Paul S. Martin, University of Arizona
Q: How do you see the role of humans in causing extinctions?
PM: We see in islands, in our time many cases. The dodo is the most popular illustration of a bird that piqued a lot of curiosity, because it was so strange-looking. The disappearance of the dodo definitely happened in historic time, and it happened for reasons that are more complicated, maybe, than people realize, but had to do with people's discovery of the islands where the dodo lived. The disappearance of the bird soon followed. There are many other situations on the islands in various parts of the world where similar strange birds -- pigeons, parrots and flightless rails -- have vanished during the last few hundred years.
What I'm more interested in -- and what I don't think is as clearly in view because we only could work into the fossil record by virtue of radiocarbon dating over the last 50 years -- is the few hundred years in which an event might have happened. We discovered that fossils -- which we didn't think vanished on our watch, that is, during the time when humans were actually present in the New World -- did. And this is what a great deal of my research has been aimed at -- trying to find out when, and for what reason, animals, from the very largest that we had in America, up until their disappearance -- the mammoths and mastodons, both of them elephants, related to the African and India elephants -- and many other species of large size, like giant ground sloths -- which we simply don't ordinarily think of as being part of the human experience in the New World -- were here. And they vanished at the time when -- or soon after the time -- when the first people came into the New World. Now, that's so much more dramatic than the dodo, or the parrots and the flightless rails that we think of. It illustrates a discovery, looking backward, that affects how we may speculate about events to happen looking forward.
Q: How do you view these prehistoric extinctions in the Americas?
PM: This question fascinated Thomas Jefferson and Ben Franklin. It wasn't clear that the bones that came out of Big Bone Lick, in Kentucky -- which were those of a mastodon -- represented an animal which was, in fact, extinct. And Jefferson, for whatever reason, argued very persuasively that the bones of these large animals -- some of them happened to be bones of extinct ground sloths -- were, in fact, those of animals that we could account for by Indian legends as still being alive today. Part of the Lewis and Clark expedition's mission was to discover these animals. It took a bit of doing, but after a while it was realized that nowhere in the New World, in spite of these wonderful fossils -- and in spite of Native American accounts of a mysterious sort -- did such animals persist. They were only known as fossils. Jefferson's idea of a great chain of being, in which extinction did not occur, was wrong. Then something happened which made people even more inclined to forget about these extinct creatures -- that was the discovery of dinosaurs. What we lost in the process is a view of our history. We should start when people get here, whether they wrote or whether they didn't write. The people, based on this technique of radiocarbon dating, arrived at the time that the mastodons and mammoths, and many other kinds of large animals, disappeared.
That disappearance may be driven by a variety of causes -- and that's what we've been discussing at this meeting at the Museum. It's a vital discussion, because in its resolution will be determined a good deal of what we might plan into the future and how to approach it. If mammoths and mastodons are wiped out by climate, for example, then, perhaps, we should be seriously concerned about certain kinds of climate that might recur, that would match this earlier event. I think that's highly improbable. I personally think that the answer lies in the coincidence of human arrival and the extinction of these animals, and that causality is to be found in that relationship. The basic facts are clear. People established themselves, colonized and spread into the New World at least by 11,000 years ago, if not earlier. And, at this time, large animals -- camels, and extinct species of horses, ground sloths, saber-tooth cats, in addition to mammoths and mastodons, and a dozen or two dozen more genera of large animals -- all go extinct at roughly the same time.
This is something that makes a difference in how we look at our country. If we don't recognize the nature of these large animals, how can we look at what is natural in our landscape? An effort at recovering the Wild West will not be attained by restocking bison and deer and antelope alone, or moose and mountain sheep. Interesting as these animals are, we have to consider the fact that the nature of the country, for long periods of time -- millions of years -- involved a much richer assemblage of animals. We were not only the African Serengeti, we were wilder than the African Serenget until these extinctions occurred.
Q: Did you hear anything at the conference you thought required further exploration?
PM: Well, some of the extinctions didn't happen as fast as I thought they should. The colonizations that occurred in Madagascar took as long to result in extinction as the ones in North America seem to have taken; and North America was perhaps an order of magnitude larger than Madagascar. Why would they be so slow? The same seems true in New Zealand and in Hawaii. The answer may be related to the fact that there's so little change in America after the first colonizations. If the colonizations drove the extinctions of mammoth, camels, horses, how could things be so secure and stable afterward? How is it that the buffalo, or the moose and elk, weren't exterminated at a later time in North America? They weren't. All the change happened at one moment early on.
My answer to this would be based on an idea I have with settlement, with the development of new societies and new lands. We have tribalism. We have intertribal buffer zones, boundary zones, and these intertribal boundaries are places where wildlife will find a natural refuge. This is what we have in Africa now, and had in historic time. And in North America, in the time of Lewis and Clark: where animals were scarce, native people were present in large numbers and not at war with each other. Where large animals were abundant, the reverse was true. The Native Americans around such places were battling each other -- and, in the process, the wildlife maintained a secure population. I suppose a modern equivalent to all of this is the demilitarized zone in Korea, where certain kinds of animals find refuge now and have been studied in the uninhabited, safe zone between two countries, whose wildlife in the occupied parts of those countries is very scarce.
Q: How do you see the relevance of prehistoric extinctions for current biodiversity concerns.
PM: There are probably two answers to that. The first is, if all of this is part of the changes that happened during the history of our anatomically modern species -- and it seems to be -- I think it is very important. It suggests that whatever behavioral nature our species is operating from has been going on for quite a while. What is the reason we have problems now maintaining an economy that's sustained? The same problem was faced by people at a time in the prehistoric past, in my view, when we saw the extinctions that we've been looking at in the fossil record. Sustainability was not occurring at the time that the mammoths and mastodons vanished from North America.
Now, maybe it was climate that drove that change, and then we can absolve ourselves of any need to be concerned about it behaviorally. But if that's not true -- if human behavior is involved -- and I think it has to be, in the case of prehistoric extinctions on all these Oceanic islands, there's not much argument about any other cause. Because each time the extinctions happen in each archipelago, the chronology is different; the timing is different. Human arrivals determine strictly in this dreadful syncopation the sequence of vanishing species. This is on our watch. The reasons for what is in back of all of this I leave to others, but I think it's an opportunity, perhaps, to reckon with the depth of the problem in our time. It's not one unique to our time, and it's not to be trivialized -- it is fundamental.