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FOSSILS

Interview with Dr. Mary R. Dawson

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Dr. Mary R. Dawson is the curator of Vertebrate Paleontology at the Carnegie Museum of Natural History in Pennsylvania and the chairperson of the Division of Earth Sciences. She has led a distinguished career in paleontology spanning 50 years. In part one of our interview, Dr. Dawson talks about her research on early mammals living in arctic environments much warmer than today's.

Where are you from originally?

I'm from the northern part of Michigan, the upper peninsula of Michigan. That was where I grew up, and then went to Michigan State University—which was Michigan State College at that time—for my undergraduate work, and then went to the University of Kansas for my graduate work in paleontology.

How did you become interested in Paleontology?

It started probably with a lifelong interest in animals, and I probably got that from family influences, but I was always interested in animal life. And then I studied zoology as an undergraduate, but also was fortunate enough to be introduced to geology through various courses and had some really fine teachers/professors in both subjects that really were capable of exciting a young student. So after a while I studied a lot of genetics and was interested in how animals got to be the way they are, and then putting the geology and biology together led me into paleontology. So it was sort of an evolution of my interests.

Where you in genetics research around the discovery of DNA?

Before. The genetics that I studied was mostly mouse and fruit fly genetics, and so it was entirely different from the sorts of things they can do now, once DNA was discovered and they're doing all this wonderful work deciphering the genetic code, which is so important.

The other interesting transition is that when I went into paleontology (which was back in the 50's) this was before plate tectonics theory was accepted. So when I was a student, it wasn't allowed to have moving continents. That was absolutely a geological “no-no.” So that was another exciting revolution to live through because we went from a stabilist world to one which was very mobile. And that certainly has affected my interest in paleontology because of my interest in land connections. I'm interested particularly in the northern hemisphere and the land connections across the north Atlantic and of course the north Pacific. That's been a really interesting transition in that interval, too.

These changes were science at its best—adapting to new discoveries.

It really is because I remember as a graduate student we started reading these papers on rock magnetism and trying to trace this wandering pole and it turns out that sure the pole wanders but the continents wander even more. So that was very interesting to watch that unfold.

Tell us a little about your research focused on arctic rodents.

I started out interested in small mammals and did a thesis on the evolution of the rabbit in North America. From there I had a post-doc for a year in Switzerland and there I studied the comparable evolution of the other living family of lagomorphs, that is the pikas, ochotonas.

So that was an interesting complement, because that order (lagomorpha) was a fairly small one so I though well from there I'll go into the rodents which is a very large and very complicated order of mammals and—the rodents and the lagomorphs are what I still tend to specialize in, although I have worked on other kinds of mammals, too. So as far as the kinds of animals, that's what I've specialized in and I did a lot of field work in the western United States as well as some in Europe (mostly aimed at lagomorphs in Europe).

Then in the early '70s, as a result of some plate tectonics information, we got interested in trying to find a fossil record from the area in the north that may have been involved in a land connection between western Europe and eastern North America. That's when we started work up on Ellesmere Island [Canada] in 1973. We didn't find any land animals. We only found fishes in the first season but then two years later we started to find the land animals. That was the discovery of the first terrestrial animals from the Eocene in the Arctic. Then we carried through on that and have been interested in what that group of animals have been telling us about the connections with western Europe as well as—and this is an interesting part of that—that is the environment in which these animals lived.

How was the environment in the Arctic different from today?

Very different. There is a very good plant record from up there and the plants tell us that this was a frost-free area. We have the kinds of plants that suggest that there was no frost, or very little frost. The plants are telling us warm, temperate. And also the animals—we've got alligators and salamanders and big land tortoises and they're telling us the same thing. But the interesting thing [is] you've got a daylight condition. This is well north of the Arctic Circle and even in the Eocene was well north of the Arctic Circle. It was about 75 degrees north latitude in the Eocene, so you've got long, light summers, and dark winters. (It's an environment that's extinct at the present time.) You have to have plants and animals that are adapted to that kind of environment.

In light of climate change today, if you look back millions of years, the climate has changed in ways we would consider drastic, although it happened over long time scales.

Right, that is correct.

So you did find the land bridge that connected Europe and North America?

Basically what we've found is that living conditions at very high latitudes in the early Eocene were suitable for kinds of animals very close to the kinds of animals that lived at mid-latitudes. We've got some really close relationships. But it's not the same fauna. There are differences in composition, they're kinds that are related to those at mid-latitudes, but they're different. So it's possible that the area from which we're finding Eocene fossils (which is mostly on Ellesmere and Axel Heiberg Islands) may have been a cul-de-sac, in other words the actual connection may have been somewhat farther south, possibly Baffin Island to Greenland, although we're not really sure of the course of the connection.

But you do know from looking at the animals from Europe of that age compared with to the animals in North America that there must have been a connection at some time?

Absolutely.

Contrast that with the South Pole and Antarctica based on your research. Isn't there a distinct set of animals there today?

Right. I've never worked down there but there are some animals known from Seymour Island which is just off the Antarctic Peninsula, and those are more closely related to what we know from South America at that time. And of course South America was completely separated from North America. The plant record, also, which is known from the Antarctic Peninsula a little later in the Eocene than what we had in the Arctic—the plant record also suggests connections with the southern continents rather than with the Northern Hemisphere. But, the plant record also is telling us that the Antarctic also was a good deal warmer than it is at the present time. So we've got pretty warm poles in both cases.

Image courtesy of Carnegie Museum of Natural History
Photo by Melinda McNaugher

Related Links:
http://www.carnegiemnh.org/vp/cv/dawson.htm
http://www.carnegiemnh.org/

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