I want to begin with some thank-yous. I want to say, first of all, thank you to my good friend and excellent adversary, Paul Martin. In a real sense, the reason that a lot of us are even here today is because of the groundbreaking work of Paul, his colleagues and students, over the last 30 years. Thank you, also, to our international visitors -- to Richard Holdaway, Tony Stuart, Norman Owen-Smith and Tim Flannery, who fought jet lag and dialectical differences in English to make their data and interpretations so lucid for us.

Likewise, thank you to the home talent -- to John Alroy, Paul, of course, Gary Haynes, Russ Graham, Dave Burney, Helen James, Douglas Siegel-Causey, and Stuart Pimm, who did us very proud with their expositions. Thanks, also, to my American Museum colleagues -- to Niles Eldredge and Melanie Stiassny, who, as usual, not only enlightened but entertained. And to the people who actually put all of this together -- the CBC staff.

About 20 years ago, the well-known ecologist, paleontologist and general Renaissance person, Leigh Van Valen, wrote a series of papers which usually included a phrase: "the other half of biology." What he was particularly concerned with, at that point, was the apparent overdomination that was beginning to occur with molecular approaches and, say, non-organismic approaches to understanding the diversity of life. And what he was telling us was that we must not forget that other component -- and I think, nowadays, we haven't. This kind of audience, this kind of interest in this subject matter, is a tribute to that point.

What I am here to tell you is that we must, in fact, not forget about the other half of the other half. Leigh was talking about evolutionary biology in the large sense, but with particular reference to what we call the production of species -- all of the events concerned with making the diversity of life as we know it. But extinction is as much a part of the pattern of life as evolution is. And whereas we think we know a good deal about the speciation process, and other things of that nature, I'm going to argue that we know much less than we need to about extinction.

In line with that, my job this morning is to present a summary of some of the deliberations yesterday. I'm going to attempt to put a bit of a spin on it, in that I'm going to try and relate it more to the concerns of today. But what I'm interested in getting out to this audience is the notion that not only do we have a lot to learn about extinctions in general, but it really does behoove us to learn a great deal more, and understand a great deal more, about extinctions in near time.

I've divided this talk, in a very rough way, into deep time, near time and future time, to reflect the fact that extinctions that happened very far back are interesting to look at, very briefly, because a lot of people think that the big problems there have been solved. That's all a question of bullite impacts, anoxic turnover, worldwide glaciation, and so on. But, in many respects, the data are as complicated as anything we have to deal with, both in the very near-time extinctions -- the ones in the last 40,000 years -- or, even more important, the extinctions that are going to take place in the future.

I'm beginning with this slide to make the remark that, as in life, generally, things happen. And the things that have happened in the course of life on this planet is that the biotas have been repeatedly shaped as much by extinction as by any other process. Niles Eldredge made that point crystal clear for us yesterday in giving us a brief introduction to extinctions in deep time, some of which were almost of unimaginable extent -- like the one at the end of the Permian. The spike speaks for itself. At least, according to one estimate, and one way of looking at the data, up to 95% of all marine species living at that point in time disappeared.

The most famous deep-time extinction that we've heard about is the one at the K-T boundary, 65 million years ago. There was an impact by some large extraplanetary body that smacked into the earth and set in sequence a cascading series of effects that, among other things, resulted in the extinction of all nonavian dinosaurians. This idea was proposed by Walter and Luis Alvarez in the early 1980s. They're seen here on the road to their discovery.

The dynamics of this, however, are still very obscure. It is the case that we have facts -- we have the facts of the impact in Yucatan. I think God is telling me something -- that, according to at least some estimates, the amount of release of, say, noxious gases or particulate matter into the upper atmosphere; the creation of mile-high or multimile-high tsunamis, and so on and so forth, created the equivalent of a hypernuclear winter that lasted at least for a decade. And during that time, of course, caused the collapse of terrestrial ecosystems and, apparently, accounted for at least some extinctions. The marine realm also had some deep effects there, as well.

Coterminous with this, there was apparently a great deal of vulcanism in parts of the world, and some people think that these events were related -- which makes sense, if they were close in time. Or that one precipitated the other; the impact precipitated the vulcanism. But there are a lot of other things that are still quite uncertain. One is: Why was this extinction a little bit selective -- in the sense that one large group or a couple of large groups, if you don't believe in dinosaurian monophyly -- why were they so severely impacted, that, basically, we only have the birds left?

Cooper and Penny in a recent article -- using molecular techniques and a particular data set and a molecular clock -- estimated that at least a hundred vertebrate lineages made it past the K-T boundary, including a number of things that, if they were, trophically speaking, anything like what we know they should have been like, it's hard to understand why they made it. My point here is that, even for these most thoroughly researched and apparently well-understood extinctions in deep time, we certainly don't have all the facts, and we don't have, perhaps, the correct interpretations even now.

Let me now switch to extinctions that are much closer to us -- the extinctions in near time, which I'm defining as the time since anatomically modern humans came onto the scene at least 40,000 years ago and, according to at least some kinds of investigations, probably two or three times that. The actual number in millennia doesn't make much difference right now.

Yesterday was devoted to trying to make sense of pattern, and that is what a lot of this is all about -- that we have a fact body; we have ideas that come in from all kinds of directions, including what we think we know about how the planet is organized presently. And by judiciously choosing among the kinds and sorts of pattern elements that we think are important, we come up with ideas, hypotheses that, in the optimal case, are testable and tell us something.

There's something else about patterns, however, and that is that we expect patterns to repeat themselves if all of the boundary conditions are in place. Perhaps not in the infinitely detailed manner of a fractal image, where you have the same patterning at all levels of magnification, but at least something close to that. So that when we see the same things happening again and again, we believe that it is correct to conclusively conclude that we know what's going on. We have to be a little bit careful, however. We have to be careful about how those facts are put together and how the conclusions are drawn from them.

Here's a pattern that is probably shouting something at us, and it's the next pattern I want to look at. This is the pattern of now, and the implications for the future. This was developed several years ago by Walter Reed. There are many images like this, and they are all showing us roughly the same thing -- which is, in this case, mammal and bird extinctions rising at a dramatic rate as we pass up toward the modern period.

Now, if we had no sense of time, we might conclude, incorrectly from this, that this is the only pattern we need to have in mind; this is the only pattern we really need to think about. What's going on right now is the thing that is important. And we can solve everything we need to solve, in terms of understanding that pattern, merely by looking at what's in front of us, or for data sets that are only a few centuries old. But let's ask another kind of question. If we've been on the planet for 40,000 years, is it reasonable to think that all of the impacts are due to modern, technologically advanced society? That what we're seeing here, for extinctions in the last 500 years, can be completely explained simply by what modern people are doing to their environment?

There are several possibilities about the past. One possibility, suggested by the middle graphic here, is that, in fact, the extinctions in the most recent era are the ones that are the most severe in content, the ones that involve the most kinds of losses, and that although there were extinctions in the past at some kind of background rate, they were not as dramatic as what we're facing right now. Another possibility, suggested by the lower image here, is that there have been many extinctions in the anthropogenic past, some of them perhaps on a scale that matches, or even exceeds, what we think is going on now. I am here to tell you today that that last pattern is the fact pattern of history, and it behooves us to understand it better than we do.

I want to begin with this map from a paper by Paul Martin several years ago. It's color-coded to show you where and when extinctions of dramatic size, particularly affecting mammals, happened during the last 40,000 years. The pattern is very interesting. In yellow, in Africa and Eurasia, the two continents of oldest human residency, there were extinctions, but they tended to be small in number and smeared out over a very long period of time. The losses were not of a dramatic sort. About 40,000 years ago -- perhaps earlier, as was explained to us -- that pattern of loss or, rather, a pattern of loss, begins to be seen, first in Melanesia, in Australia and New Guinea. Many large mammals were lost at that point, and other kinds of vertebrates, as well.

About 10,000 to 12,000 years ago, the scene switches over to the continental Americas, at which point there were a whole series of extinctions -- apparently very closely correlated in time, maybe in a period of less than four centuries -- with a yield of at least 135 mammalian losses. Finally, the eve of destruction in this historical pattern falls on the last remaining large habitable places on earth, the islands of the West Indies, central Mediterranean, Madagascar, New Zealand, the Pacific.

There are two arresting features of this pattern. One is that it very, very closely tracks the human diaspora. As far as we can now tell -- although I recognize this is a matter of great controversy among anthropologists -- people like us didn't get out of Africa and Eurasia until roughly 40,000 or 50,000 years ago. Thereafter, they went sequentially in time -- although the groups were, of course, different -- to Melanesia, to the New World, to the islands, both small and large.

The second arresting feature is that the tracking of the losses was almost identical to the tracking of these extinctions. So, for example, 10,000 to 12,000 years ago, an extinction was immediately preceded by the first arrival, as far as we can tell, of people in the New World. Subsequently, all of the large islands of the world, beginning with the West Indies 7,000 years ago; Madagascar, perhaps 2,000 years ago; New Zealand, perhaps only 800 years ago -- losses followed immediately subsequent to human arrival. The pattern, we all agreed yesterday, I think, is undeniable, but what kind of explanatory overprint are we going to put on it? How was it accomplished, and what lessons do we need to learn from this?

The dreadful syncopation that I'm referring to here is what I, at least, call "first-contact extinctions." The pattern we have to explain most is why it is that the losses don't seem to occur until people are on the spot. If we were talking about any kind of normative system in which extinctions can come and go according to all kinds of causes, then surely we would see overprints in time of these other kinds of disappearances. Although there were some people -- some presenters yesterday -- who argued that, although people might have been incidentally important, there were other causes, particularly climate change. I think, still, the tenor of the evidence is that, in most times, in most places, it was not anything that we would call natural. That is to say, anything other than anthropogenic.

There are many "design features," as we might call them, of these extinctions in near time. I'm going to hasten a little bit, since I've already talked about several of them. They are bove background rate -- clearly not globally synchronous, in the sense that the extinctions in Madagascar happened thousands of years after those in the New World, and, again, thousands of years after the ones in Melanesia.

Other interesting points were the fact that, at least with respect to mammals, it was large-bodied forms that were most seriously affected. And that continues to be a point of leading interest in trying to understand these extinctions. Again, if it was a normative kind of thing -- as John Alroy brilliantly demonstrated for us yesterday, with respect to Cenozoic extinctions, in general -- why should it be that at no other time except in these Pleistocene losses, or Quaternary losses, was there a very definite selection for large body size? Prior to that, extinctions seemed to more or less generally affect things across the body-size spectrum. That is an outstanding feature that requires explanation.

And another point of certainly technical interest -- although it has yet to find a full explanation, and this is not something that I want to go into in detail now -- but this notion of the lack of replacement. Other extinctions in time, by and large, involve other animals and guilds coming in and replacing what's disappeared. Well, that clearly hasn't happened this time. Is it because evolution just hasn't caught up with the process? Or is it because the whole thing has been so dramatically altered, in the way that Tim [Flannery] told us about for Australia, that maybe all of the boundary conditions and laws that used to exist before humans came along have been breached? And we're into a brave new world that none of us really understands.

Here I want to just give you a global -- and, again, very quick -- overview of a thing that came up again and again in conversation, and I think is desperately important for understanding these extinctions. Gary Haynes made the point in talking about mammoth extinctions that it's location, location, location. He's a secret real-estate agent. What he was thinking of was that in order to understand details about extinction, you have to know the data intimately -- and, in many cases, the data that we're talking about are bones in the ground. You have to understand how things are deposited and how to interpret them properly.

Well, I would say that, yes, that's important. But what's even more important for understanding these extinctions is timing, timing, timing -- which is a point, again, that Paul Martin made for us decades ago, but continues to be true. That, thanks to our ability to date these events -- through radiocarbon, chiefly, but with other methods coming along -- we can speak meaningfully about this syncopation: the arrival of people, the immediate and subsequent loss of species. Before there was the ability to put a finely detailed chronology on all of this, there was no reason to think that there was any particular kind of cause, anthropogenic or otherwise. For all anyone knew, these extinctions were smeared out over a very large time interval, and there could have been any number of explanations. So timing is, therefore, dramatically important.

And what do we see? Well, the Australian case continues to be obscure, in the sense that there were many extinctions, but a lot of the taxa that have disappeared remain poorly dated. Tim has, I know, several projects in mind about how to improve this situation. But the long and short of it is that it is possible that that extinction event was, in fact, a multimillennial one. We need to know more, especially given the kinds of information that are now available for that continent and its losses.

The locus classicus for all of this, the Americas, seems to be falling more and more into the pattern that Paul advanced years ago, which is that these losses happened extremely sharply. Nothing that was presented yesterday, with respect to the Americas, seems to go against this pattern -- although Russ Graham argued, I think extremely well, for his position that climate change was an influential factor; that range reductions continued over a long period of time might also have had their effect. Others of us, like John Alroy, thought quite differently and had their own arguments to back up their positions. Nevertheless, as far as the radiocarbon chronology goes, it looks like that extinction event was short, sharp.

It's also of interest to look at extinctions much more recently in time -- the ones in Madagascar, in which about two dozen vertebrates disappeared, -- again mostly of very large body size. Dave Burney, who has spent much of his career working on that island and trying to sort out what's going on there, gave us reason to think that perhaps, there, too, there was some smearing. Although, again, we're talking about shorter and shorter intervals as we get along up to the present. People may be only 2,000 years old in Madagascar in terms of human habitation, and it may be that it took 500 or 1,000 years to complete those extinctions, but Madagascar is a large place. And, perhaps, if it was the same kind of event that it was in the Americas, the pattern continues.

What interests me greatly are the extinctions that happened at or shortly after the 500 BP mark. They interest me because, as I tried to argue yesterday, there's something a little bit paradoxical in what a lot of us are thinking and saying about extinctions in near time. If it was largely people -- and that's all right -- then those people who were forcing these extinctions were, in terms of their tool kits, not like us. These are not people with nuclear reactors; these are not people who pollute on a scale that is nearly unimaginable; these are not people who are draining the world's resources on a scale that is nearly unimaginable. These were people who themselves, to a much greater degree than is true today, were a functioning part of nature, in a way that Niles described for us. How was it, then, that they dramatically managed to bring down -- if that is what happened -- so many different kinds of animals, so quickly, in at least the kind of pattern that we're seeing in the Americas?

Well, you can look at recent extinctions and find support for that idea, and information that is not very supportive of it. I think supportive of it is the history of island faunas in the last few hundred years. There are so many examples that I hardly need to make the point -- the point is extremely well-known. That in place after place, the losses -- due not only to human direct impacts, but to their introduced species, to the things that they've let run wild, like cats, mongooses, and pigs and rats, and so on -- have almost certainly had an extremely severe impact on native faunas. Mauritius being a classic example, a place that was not discovered, not occupied by people, until the modern era, and within the past 400 or 500 years, something like 30 vertebrate extinctions.

Going against the pattern, however, I would argue -- with mammals, at least -- is that the number of extinctions in the last 400 or 500 years have been very different from the pattern of losses at these earlier times. Megafaunal species, in fact, have not been hit hard from the point of view of complete extinction. Of course, from any other viewpoint, they've been hit extremely hard. But they haven't been driven to complete extinction, except in a small number of cases -- roughly 10. The overwhelming number of extinctions have occurred in Rodentia, in Insectivora, in Marsupialia -- small mammals, for the most part. What we're experiencing now is a minifaunal extinction.

Again, there's several ways to look at it. One way that's very reasonable -- I think this is one way that Tim and I would probably agree -- is that if we're talking about aftershock, what we're talking about is a world that is now a series, ecologically speaking, of raw and open wounds, in which we have lost many of the things -- from the vertebrate point of view, at least -- that made those ecosystems work. And we have a lot of space fillers. There's not a lot of species that take the really good jobs, like Niles told us about yesterday. And maybe what we're seeing clicking through is this extinction process now working itself out, down to lower body sizes. It's a possibility. It is also possible that the extinctions that are going on now are different, not only in scale but in type, from those that occurred earlier.

I'm going to now go through for you some of the arguments advanced by presenters yesterday. I obviously can't do justice to them all, and I'm not even going to try. I'm going to tell you about the things that I think are worthy of attention, because they're part of the pattern, and part of the pattern that we all have to come to grips with. Just for the purposes of this talk, I'm going to divide these into what I'm calling "direct impacts" (anthropogenic overhunting sorts of things) versus "indirect impacts," in which people, in some sense, may have been causes, but perhaps not the final cause of what was going on. Also, I will be including explanations that really don't feature people as the primary factor, including the climate-change argument.

I've told you that the pattern begins, in one sense, in the way that we currently understand it, in Melanesia, with extinctions beginning on the order of 40,000 years ago. Throughout, the pattern of direct impacts is difficult to trace -- and this is something that came up a little bit yesterday, although there was less chat about it than we might have otherwise entertained. And that's the problem of what you actually think you're looking for in detecting direct impacts.

Paul has the position that maybe we shouldn't expect to find very much -- meaning that we shouldn't expect to find this kind of 12,000-year-old horizon, in the case of Americas, where you're seeing all of these megafauna down in droves with arrowheads sticking out of them. In other words, the extinction might have happened so quickly that we can't expect to find the smoking pistol, and that overkill is still quite consistent with what went on -- even though finding what we would, at least in a court of law, regard as direct causation is not there.

In the case of Australia, there is almost nothing of a direct sort that really supports the idea of overkill. Instead, it's all the rest of the pattern features that are consistent with it. In the case of the Americas, there is perhaps a good deal more. There are a number of sites that are interpreted as kill-off sites, particularly of things like mammoths, in various parts of North America. Some of these are associated with artifacts, some aren't. Gary Haynes did a very interesting treatment of these different kinds of sites, and the expectations one might have of finding different patterns of features and different kinds of things that would lead you to believe that they could be conclusively considered to be kill sites -- as opposed to die-off sites, meaning that the animals were dying for reasons other than direct impacts by humans.

I think, of all the places on the planet where this pattern reaches its zenith -- because nearly everything is consistent with the overkill argument -- is New Zealand. Richard Holdaway gave us an incredible amount of food for thought with respect to how the extinctions were mediated there. I think, again, going back to the theme of timing, one of the critically important things is the discovery -- and I do mean discovery -- in the last few years that there really was no Quaternary signal, in the same sense that there were in many of these other places, of any impact other than humans. And by that I mean, although in the case of the continents in particular, there's been a whole series of extinctions that we know about earlier in time.

In the case of New Zealand, the only losses that we can talk about were ones that were decisively within the human period. A few others perhaps not but -- as Richard pointed out, and as he published recently in Nature -- there is evidence now that a species of rat managed to get into New Zealand at a point apparently prior to human arrival. Because of its particular habits, it may have been responsible for mediating certain kinds of extinctions or, at least, endangering certain kinds of animals. But I think what's critically important here is the notion that timing supports the idea, both negatively and positively, that humans were the leading cause. Going along with this, I would also say that, in the case of New Zealand, we have probably the best examples of kill sites. And by that I mean we not only have the occasional projectile point, we have objects made out of moa bones; we have sites that are only interpretable as human habitations, that are chockablock with moa bone that is butchered and otherwise used.

Helen James, who has worked extensively on the Hawaiian Islands -- with Storrs Olsen, with Dave Burney, with a number of other people -- has been centrally concerned with the losses in the avifauna on those islands over the past several hundred to several thousand years. And, she has shown that there was another incredible -- this is another example of the raw, gaping wound -- there were all sorts of birds occupying all sorts of guild and trophic positions that have just disappeared, leaving behind a nothingness, in some regards, that has yet to be taxically replaced, even by introductions.

One of the interesting things, however -- one of the disturbing things, in a way, for those of us who like neatness above all in patterning -- is that she thinks that some of these extinctions were protracted in time, meaning that they seem to have not gone to completion until a long time after humans arrived. Here we get into scale factors that are very difficult to assess: How big does an island have to be before it's big enough, so that you'd expect that kind of protraction? It's one of the things that needs to be investigated and understood better.

In Madagascar, we perhaps have a similar kind of thing to confront. As I've already mentioned, it seems possible that in this island, as well, the extinction schedule was protracted. Now, Madagascar is a very different place from Hawaii, as David has, I think, demonstrated beyond reasonable doubt. The center of this island -- this vast wasteland of grass -- is something that is hard to argue is exclusively anthropogenic. There's just now too much evidence to think that the Malagasy simply came in, torched everything in sight, and that's why the place looks like it does today. So it is possible, I would argue, in consistency -- to make an argument from consistency with David -- that perhaps protraction in this case was because it was just so damn hard to live in that place, just as it is today. And that people did not get into all places on the island for a considerable period of time.

For indirect impacts, we have a series of different theoretical positions that were expounded on yesterday. As I've already mentioned, Russ Graham in particular -- but I think with some sympathy from other presenters -- made a case, for at least the North American situation, that there was a strong convergence in time between how we now date those losses and certain effects, climatically speaking, of large magnitude.

The problem here is to separate the signals. Because, at that very time, it seems that people were new to the Americas, and how you parcel that out continues to be, I think, in near time. If the fact of what happened was strong enough to cause extinctions throughout the continental Americas, then why was it that these causes were not seen simultaneously, coevally, elsewhere in the world? What do losses 11,000 years ago in North America tell us about how losses were mediated a thousand years ago in Madagascar or the West Indies? That's the problem with pattern.

Norman Owen Smith, who I'm going to include in here -- not because he disbelieves that humans had something to do with it, but because he makes the interesting argument that we may not have a sufficiently complicated view of the Quaternary as we should, and that different kinds of species play very different roles. His argument here is that mammalian species of truly megafaunal size -- the really enormous guys -- created their environments -- thinking on the analogy of modern elephants -- and also created environments for other kinds of animals. So that with their disappearance, a cascade of effects might have occurred which involved the outright extinction of some of these dependent species, with an overprint, again, of humans having something to do with it.

And, finally, to probably less sympathy than Russ Graham, is the notion that perhaps one way of explaining pattern here, that recognizes the human role, that humans had to be there -- at least humans and their commensals -- that explains how these extinctions could have gone to completion with great rapidity is the argument that disease itself might have been, in certain times and places, a leading cause of extinction.

That argument has a number of severe difficulties, one being that it has an even more egregious lack of explanatory detail than some of these others, but I think it's worth thinking about. It's not offered merely as a way of trying to convert this bipolar argument into a tripolar one, but to force people to think why it is that certain of these pattern features remain hard to explain -- one being the rapidity of the loss. There are not many things in nature, other than disease, that can cause calamity on the scale necessary.

I want to end with a really important point, from my perspective. One of the things that we ended with was: Okay, there's a lot of causes out there that all seem plausible, but none seems to cover all of the phenomena that we're interested in dealing with. They all explain logically -- reasonably, perhaps -- a part of the issue, but there is no way of logically connecting them in a way that explains the whole package.

One alternative in situations like that is to say: Well, it was a multicausal situation, there were lots of things responsible, and that's the answer. I disagree. Not that it's not the ultimate answer, but this is not the way to look at it scientifically. What is most important is that we talk about causation, that we find the fact bodies that are most important to explicate pattern, and we critically test them. In that case, each and every hypothesis ought to stand, or fall, on its own merits. And if we find, at the end of the day, that none are successful, I argue that the default position is not that it's multifactorial -- I argue that the real situation is that we don't know. Consequently, we need to go back and look, once again, at the patterns to see what other things we can wring out of them. This is what separates what we did yesterday as science, because, of course, there are other explanations for Quaternary extinctions. I happen to like this one, in particular -- I'm sure you have many of your own -- but that's all they are. These are just notions. Unless there's a testing procedure, a way of evaluating in the crucible of ideas how these causes might relate to one another, it's not science.

Michael Novacek:

There may be time for one question before the discussion that addresses Ross's talk.

Paul Martin:

We are talking about islands which had big losses, catastrophic losses, when humans are entering the island environment. But there are many, many islands which didn't suffer losses at the same time. And (inaudible) about, if you take the (inaudible) Islands, where you had about nine different species of deer, one (inaudible) as a rabbit, and so on, they all became extinct about 16,000 years ago. And it was exactly then that they have the first humans entering on these islands. When you go more south, to the Philippines, and then to the islands of Southeast Asia -- the smaller (inaudible) Islands -- you have no loss at all. But, as I remarked yesterday, also, on the islands like Sulawesi, and also Flores, we have very good evidence that there was a big loss at about 700,000 years ago, when Homo erectus entered in that island environment. And then, from that time on, there must have been human occupations of those islands, and probably (inaudible) humans, islands (inaudible) recovered, and then, when Homo sapiens came later, the loss was not as big as on the other islands, which were always without humans. So I think, to solve the problem, we have to look also on the islands where there was not such a big loss, dramatic loss, as Madagascar, and to solve by that (inaudible).

Ross MacPhee:

I agree with your point, Paul. You're accusing me of being a species-ist, I think, by blaming it all on anatomically modern humans. The question is, of course, whether the effect of earlier homonids in different places might have had the same kind of effect that later homonids apparently did. That is possibly part of the pattern that needs explanation. And these exterior cases are very important for the illumination they can give us for the testing procedure. Thank you for that.

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