‘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.

That Clovis Overkill Hypothesis? How much evidence is there for it, really?

I am amazed that this Clovis as mammoth murderer to extinction idea still has traction.

I am presenting this here not to convince the reader, but to show that the popular idea of humans as mammoth “extinction machines” has another, valid, side to it.  I was not looking for this article or anything along these lines at the time I found it (a couple of months ago) – but it blew me away, that two BIG names in this area of research (Grayson and Meltzer) had such a paper out there.  In my opinion, this paper eviscerates the Overkill hypothesis.  See what you think:

See “A requiem for North American overkill” Grayson and Meltzer 2003. (Yes, the very same Meltzer who is a co-author on some of the YDB skeptical papers.) All the quotes are from that paper.

ABSTRACT
The argument that human hunters were responsible for the extinction of a wide variety of large Pleistocene mammals emerged in western Europe during the 1860s, alongside the recognition that people had coexisted with those mammals. Today, the overkill position is rejected for western Europe but lives on in Australia and North America. The survival of this hypothesis is due almost entirely to Paul Martin, the architect of the first detailed version of it. In North America, archaeologists and paleontologists whose work focuses on the late Pleistocene routinely reject Martin’s position for two prime reasons: there is virtually no evidence that supports it, and there is a remarkably broad set of evidence that strongly suggests that it is wrong. In response, Martin asserts that the overkill model predicts a lack of supporting evidence, thus turning the absence of empirical support into support for his beliefs. We suggest that this feature of the overkill position removes the hypothesis from the realm of science and places it squarely in the realm of faith. One may or may not believe in the overkill position, but one should not confuse it with a scientific hypothesis about the nature of the North American past.

They discuss island versus continental extinctions and causes.  And they argue efficiently that projecting island extinctions onto continents – which is VERY commonly done – is a completely wrong extrapolation:

The initial human colonization of island after island was followed by vertebrate extinction. That this premise is true, however, does not mean that it is relevant to continental extinctions. After all, the factors that make islands prone to vertebrate extinction — small population sizes of resident vertebrates, the lack of a ready source of conspecific colonizers, and so on — do not apply to the continental setting.

It is not enough to blame humans for mammoth and mastodon extinctions. Over 30 other species went extinct at virtually the same time – with the lack of evidence of Clovis killing them being non-existent:

How many of those genera can be shown to have been human prey during Clovis times?  The answer is two – mammoth and mastodon—(Table 2) and there are only 14 sites that securely document this relationship [39].  As has long been known [42], this is not a sampling fluke (see Fig. 1). There are more late Pleistocene occurrences of horse than there are of mammoth or mastodon, and nearly as many for camel as for mastodon, yet there are no demonstrable kill sites for horse or camel or for any of the remaining genera [30,31,34,36,37,39]. This is not for want of looking.  Given the high archaeological visibility of the remains of extinct Pleistocene mammals, and their great interest to archaeologists and Quaternary paleontologists alike, if such sites were out there, they would surely be found. Indeed, there is a strong bias in the Clovis archaeological record toward just such sites…

So, the next time you see an “artist’s rendition” like this, think about what you are reading today:

The Extinct Late Pleistocene Mammals of North America

Genus / Common name
Pampatheriuma / Southern Pampathere
Holmesina / Northern Pampathere
Glyptotherium / Simpson’s / Glyptodont
Megalonyx / Jefferson’s Ground Sloth
Eremotherium / Rusconi’s Ground Sloth
Nothrotheriops / Shasta Ground Sloth
Glossotheriumc / Harlan’s Ground Sloth
Brachyprotoma / Short-faced Skunk
Cuonb / Dhole
Tremarctos / Florida Cave Bear
Arctodus / Giant Short-faced Bear
Smilodon / Sabertooth Cat
Homotherium / Scimitar Cat
Miracinonyx / American Cheetah
Castoroides / Giant Beaver
Hydrochoerus / Holmes’s Capybara
Neochoerus / Pinckney’s Capybara
Aztlanolagus / Aztlan Rabbit
Equus / Horse
Tapirus / Tapirs
Mylohyus / Long-nosed Peccary
Platygonus / Flat-headed Peccary
Camelops / Yesterday’s Camel
Hemiauchenia / Large-headed Llama
Palaeolama / Stout-legged Llama
Navahoceros / Mountain Deer
Cervalces / Stag-Moose
Capromeryx / Diminutive Pronghorn
Tetrameryx / Shuler’s Pronghorn
Stockoceros / Stock’s Pronghorn
Saigab / Saiga
Euceratherium / Shrub Ox
Bootherium / Harlan’s Musk Ox
Mammut / American Mastodon (2)
Mammuthus / Mammoth (12)

(source: http://faculty.washington.edu/grayson/jwp02.pdf)

Only the ones in red have confirmed kill sites (number of sites).  See Clovis hunting and large mammal extinction: a critical review of the evidence (Grayson and Meltzer 2002) .  Also see How Many Elephant Kills are 14? Clovis and Mastodon Kills in Context (Surovell and Waguespack 2008).

The experts in the field don’t sign on to the idea, to their credit (but how about the rest of us and the rest of scientists?) :