet of extant species. No pun intended here – but by 1840, the Reverend knew more about the sole in organic Creation than any other scholar.
Hitchcock was never, ever “mistaken” about dino-tracks. He didn’t assume that the Jurassic footprints were those of birds. He proved that they were birds. Without a single set of fossil foot bones, Hitchcock worked out the number of toes and the number of toe bones and the manner of locomotion among early dinosaurs. His key animal was Anomoepus. Not a theropod predator, but what we now call an herbivorous ornithopod dinosaur, a small, fleet-footed species close in design to that of Hypsilophodon and our Drinker from Como Bluff.
Hitchcock’s diagram of toe joints in Jurassic dinos was computed from the cushiony pads that supported each joint. Each pad marked where two toe bones came together. The number of toe bones, going from inside to outside in the hind foot, was: 2,3,4,5,0. That toe-bone formula marks one and only one Class today: the Aves. Birds.
Hitchcock was the first to show that dinosaurs had small hands with clawed fingers (Anomoepus). And that dinosaurs ran around with high average speed, often in packs. And that the posture was like that of birds – ankles off the ground.
The Reverend never used the word “dinosaur” for his track-makers because the ruling paradigm of the time was that dinosaurs were flat-footed quadrupeds, with rhino-bear-lizard posture. But Hitchcock’s reconstruction in fact matched the real nature of the dino skeleton. The Reverend would have been pleased as punch when the first Laoning skeletons showed that “raptor”-type dinosaurs were, indeed, covered with feathers.
- [Switek] Finally, as someone who works with the “bones of contention” and the fossil record, what do you think about the current controversy surrounding evolution in the United States? How can we do a better job of communicating science to the public?
[Bakker] We dino-scientists have a great responsibility: our subject matter attracts kids better than any other, except rocket-science. What’s the greatest enemy of science education in the U.S.?
No way. It’s the loud, strident, elitist anti-creationists. The likes of Richard Dawkins and his colleagues.
These shrill uber-Darwinists come across as insultingly dismissive of any and all religious traditions. If you’re not an atheist, then you must be illiterate or stupid and, possibly, a danger to yourself and others.
As many commentators have noted, in televised debates, these Darwinists seem devoid of joy or humor, except a haughty delight in looking down their noses. Dawkinsian screeds are sermons to the choir; the message pleases only those already convinced. Dawkins wins no converts from the majority of U.S. parents who still honor a Biblical tradition. Hitchcock is a far better model. He had his battles with skepticism. He did worry that the discovery of Deep Time would upset the good people of his congregation. But Hitchcock could view three thousand years of scriptural tradition and see much of value – and much concordance with Jurassic geology.
Read his “Religion of Geology“. It’s a lovely contemplation of how Old Testament and New deal with the beauty in Nature. And the horror. Why is there pain and death among deer and lions? Why is there pain among humans? These questions are of little interest for the Dawkinsians, but trouble most Americans. Hitchcock found no easy answers. But he saw a Plan nevertheless. Millions of years of geological time, with waves after waves of predator and prey, punctuated by extinctions, were recorded in the sedimentary annals.
Careful study of fossil history gave Hitchcock a sense of awe – and privilege. He was a human being during the scientific revolution, fortunate to live at a time when society was awakening to the possibilities of understanding past ecosystems. Petrified jaws and teeth did prove that Nature was always regulated by attack and defense, pain and death. But the net result was extraordinary beauty that could be made intelligible by the human mind.