‘DEAD CLADE WALKING’ – The Mammoth Connection

For those interested at all in mammoths, you probably know about them going extinct.  Some of you will also know that a very few mammoths managed to survive the immediate, main extinction, managing to make it until about 4,000 years ago before the last one bit the bullet.

In my curiosity, I frequent several blogs.  On more than one, every time the subject comes up about the mammoth population going extinct at the onset of the Younger Dryas cold period 12,800 years ago, some bloke brings up the facts of these small island populations of mammoths, the last group of which survived until more or less 4,000 years ago.   They are correct about those mammoths surviving.  But are they right about that not being an extinction event at 12,800 years ago?

There is a post-extinction-event condition called “Dead Clade Walking“. Wiki does a decent job of introducing the subject, so I will quote from them:

Dead clade walking also known as “survival without recovery” refers to a clade (group) of organisms which survived a mass extinction but never recovered in numbers, becoming extinct a few million years after the mass extinction or failed to recover in numbers and diversity.

Now, I first heard of Dead Clade Walking on the TV show Elementary, a Sherlock Holmes in modern day New York City series. I had not heard of the term when Holmes used it. He actually DID explain what it meant to Dr. Watson, and when he did, that piqued my interest.

It piqued my interest because the principle of it seemed to be exactly what happened to those small mammoth groups that survived for up to another 8,000 years – only to finally die out, anyway.

So, I looked it up.  Here is a Univ of Chicago article about it, Survivors of Mass Extinctions May Not Evolve As Winners.

“Everybody knows that some groups are so affected by mass extinctions that even though they may survive, they are but a shadow of their former selves and succumb soon after the main event,” said Karl Flessa, a professor of geosciences at the University of Arizona. A major problem with this bit of common scientific knowledge, he said, is that it had never been successfully demonstrated.

“Jablonski’s contribution is to add long-needed rigor to documenting and understanding the phenomenon,” Flessa said. . .

. . .Jablonski found post-extinction losses among survivors of 10 to 20 percent, a number lower than during the mass extinction times themselves, but significantly greater than seen during “normal” times. . .

. . .“So there’s an extra ripple of extinction in the aftermath of each of the big events, sorting out the survivors into winners and losers,” Jablonski said.

. . .“Some clades manage to stagger on for tens of millions of years,” Jablonski said.

So I seem to have assessed this correctly. It is exactly what seems to have happened to the mammoths.

Now, as those wankers keep pointing out, there was not only the one they talked about, on Wrangle Island, north of Siberia and at 71.5°N 180°W.  There also was another one other group Santa Rosa Island, one of California’s Channel Islands. Both populations are thought to have swum across from the mainland, and for some reason were not able to get back.  If either one had, we might not be talking about them being extinct.

But, for whatever reason, none of them did swim back – or at least not enough to procreate.


By staying on the islands, each was doomed. Perhaps they would have been doomed anyway.  But extinctions and islands kind of go together, in our normally Gradualistic times.  The Younger Dryas onset waS not one of those times.  Depending on who you listen to, there was either a marauding band of Killer Clovises, a proboscidean pandemic, a climate tipping point – or, as I think, a Killer Comet with their name on it.  Whatever it was, it came on suddenly (even some of the the Gradualist geologists who study it think that it happened in the geological eye blink of less than 20 years).

Archaeologists Meltzer and Grayson wrote that

That island faunas are vulnerable . . . is not surprising. As Steadman (1997) has observed, island birds are at risk in these settings because they have relatively small population sizes, are confined to tightly bounded areas of land that may undergo rapid environmental change, and may have lost—and in some cases have clearly lost—the mechanisms needed to cope with introduced pathogens, predators, and competitors. Much the same can be said for all island vertebrates, and to all of this must be added the fact that the isolated nature of islands means that there are no nearby sources of conspecific individuals to replace dwindling local populations. No wonder, as Steadman et al. (1991, p. 126) point out, “animals on oceanic islands tend to be more vulnerable to extinction or extirpation than their continental counterparts” and that, as Paulay (1994, p. 134) notes, island faunas are “among the most vulnerable in the world.”


In a 2001 scientific paper entitled “Lessons from the past: Evolutionary impacts of mass extinctions”, by Universtiy of Chicago Professor of Geophysical Sciences David Jablonski.  He wrote about Dad Clade Walking:

Clade survival is no guarantee that preextinction trends will persist or be reasserted in the postextinction setting. Each extinction has examples of clades that survived the extinction event only to fall into a marginal role or eventually disappear (dead clade walking). These include bellerophontid snails and prolecanitid ammonoids at the Permo-Triassic boundary, the brachiopod order Spiriferoida after the end-Triassic extinction, and the planktic foraminiferal Zeauvigerina lineage after the K-T event. . .

. . . My preliminary, unpublished analysis suggests that the intervals after mass extinctions tend to be significantly enriched in taxa that failed to cross the next stage boundary, relative to other intervals before the extinction event; in other words more clades that survived a mass extinction tend to dwindle or disappear shortly after the event than would be expected by chance.

[Footnotes removed…]

In other words, life is really TOUGH after an extinction event. Put a surviving species on an island and then add whatever caused the Younger Dryas biological and climatological changes to that, and the mammoths were going to be tested to the limit.  To the last ones.


Probably almost all of you who know about mammoths know that the prevailing theory about their extinction blames humans, who were new to the New World and went berserk running around North America, slaughtering them all until there were none left.  This theory is called The OverKill Theory.  The idea was originated by one Paul C. Martin [first name corrected], back in the 1960s.  The bad guys in that scenario were a people known today simply as Clovis. They are named after the amazingly crafted spear points first found in Dent, CO, but named after a more studied site outside the town of Clovis, NM.

One of the odd things about the Clovis people is that they went extinct then, too.

And one of the odd things about the Overkill Theory is that it has been challenged by Grayson and Meltzer (in 2002) and others and found very much wanting. They vetted the claimed Clovis-mammoth kill sites, and out of 76, only 12 made the grade.  Two mastodon sites also passed.

But of the other 31 species that ALSO went extinct at that time, NOT ONE Clovis kill site has ever been found.  NONE.  NADA.  NUNCA.  NEVER.

Meltzer and Grayson rip a new anal orifice in the Overkill Theory:

As the assessment we have provided here shows, however, there is no evidence that Clovis people preyed on a wide variety of now-extinct large mammals. . .

. . .Indeed, it is significant that for 33 extinct genera, and for 26 of the 28
extinct herbivores, there is no archaeological evidence at all for hunting,
and only a limited number of kill/butchering sites for the other two. . .

. . .Of the 76 localities with asserted associations between people and now extinct Pleistocene mammals, we found only 14 (12 for mammoth, 2 for
mastodon) with secure evidence linking the two in a way suggestive of predation. . .

. . .This is not to say that such hunting never occurred: we have clear evidence that proboscideans were taken by Clovis groups. It just did not occur very often. . .

. . .No statistical analysis is needed to observe that the late Pleistocene peoples of North America cannot be shown to have been preying on a full-array of now-extinct herbivores. Archaeologists have pointed this out all along (e.g., Hester, 1967; Jelinek, 1967). . .

. . .However, the issue is not whether Clovis groups were “capable” of hunting the Pleistocene fauna to extinction, but whether they actually did so, and that is an archaeological question. The archaeological answer is clear enough: they did not. This is why overkill finds so little support among those who are familiar with the empirical record of late Pleistocene archaeology and paleontology.

 [Updated – correction: Paul C. Martin’s name I wrote down as “Charles C. Martin”.  My bad. Correction made.  H/T Mark Gelbart]


14 responses to “‘DEAD CLADE WALKING’ – The Mammoth Connection

  1. Man, you are really uninformed.

    It was Paul Martin, not Charles Martin who first hypothesized about the Overkill Theory. You are so ignorant, you didn’t even get the name correct.

    Since 2002 when Grayson and Meltzer published their papers, kill sites have been found for ground sloths, glyptodonts, horses, and camels. Grayson and Meltzer have been proven wrong.

    Gary Haynes thoroughly debunked Grayson and Meltzer’s papers in several papers that he published. Many other scientists have also published papers since 2002 that support the overkill theory.

    Google it, dumbass.

    • Mark, nice attitude.

      Sorry, I got Paul C. Martin mixed up in my head with Charles C. Mann. Excuse me. I will correct it.

      And what is this “google” thing? I’ve never heard of that.

      Thanks for your leads. I will look up what you pointed at. Gary Haynes, as far as I know, is a died-in-the-wool Overkill guy, so of course he would have reacted.

      From what I see, Haynes is still going at it in public, as of last year at least, and that sure as hell tells me that the debate is still going. And if the debate is still going, then Haynes hasn’t “thoroughly debunked it”. It might be to YOUR satisfaction, but if the debate is still on, then, sorry, nothing is debunked.

      GOOD. I am GLAD there is a healthy scientific debate going on it.

      And I am entitled to side with whomever I choose to. I will dig into the rebuttals and the replies to the rebuttals. And when all is said and done, I will still think for myself, instead of being bullied. It’s my blog. I will say what I chose to. If you don’t like it, you don’t have to show up here.

      And stop with the name calling. It only makes you look like an ass.

  2. I see that that Pribilof blog is in your name. I will leave you to your blog. Enjoy it. And, man, are you a hostile mother.

  3. Also against the Overkill Theory are the people who think that climate or disease took out the megafauna. Along those lines, there is this from last year: What Killed the Great Beasts of North America?

    I don’t usually like to post magazine articles. I’d rather post journal papers. The article covers two Missouri University scientists who, in their paper last year, point out the timing of the extinctions as showing that most of the species were under duress already, before Clovis even arrived.

    I don’t agree with every interpretation in the article. I am not a climate-did-it or a disease-did-it guy, but when their arguments agree with mine about Overkill, we have common cause.

  4. One thing the article points out is that at ~14,100 ya there was a decline in megafauna populations. If something happened to stress them and take out most of them, then the Dead Clade Walking principle would apply – that they were on the brink and some second stress could have taken them out the rest of the way.

  5. I found the full journal paper that the article refers to.

    Boulanger and Lyman 2013 Northeastern North American Pleistocene megafauna chronologically overlapped minimally with Paleoindians

  6. And as a first bit about the Haynes “debunking”, Grayson and Meltzer did a reply in 2004 to Haynes and Haynes’ cohort, Fiedel.

    Basically Grayson and Meltzer took exception to the mischaracterizations in the rebuttal paper. Grayson and Meltzer admitted to no errors and stood by their 2002 paper.

    It is amazing to me how academics on one side of a debate or the other can PRETEND that the evidence of their opposite side are debunked, when in reality, the debunk supporters are in reality only showing that they take sides, and that they discount the evidence of the opposing academics.

    It is a real shame when evidence is discounted, especially by the rooters of one side or the other who are not central figures in the debate. One would THINK that the main aim is to find out ALL the evidence and let the chips fall where they may – and NOT to pretend that only evidence supporting their favored side is good, while the opposition’s evidence is somehow of a lesser quality and should be discarded. That is not very scientific. Nor honest.

    I don’t know where this debate is going to end up. But it DOES sound like Grayson and Meltzer (and papers they cite) laid down the gauntlet and are making Overkill have to prove itself much more than it had had to do in its entire existence.

    With Overkill having not one, and not TWO, but THREE competing hypotheses to explain the Late Pleistocene megafauna extinctions, the debate goes on. And Overkill has lost some standing, certainly.

    This current blog post is not taking sides, as it is written nor how it is intended. This post discusses, almost in it entirety, the fact that SOME mammoths made it out, through the big extinction “event” (whichever cause “did it”) – but that in the end, they were stressed enough that they only were able to hang on for a while. The bottleneck they went through was simply a little bit too tight.

  7. Steve; Eyes be thinking I be smelling some trolling around here. We needs to be ons our guards. I think I have figured out the timing of the mammoth, Clovis who killed who. First there was the Mammoth, then came Clovis Man and killed all the mammoths, or so they thought, the few Mammoths that were left went Rambo and picked off all the Clovis people through stealth tactics and then decided : It was a good day to die and did. Sorry for the silliness, but ————-

  8. I woke up the other day with this in my mind. It occurred to me to wonder about the second event, the one that finished off the remaining mammoths and other megafauna.

    It sounded reasonable that with severely reduced numbers the remainder would be very susceptible to disease, especially diseases that might affect reproducibility. Diseases of the females would be especially hard to survive if populations were perhaps 5% of pre-YDB.

    Total speculation, really, but Dead Clade Walking (DCW) needs a second severe event, to reduce the numbers a second time, below “extinction-ate” levels or to zero.

    This would help to explain why populations of over 30 megafauna went extinct. Currently 11,000 radiocarbon years ago is a wall for all of them. This requires a miracle of sorts. An impact of sufficient energy would account for several extinctions, but more than 30 seems a tough row to hoe. But if an impact wiped out some species and put several others into DCW class, diseases then becomes a more likely trigger for claiming the rest. And they do not need to be all the same disease (in fact, that would be a hard sell). Many papers discuss disease as a possibility, but that seems untenable by itself – if the populations were normal or near normal.

    But if the impact decimated species to a level that diseases could finish the rest off, given a bit of time, that seems to work for me.

  9. Steve; The idea of disease finishing off the last of the mammoths is a good possibility but here is another. I do some small time horse breeding, if you want to bring the female into reproductive heat you expose her to prolong daylight stimulation. This amount of daylight enters through her eye and goes to the brain which thinks it’s later in the spring than reality and releases the breeding hormones. Conversely if you reduce the available daylight exposure the brain shuts down the reproductive processes. If there was any kind of secondary event that caused a global reduction in available sunlight that would disrupt the reproduction cycles of almost all living things humans included. So the initial Saginaw impact decimates the local populations then a secondary impact either close by or large enough globally to reduce sunlight finishes off the remainder of the mega fauna. In the case of mammoths being in the elephant family the gestation period is around 2 yrs. at that rate any missed opportunities to breed could be disastrous to a imperiled species. A vet could give you a more precise description of the reproductive cycling mechanisms.

    • Jim –

      Very good. Not a bad addition and alternative at all. That certainly would be the equivalent of having a disease of the females. Something that would prevent them from breeding.

      I am quite taken with this DCW idea, how it broadens the possibilities.

      As to the impact winter idea of Bill Napier and his pals, that is one of the big skeptical things brought up on WUWT every time Anthony Watts posts a YD impact article. Someone or several people argue that an impact can’t leave dust or ash up in the atmosphere for ~1300 years. And they are right. As I normally do, when I don’t know the HOW or the WHY of something, I will stop hypothesizing and assume that we are “asking the wrong question” again – making some wrong assumption, kind of like setting up a straw man argument. In this case, the straw man is to automatically think that long cold means impact winter and only impact winter – similar to Carl Sagan’s nuclear winter, which agimarc tells us ruined Sagan’s career, because it was demonstrably WRONG.

      If we think we know all the possibilities already, then we lock into bogus thinking and closed-minded thinking, shutting us off from possible “back door” solutions. Coming up with explanations that fit uniformitarianism and SOUND good – that doesn’t necessarily MAKE them correct. But several of those are running around even now, sucking researchers into blind alleys (IMVHO).

      Well, just because it stayed cold for 1300 years:
      1. Didn’t mean that it was equally cold the entire time
      2. Didn’t necessarily mean that atmospheric dust was the reason for the extended cold
      3. Didn’t mean that we were understanding all the possibilities
      4. Didn’t mean that gradualist thinking had all the answers
      5. Didn’t mean that a volcanic ash cloud was a good analog for how it stayed old so long
      6. Didn’t mean that 1300 years was even that long of an ice period – after all that was probably the SHORTEST stadial in the Pleistocene!
      7. Didn’t mean that we understood why the OTHER stadials were longer
      8. Didn’t REALLY even mean that we understood the ice ages and what caused them
      9. Didn’t even mean that the cold is what necessarily killed off the megafauna. (I am reading a Meltzer-Holliday paper in which they argue that very point!)

      So, with so many things that are rolled into the gradualist thinking, IMO they are wrong on all of them, making a solution impossible in that direction.

      Over at WUWT, Anthony and some of the other smart guys like to point out that to build up an ice sheet, colder is NOT the way to go. WARMER causes more snowfall, as long as it is not above freezing. Think about it. How do you get snow to fall on top of 2 km of ice that is 500-1000 km from the edge of the ice sheet? How does the moisture carry that far “inland”? How do winds even deal with that? There are katabatic winds that come OFF the ice sheets, down from the top – but how do winds go UP and onto the high ice? Major parts of Antarctica right now are technically deserts – in that they have very low snowfall overall, and snow/ice evaporates faster than it snow falls, year after year. Yet, the ice mass of Antarctica is growing at the moment; it goes through growing and shrinking stages. But how does it get built up so much in the first place, if too much cold is a negative?

      Also, they point out that in ice ages the overall Earth climate is dryer, with dust storms being common outside the ice areas. The big reason for that is DEcreased oceanic and continental evaporation around the world. That is what climate people say.

      Now, the Younger Dryas WAS a stadial – a time when ice WAS building up. So there had to be less evaporation, by that standard.

      But: For the most part, the mammoths didn’t even make it INTO the Younger Dryas, only just up to the starting point. They did not (most of them) pass GO, and did not get to collect $200. Anyone thinking that climate itself instantly killed off the megafauna needs to have a brain transplant. Specifically because of the argument that Meltzer and Holliday make – that the mammoths and mastodons lived through far worse ice ages, so why did the short one take them out? The answer is that that is the wrong question. If the great majority didn’t live long after the ONSET of the Younger Dryas, then talking about the length of the Younger Dryas is a moot point.

      But if Dead Clade Walking is allowed into the discussion, THEN the length of the YD stadial may mean something. OR PERHAPS NOT!

      Impacts the size of Tunguska are currently said to occur about once every 200 years or so. Tunguska took out about 2,000 square kilometers of forest. If a second impactor/airburst was like Tunguska, then would that be enough to take out the rest of the mammoths? If they were all unlucky enough to be on an island smaller than 2,000 sq km, then yes – but only IF the impactor happen to choose THAT island. And there is no real reason to think that that low-odds target would get hit.

      A widespread event of some sort seems much more likely – something like dust blocking off sunlight.

      HOWEVER, as the commenters at WUWT pointed out, no dust can stay up more than a few years. With the longevity of pachyderms, a few years of high altitude dust should not have bottlenecked them out of existence. Only a very long such event could do that – but that does not seem to be possible. Not from what I’ve read over the years.

      I am intrigued at the direction our thinking is going in right now. Particulars may or may not preclude a dust event or “darkness contraceptives” (or any of the other suggested possibles). But if ANY of those suggested extinction mechanisms happened after an initial population bottleneck, then any one of them would be more likely to provide the coup de grace. As a “first decimator”, I don’t see any but an impact being able to do that over an entire continent.

      And, I guess, one of those might even BE the ice – if and only if the first event decimated the populations first, creating a bottleneck of the 2nd order. With a 1st order bottleneck being a complete extinction in one step, with zero making it through the bottleneck.

      • Steve; I just read your last post about the commenters at WUWT saying that the airborne debris comes down too fast to have any impact. I can take a mare in the dead of winter, she hasn’t cycled in 2 months, and put her under lights for 2 weeks and she’s in raging heat. Conversely if I restrict her access to light I can shut down her reproductive abilities in about 2 weeks. The same is true for plants any reduction from the norm on light exposure will start shutting them down. No plants no mega fauna etc. The whole house of cards comes down. Plants shut down in autumn not because of the cold but because of the lack of light exposure. Animals shut down for the same reason. Between lack of reproduction ability and the lack of food supplies the already weakened Clade collapses. Don’t forget this was not just a North American event, It had global ramifications. Possible other impacts, more than likely water targets for lack of “cratering”, Though basins globally may be indicative of Michigan style impacts. The second Sudbury impact appears to have taken off the NE end of the original crater. I can’t imagine the dating being off by that much but I can’t see the tracking being that close over a couple of billion yrs. The only possible explanation I can come up with is that a LONG orbit comet was able to meet up with earth again at the exact same time and place and break up some more at that exact same time and place and that is a LONG LONG LONG LONG shot in the dark!

        • Jim –

          I am agreeing with you about the light>raging heat thing. That is a very cool thing to know. And as soon as the light gets above that threshold the females are going to go into heat again, right? 2 weeks later? Even if it takes a year or three? (Some horny studs on your hands by that point?) How long before an entire generation doesn’t reproduce?

          The 2nd Sudbury crater – what do you think? Maybe one or two more “LONG LONG LONG”s to that shot in the dark? Not gonna happen. And that is my same point about the MI Basin and Saginaw AND Sudbury – they line up that well and are NOT in the same crater chain? We can only put it out there and say that it seems to make sense or it doesn’t…

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