The Power of Pleistocene Hunger-gatherers: A Forward and Backward Search for the Evidence about Mammoth Extinction

Gary Haynes and B. Sunday Eiselt, University of Nevada

Real Audio Recording   

presented by Gary Haynes

For the last 18 years, my own fieldwork research, both on living elephants and on the fossil record, has been available as support for the idea that climate change alone can explain the fossil record. My coauthor and I have decided that this isn't good enough, so what we're going to do here today is look at it from a different direction.

We've known for 60 years that these well-made chipstone spear points, called Clovis points, are associated with some animals in the fossil record in North America. We also know that there's a large number of these spread out through a range of about 3,000 miles east-west, and almost 3,000 miles north-south. We know that there's about 15 sites where these points, these spear points, are associated with mammoth bones -- and maybe, in a couple of cases, with mastodon bones -- which is not very many. There might be 55, 60, 70 different individual mammoths that died, or were scavenged, by Clovis hunters at these sites.

The question has been raised: Is this a good enough fossil record to indicate overkill or hunting by humans? Or is this scavenging by Clovis people -- finding animals dead during a period of major climatic change? This is sort of the conventional wisdom amongst us archaeologists. There may not be too many of us here. Dave Hurst Thomas is one, and I'm one, and we tend to try to sound a little bit more scientific, maybe, than we should.

But the conventional wisdom is -- or at least it was when I was in graduate school -- that this was a period of great stress for some of the big mammals, or most of them, in North America, and it's in this period that Clovis abruptly appeared -- either dispersing quickly, or technology was introduced amongst a preexisting population. And this was good enough to drive these mammoths and mastodons over the edge into extinction. I'm going to try to limit myself only to mammoths and mastodons here, and not the rest of the fauna.

Some of the ideas, though, that were part of this conventional wisdom have been questioned in the last decade or so, or probably in the last five years. One of the problems with this model is, there are no ethnographic examples of people hunting animals to extinction. They also don't do a lot of other things that we assume Clovis people did. This is what has been called "ethnographic snapshot" -- the use of ethnographic analogy to sort of limit what you can say about the archeological record. This is one criticism that's been leveled at the idea that Clovis people did the hunting to extinctions. There's been others, including some, I think, misapplied examples of foraging theory. This is one example -- marginal value theorem -- which is oftentimes probably misunderstood by archaeologists as the concept that people stop hunting certain animals when they get hard to find. So that, in other words, as animals are becoming extinct, people would no longer select those animals as prey. And I'll come back to these two ideas in a few minutes, after I go through a few more points.

Recent revisions of Clovis, now, have us to believe that, in fact, mammoth hunting was not a major subsistence activity amongst Clovis people. In fact, big-game hunting at all was probably not a major thing amongst Clovis people. I've written this as . . . revisions as two hyphenated words, because, to me, these are only visions; these are not scientific arguments about Clovis. But I want to run through these.

Clovis mammoth sites are supposed to be rare. I think we can refute that pretty easily. I think Paul Martin originally, in his talk here, said something about something that I've told him, that there have been thousands and thousands of elephants killed -- not only in clearing of land for agricultural use, but in culling operations. In 1984, '85 and '86 I saw 9,000 elephants culled, and I cannot find a single site anymore of their bones -- within 10 to 15 years they're all gone. And I saw this happening within three months of every year, over those three-year periods.

So saying that Clovis sites are rare, to me, is actually counterintuitive. In fact, 15 sites with 50 mammoths dead in them to me is an extremely rich, enormously rich, archeological record, of something going on over a very brief period. If it took several hundred years, and there's 75 mammoths, I can understand that being rich, because the three years of culling that produced 9,000 dead elephants had left no fossil, or future fossil, record. And the rest of these ethnographic snapshots -- we cannot find any examples of ethnographic people being observed hunting animals to extinction. We can't find any examples of them doing anything other than generalized foraging. So, therefore, according to this reasoning, Clovis people must have been generalized foragers who did nothing but generalized foraging, and did not bother hunting large animals. And the rest of these -- the fact that there's variability in fluted points has suggested to some archaeologists that all the people making fluted points adopted a technology, but they all different ancestors -- they were already here long before the extinction event occurred.

Now, let me go to my Zimbabwe work, to my own fieldwork, because that's the viewpoint I can tell you the best, or the most about. Most of what I have produced seems to be used to support the climate-change-only model of explaining extinction. Now, admittedly, a lot of it actually does point that way very clearly. For example, if you look at the mammoth sites in the fossil record, and you look at modern elephant sites -- the ones that have been documented during culling or other noncultural death events -- they look very much alike. The same kinds of age profiles are represented in the fossil and the modern elephants; the same kind of geomorphic locations -- not at big rivers or big waterholes, or whatever -- these are at headwater locations, rather small streams.

There's lots of different species represented -- it's not only elephant or mammoth. There's large masses of bone; there's bone that looks like it could be broken artifactually, or broken to make something out of. And another point that oftentimes is not raised when comparing the modern elephant population depletion during the ivory-hunting craze of 100 years ago is that, in spite of the fact that many elephant populations were driven to about zero -- at least to a virtual zero point -- during the ivory-hunting phase of late 19th century southern Africa, they've recovered to some of the highest densities anywhere in Africa within a hundred years. So elephants can recover from overhunting. How could Clovis people, with spear points, have hunted an entire population of mammoths in North America to extinction, if people with high-powered rifles couldn't do it in the late 19th century?

Now, I want to explain some things about the sites, the modern elephant sites, if you're not familiar with what does go on in southern Africa. There are several kinds of sites that I observed being created, by elephants dying either through cultural or noncultural means, and I want to run through these as quickly as I can. Some of the noncultural sites are serial sites, where single animals would die for one reason or another -- old age, starvation, disease, whatever -- and there's quite a few of these on record. Another kind of site, also noncultural -- these are animals dying natural deaths -- are mass death sites. These are jawbones from animals that starved to death in 1995 around one water source here that I've collected to determine ages. And these are rather limited in number, but there are several of them that are known and have been documented for generations.

So these are sites I've been going back to and describing, and trying to understand what death processes are occurring, and trying to explain what the sites look like. This is a site here that contains bones of animals that had died. These are elephant bones in earlier generations, or earlier years of drought, returning to find water. They're not running out of water, they're running out of food nearby to the water.

These sites have some characteristics which are similar, in some ways, to other kinds of sites, but very unique in other ways, and one of the unique things is that the age profile is dominated by subadults -- very young animals. Sixty to 80% of the age profile will be in a noncultural mass die-off, subadults. And another thing that happens is, there's so many dead bodies of elephants around that the scavengers don't generally utilize them very heavily -- so there's very little chewing and scattering and breaking of bones by hyenas, lions, jackals or whatever. And here's an example of a skeleton three years after death. Even the stomach contents are still preserved in it.

Another kind of site are the mass cultural sites -- the sites created by humans who are shooting whole herds of elephants. And I'm not talking about poaching sites here -- I'm talking about legal culling, which has gone through a phase of popularity, and now, currently, unpopularity, in southern Africa. These are attempts to reduce populations of elephants in national parks, where their habitat is perceived to be undergoing change, which is not thought to be something that is to be encouraged. So during certain years in Zimbabwe, large groups -- large numbers of elephants, as I mentioned earlier -- were shot, were destroyed together as herd groups, without selectivity. These are groups ranging from 15 to 73 animals, generally shot by marksmen, and then the rest of the carcasses are salvaged -- the meat, the skin and so on . . . the ivory.

These have their own unique characteristics, too, when compared to the noncultural sites. There's a lot of butchering, complete butchering. There's complete salvaging of the carcasses going on day to day. But it's very rare -- and, in fact, it's been impossible for me to find any sign of that butchering. No cut marks, for example; no chop marks. So the lack of these signs at sites that humans were responsible for is not necessarily an argument in the fossil record against human involvement.

Age profiles tend to be all over the place with elephant herds, just as in any small sampling of humans -- for example, you might get a lot of young and a lot of old in certain groups. But there is a tendency for this kind of catastrophic sort of age profile to show up over and over again, with a few unusual ones, such as this one here. These are four groups that were culled in four different times and places. Lots of young -- typical of a healthy population. And one group, for example, here doesn't have any young, but there is a general trend here towards this kind of decreasing ages, or decreasing numbers at each successively older age group.

There's also a lot of artifacts and fire features around these sites. They're created, after all, by humans, who spend all day butchering. This is a fire pit that's going to be full of ashes. They're usually covered over when abandoned. There's also the odd cigarette butt, the button that falls off of someone's clothes, the lost garment, the lost hat, newspapers and so on. There are plenty of artifacts around these, but I'll come back to this in a minute. The presence of artifacts -- the presence of fire features, for example -- which is quite common in an archeological site, does not necessarily mean the animals were killed by humans. These are also present in noncultural sites.

And, finally, the last type of site that I've been describing are these transported sites, where people have created the sites. They've killed the animals, but they've taken the bones back somewhere to do something with them.

Now, what I wanted to do was find a way of determining how you tell these apart, the different types of sites: the mass sites, the serial sites, the transported sites, the in situ sites, the cultural and the noncultural sites. And if you can tell them apart with elephants, years and years after the elephants have been killed, you might be able to go to the mammoth bone record and tell them apart the same way.

Some of the characteristics are very similar. You can run down this list here. This is the noncultural die-offs of modern African elephants, and here the characteristics of sites that were created by humans shooting them all. But some things are different. For example, the age profile here, is a bit different. There must be some other things that were different, I had decided, and we've run through these and tried to create a scoring system, by assigning points to four different variables.

The variables are the way carnivores use the carcasses -- the utilization of the carcasses by hyenas, lions and jackals, and so on. One point would be very light utilization -- very little chewing and gnawing and disturbance -- and three points would be very heavy. And I scored three other variables the same way -- one, two or three points: weathering; bone representation -- whether some bones have been selectively removed or not -- and age profiling. You've got a list here of the cultural sites characteristics, and the noncultural mass site characteristics -- and there's some slight difference in the total: four points for cultural, seven for noncultural, which is semi-inspiring that there may be some way of separating out these different kinds of sites.

And I did the same thing for serial sites; I did the same thing for transported, as well. I'm not going to show you those slides. But these totals come to some higher numbers, and there is slight separation between cultural and noncultural. And it did become possible -- now, I have to admit that this is sort of a first approximation -- but it did become possible to separate out cultural from noncultural, based on these kinds of scores. Very low numbers were always cultural amongst the African elephant sites that I knew how they were created, and very high numbers were also cultural, and everything in between was noncultural. It also became possible to figure out whether the animals died together, en masse, or one at a time, in series -- with numbers that range, as you can see here in this slide.

Now, the thing to do, and which we did, was to go to the fossil record and try to apply these kinds of analyses to actual mammoth bone accumulations. Here's a selection of sites that have artifacts with them, Clovis points, and a minimum number of individuals of at least five animals -- we tried to have big collections, big assemblages -- and then there's some sites that didn't have any artifacts.

Now, I've called this "cultural" and "no artifacts," but, basically, I'm not trying to make the assumption that just having artifacts means it's cultural, and not having artifacts means it's noncultural. Here's one example of a noncultural site -- or some would argue it's cultural. This is Lamb Spring, in Colorado, that had at least 35 Columbian mammoths in it, and a few other species. There aren't any really good clear associations with artifacts, but there are a few scattered around that may be associated with it. But, basically, it has no Clovis points, so it's questionable whether it is cultural or not. But I'm presuming, at the outset, it probably isn't; and I'm going to let the scoring tell me whether it is or not.

And another one -- the Hot Springs site, in South Dakota, which has at least 50 -- I think 55 -- Columbian mammoths, and a few woolly mammoths in it. There's no artifacts here. This is much older. Lamb Spring, the last slide, was about 11,000 to 13,000 years old; this is somewhere around 20,000 to 26,000 years old.

And the Waco, Texas, site -- this is not very well-reported yet -- but there's at least 22 mammoths in this, (and it's still growing every year) including this one bull, and the rest of them look like females and young, with absolutely no artifacts or features associated with it. So that's at least three that don't seem to be cultural at the outset.

The scores -- well, there are some surprises and some results that just are not surprises. These three up in here are the ones without the artifacts, and the numbers look like noncultural. It's a little bit hard to tell whether they're mass deaths or serial deaths. But the two down here at the bottom, Dent and Lehner, are Clovis sites. Dent has maybe 14 or 15 mammoths in it, and only two or three Clovis points. Lehner has 13 mammoths, and I think 13 Clovis points. And the numbers here suggest that not only are they cultural -- which you might expect, because they have Clovis points -- but they're also mass deaths, which means they died together. A herd of 15 mammoths, and a herd of 13 mammoths, killed by people using stone spears, according to these numbers, if these numbers work as well for mammoths as they do for modern African elephants. So I'll put that up there one more time: They're in situ mass deaths -- Clovis people killing mammoths en masse, and they're definitely cultural.

I wanted to do the same thing with woolly mammoths now -- not to shortchange Eurasian's mammoth extinction event. And some of these sites I have studied myself: Krakow's Spadzista Street in Poland, for example. There's plenty of literature about these sites, such as Mezhirich and Mezen in the Ukraine. So I know some of them firsthand; I could actually do the scoring system firsthand, and I can get enough from the literature to do some of the rest. But I couldn't do all of these. I did a small number -- here's Mezhirich, for example, in the Ukraine -- based on the literature and my firsthand study. And, again, there's some surprises in here, to me. These are surprises to me, because, as I said at the outset of this, 18 years of research has produced results that suggest the fossil record could be explained only by climate change, not by human hunting.

The dwellings in the Ukraine, which have hundreds of mammoths represented by bones, are both cultural and serial. Cultural you would expect, because they're full of artifacts, but "cultural" here means they were killed originally by those people who made their houses out of the bones. Serial is also to be expected, based on the Russian literature -- or the Ukrainian literature -- because the bones are weathered to different degrees, but this is at least some sort of -- call it vindication, I guess -- of people who have thought that the Ukrainian hunters of 15,000 to 25,000 years ago could kill hundreds of mammoths to make houses out of their bones. Krakow's Spadzista Street has 73 mammoths represented by at least 8,000 bones excavated in a 150-square-meter area -- a tiny little bone midden full of mammoths that the numbers suggest were all killed together by people in the Upper Paleolithic. And Berelekh, this is a big surprise, because I don't think there's another living human being who would say this is a cultural site; it's nearby a site, but even the Russians don't believe it is. And, according to my numbers here, these are 166 mammoths -- that's the maximum estimated population of this site -- 166 mammoths died together.

I'll put this one up here again, because this is the two-bone dwellings. These are transported serial and cultural sites. There's no doubt in my mind anymore that people were hunting mammoths, as there had been about 15 years ago. Now the question then becomes: Why would anybody hunt mammoths? Going back to the ethnographic snapshots and the foraging theory models of what's going on here, why would people have done this? Or why would they have hunted all of them, or killed all of them? And what we tried to do here is look at the way foraging theory either can be used to support, or not to support, the idea that Clovis people actually hunted animals to extinction.

There's one model called the "diet breadth model" that has probably been misapplied in trying to argue against people being the agency of extinction, and I'm not going to spend much time on this. Like all foraging-theory discussions, there comes a point where you're sort of engaged in priestly jargon rather than communication about foraging theory, and I know it gets to be very dull. But I do want to say something about specialization, because the argument is often made: If Clovis people are hunting mammoths, they must be specialized -- and, in fact, nobody specializes in hunting big-game animals such as mammoth. Why would they have done this? What needs to be explained here is that diet breadth -- the number of items that are included in the diet -- has nothing to do with people selecting an animal because it's special to them. It has everything to do with making a rational decision based on the returns you get from procuring that particular resource.

So on this graph, we've got diet breadth here. These are the high-rated items, and these are the low-rated items -- and you could see, handling time is very low for a high-rated item. If you kill a very big animal, you get an awful lot of return for the time it takes you to process and eat it. Handling time goes way up here, and that's why these items down here are low-rated. This would be things like grass seeds. You can find grass seeds anywhere, so the search time, obviously, is going to be low for grass seeds, but it could take you a long time to make grass seeds into a nutritious food. Search time might be high for mammoths, but the handling time is low enough that you're getting so many returns it's worthwhile hunting mammoths. And it's been shown -- and it's actually rational to expect -- that the larger the body size of an animal, the higher its ranking is going to be intrinsically. Because it doesn't matter how rare it is -- everybody knows that you get a high return when you've killed that animal.

So what happens in high and low ranking of resources is, it doesn't matter what your diet breadth is -- every time you encounter a high-ranked resource, you take it. You don't turn it down. If you're eating grass seeds and all the rest of this stuff out in here -- the low-ranked items -- when you encounter a mammoth, you will kill it, because you understand that it is high-ranked, because of its return.

Another model is the patch-choice model. Many archaeologists have argued that Clovis hunters would not have chosen the patches where mammoths were all that often -- they would have hunted somewhere else. The patch-choice model is a little bit more complicated than what I'm going to tell you here, but I want to summarize this as quickly as I can. The time you spend in a patch looking for food and the returns are graphed here in three different ways. The time you spend here versus return in this patch type A is what may be expectable in the ocean, for example. If you catch a fish in the ocean, sooner or later another one's going to swim in, and you can just stay there forever and keep on catching fish in the ocean. This type here is also something you wouldn't expect to find very often in a terrestrial ecosystem. The more time you spend, the greater your return -- until you reach a point where there's no more return. If you're going to, say, a nut patch and you eat all the nuts, you basically reach zero return. This patch type down here is probably the most common kind of return that foragers expect. You spend a lot of time in the patch, you get more and more -- but eventually it levels off; it reaches kind of asymptotic shape. And you don't really go to zero, but you go to the point where the return rate is so low that you decide to move to another patch.

Which brings up the question of: What were Pleistocene patches like? I think this is probably the important thing, that many archaeologists who argue against overkill don't really fully understand. They weren't necessarily different in terms of return and time -- they were different in terms of location. And location makes all the difference for foragers, who were trying to get from one patch to the other.

I'm going to suggest here that maybe these Pleistocene patches at the time of Clovis occupation were actually shrinking little refuges separated farther and farther apart by nonproductive areas. And, in fact, they may have been crowded islands -- much like national parks are today in Africa or anywhere else, with sterile areas outside of them -- game sources versus game sinks, as was brought up earlier. They may have been part of a complex mosaic environment, which is what we, I think, understand, as archaeologists, the Late Pleistocene must have been like. And that brings up another series of questions of: What was a mosaic environment really like?

I've got four different suggestions here on how it may have been on the ground a real mosaic: the overlap, the interlock, the concentric and the successional. Overlap -- you can think of this as species A, B, C, moving together so that they have an overlapped area of high productivity. The others you get small areas -- A, B, C, woods, grass, shrubs or whatever. It seems more likely that this is the situation on the ground as it may have existed.

We also know that mammoths were not all that unusual when compared to living elephants, and they probably had very stereotyped diets. And we know from isotopic ecology studies that maybe these patches that were overlapping were rather large in size. And they weren't a question of a few scattered trees here and there with a little bit of grassland -- that they may have been rather large patches of wood next to rather large patches of grass, and they had an area of overlap.

And in these conditions, as had been seen in modern studies, it's bad news for large mammals, in more ways than one. There's a differential kind of reproductive success going on when there's this kind of crowding, or creating little islands. There's delayed maturation in mating -- and all the effects of all of these is to make a large population size actually behave like it's much smaller. There's so much differential reproductive success. And there's even more bad news: It creates situations where older females and very young animals will die first. The older females would, in fact, be the repositories of all the knowledge amongst the elephant herds, for example, or mammoth herds. And trampling, of course -- and there's a number of other things that would be bad news besides just trampling. This would reduce the diversity of the soil biota -- so, from the bottom up, diversity's being attacked.

Which would suggest something about how Clovis people may have been timing themselves. They have been, actually, instead of abruptly going and leaving one patch full of mammoths and going to another, they may have been deciding to stay in them for a long period of time. Now, this is also counterintuitive -- this suggests that people are hunting animals which are rapidly disappearing from the landscape at large, but not disappearing locally at these refuge patches, and hunting them right to the bitter end.

The last slide here is also priestly jargon -- I don't think I'm going to bother too much with this one. But this has to do with marginal value theorem -- that the longer it takes you to get from your patch to the next patch makes a difference in how long you decide to spend in that patch. So people who have to walk from one patch to the next a longer distance will stay longer and create different archeological sites than people who walk short distances from one patch to the next, and get their return, and then go on to the next patch -- because they know the next patch will be productive. This will make a big difference in terms of the size and diversity of archeological remains in an archeological site within the patch.

It won't take very long to find these patches. There's an easy way to get from one place to an elephant die-off, and that's to look for where the elephants are all going. I don't have any time to develop this theme, but this is, in fact, not wasted time, for a forager to follow the elephant trails. They are so easy to see, and it's also quite clear, when you're following on a trail of elephants which are going someplace under stress. And, at the end of the trail, there may not be a big cliff, of course, but there'll be some mammoths there -- and the more mammoths you hunt, the higher your return is going to be, until all the mammoths are gone.

And I don't have a big finish. I do have a small finish. I would like to be able to say this proves that Clovis people killed them, and killed them all, and it wasn't climate. But, of course, we can't do that, because we've been making this argument at each other for a hundred years. So I'll just leave it with the little finish here.

Haynes bio
Eiselt bio