From: rsquires@cyclops.eece.unm.edu (Roger Squires)
Subject: Re: Pliestocene extinctions
Date: Mon, 31 Aug 92 23:58:49 GMT
Organization: University of New Mexico, Albuquerque

>Bear Giles writes...
>	Humans enter Europe and virtually all other large predators
>	are eliminated.  Saber-tooth tigers, extinct.  Cave bears, extinct.
>Scott I. Chase writes:
>	I'm not convinced.  In the Americas, Saber-tooth tigers and other
>	large carnivores underwent a rather sudden extinction around
>	something like 50K years ago.  Meanwhile, the earliest human remains
>	are roughly 25K years old.  I have been able to verify the human
>	data (it's "Los Angeles Man") but not the timing of the extinction. 
>	But if my numbers are correct, then these animals died out on their
>	own, with no assist from us, at least on this continent.
>	Anybody out there with some real knowledge?

	Well, I'm not a scientist, but this topic was raised on talk.origins
	some time ago, and here is what I posted back then.  It has
	various references Mr. Chase can look at.  I deleted the
	newsgroups talk.religion.newage and sci.physics as they seemed
	irrelevant to the discussion.

Subject: Man the Exterminator (Was Re: Cold-adaptation of mammoth?)
Organization: University of New Mexico, Albuquerque

This post deals with human predation of mammoths and other creatures
in pre-historic times.  My sources are listed at the bottom on the post.
I was careful about sources, only using ones from 1984 and better.
My thanks to Mr. Holden for his response to my post, as otherwise I would
not have spent an enjoyable evening reading about dinosaurs and mammoths
(and enjoying a can of Dinosaur Vegetable Soup, no less!).  There is no way
I can deal with all the issues Mr. Holden raised in his response, like diet,
climate, etc.  All I wish to argue is that man was an important factor
in the extinction of large herbivores of the late Pleistocene.

Hopefully we can avoid the name-calling that is common in other threads.
I *will* *not* participate in shouting matches with anyone on the net -
I will terminate the conversation if I see a tendency towards this behavior.
With that out of the way, let us proceed...


In article <2710@fedfil.UUCP> news@fedfil.UUCP (news) writes:
>In article <_tjj-mg@lynx.unm.edu>, rsquires@cyclops.eece.unm.edu (Roger Squires) writes:
> 
>> Could I ask what your sources indicate is the reason(s) the Mammoth became
>> extinct?
>
>[..]  Velikovsky's
>"Earth in Upheaval" gives the best available explaination of mammoth
>extinctions.
>

I'm sorry, I have not read Velikovsky.  Is the scenario that of approach
by rogue planets/stars?  Does this account for both the Cretaceous and
Pleistocene extinctions?

>Nor is there any real evidence that man caused these great extinctions,
>both in America and in the arctic circle.  Aside from the fact that
>modern military vehicles and automatic weapons would have been needed, I
>am not even aware of any evidence of human settlement of the Liakhovs or of
>Novo-Sibirsk.
>

Well, in my post I take precisely the opposite viewpoint...
Firstly, I will start by quoting from abstracts of the papers listed in
reference [1].  This reference is a bibliography of papers on mass
extinction.  Firstly from the Research Review written by the compiler:
	Man as a Cause of Extinctions
	...There is clear evidence that when he first populates an area,
	particularly an island, he frequently causes the extinction of
	a significant number of species by hunting, [& other means]...
	...There is some evidence that his arrival on the North American
	continent may have resulted in the demise of several species
	of large mammals, most notably the mastodon.

Twelve papers are listed under this heading. Three deal with island
extinctions by man;
Eight of the other papers listed deal with human predation of large
herbivores, specifically mastodons and South American ground sloths.
I wish I had a scanner!  Two papers document mastodon butchery from 
recently excavated skeletons and experiments with primitive tools
by North American Paleo-Indians[2,3].  An abstract from another paper[4]:
	Mastodons lived successfully in North America for 15 million
	years before they disappeared about 10,000 years ago.  Since 
	man arrived on the continent about the same time, some 
	scientists have suggested that hunting by paleoindians
	caused the mastodon's demise.  Large mammals like the mastodon
	would be particularly susceptible to hunting pressure because
	they don't become sexually mature until about 10 years of age
	and have a gestation period of 2 years.  Extinction could
	have come in 100-1000 years.
Other papers note that there could have been a synergistic effect
between human predation and that of other large carnivores, that the
"overkill hypothesis is the most plausible" one for the extermination
of the Giant Armadillo, etc..

The overall tenor of these papers is that the extermination of
these large herbivores is a result of a combination of climate changes
and man.  The question is, which was more important?  The next long
quote is from [5], which is a volume dealing with Megaherbivores.
This volume deals specifically with the ecology of large modern
herbivores (rhino, giraffe, elephant, hippo), but it has a chapter
on the Pleistocene extinctions, which I will quote from at length:

	[Chapter 15, Late Pleistocene extinctions]
	...The extinctions occurred during a time of rapid climatic
	change, with associated transformations in habitat conditions.
	Another important event took place at about the same time: the
	entry of humans into the Americas, following their expansion
	through the furthest corners of the Old World.
	...In the following analysis I focus specifically on large 
	mammalian herbivores, since it is generally accepted that
	extinctions of carnivores and of large scavenging birds were
	related to their dependence upon the herbivores as a food source.
	It is the herbivores that are likely to be the most responsive
	to changing habitats; and it is also such species that were
	the prime targets as prey for the expanding human population.

	[next follows a recounting of the pattern of extinctions]
	The wave of extinctions was thus especially severe in North
	and South America, ... In those continents suffering severe
	extinctions, the incidence of generic extinction was positively
	correlated with body size.

	Climatic change
	The paleontological record shows that episodes of extinction
	commonly coincide with periods of rapid climatic shift.
	[a long discussion of global climate changes, with the
	 upshot being:]
	The extreme habitat transformations that occurred in the far
	north are sufficient to account for the extinctions of
	grazing ungulates in this region.  However, the almost synchronous
	disappearance of a variety of large herbivore genera at lower
	latitudes in NA...and SA, remains unexplained. ... No explanations
	have been advanced as to why habitat changes were especially
	inimical to the survival of megaherbivores.
	... Thus hypotheses based on climatic change fail to explain either 
	the geographic distribution of extinctions, or the fact that
	likelihood of extinction increased with body size among herbivores.

	Human predation
	The earliest evidence of human hunting of mammoths dates from
	around 70000 years BP.  Specialized hunting of mammoths is
	associated with narrow flint speartips capable of penetrating
	the thick hide. ... In Russia and Siberia, there is abundant 
	evidence of humans hunting mammoths, horses, bison and reindeer,
	and in some places wooly rhinos.  Some encampments in Siberia
	have houses constructed from the accumulation of mammoth bones.
	[there are pictures of these houses in [6]]
	[this next paragraph about spear-heads is *great*!]
	...At about 11500 BP, the characteristic stone spear-heads
	of the Clovis culture became abundant throughout the conterminous
	United States.  After 11000 BP, the Clovis points were abruptly
	replaced by the somewhat different stone points of the Folsom 
	culture.  While Clovis points commonly accompany mammoth remains,	
	Folsom points are associated only with bison and smaller species.
	There is also evidence of the hunting of mastodonts during
	Clovis times.  In the conterminous United States, the most precise
	terminal dates for extinct species, from Racholabrea, CA, cluster
	between 11200 and 10800 years BP, i.e. at the end of the Clovis
	period.

	[evidence for hunting in SA, and more recent extinctions correlated
	to human presence in Madagascar and New Zealand]

	[problems with the "human overkill" theory put forward by Martin]

	The role of megaherbivores
	Human predation was undoubtedly a major factor in the extinctions
	of megaherbivores.  There is abundant evidence of the importance
	of mammoth, ... and wooly rhino, as a prey of humans in northern
	Eurasia. [mammoths, mastodons, gomphotheres, as well]
	...Very large animals that evolved with contact with humans would
	be especially vulnerable to this novel predator.

	[much more good stuff I better not quote]

	In summary, the scenario that I propose follows this sequence:
	1)  Sustained human predation causes naive populations of
	megaherbivores to decline as harvests exceed replacement potentials.
	2)  The climatic and habitat changes associated with global warming
	compress megaherbivore distributions and places these species
	under increased food stress, making them more vulnerable to being
	hunted to extinction.
	3)  The disturbing influence of megaherbivores on vegatation is
	thereby removed, leading to trends towards dominance by late
	successional plant species and more uniform zonal habitats.
	4)  Vegetation becomes less favorable for smaller herbivores, 
	inducing population declines by these species, with predation
	by humans deprived of megaherbivores probably promoting their
	slide towards extinction; a crucial factor was perhaps the
	inability of the island population remnants to follow shifting
	vegetation zones.
	5)  Mammalian carnivores and scavenging birds decline due to the 
	disappearance of much of their food resource.
	6)  Birds and other small vertebrate species dependent upon
	the disturbed habitats created by megaherbivores disappear.

	...The one certain factor distinguishing the terminal Pleistocene
	from the end of the previous glacial periods was the presence
	of humans as sophisticated hunters.  Human hunting must inevitably
	have had a great impact on the populations of very large species,
	which had been largely free of predation by carnivores except
	on juveniles. The elimination of the impact of megaherbivores
	must inevitably have caused habitat changes, ... that may
	have played an important role in the extinctions of lesser
	herbivores...In other words, if it had not been for human presence,
	most of these species would have survived into the Holocene.
	Thus I conclude that human predation on megaherbivores was the
	necessary and sufficient cause of the wider spread of extinctions
	among large mammals at the end of the Pleistocene.

	Summary
	...The demise of megaherbivore populations through their inability
	to sustain organized human predation resulted in the removal of
	their positive influence on vegetation diversity and nutritional
	content.  This precipitated cascading effects on other species
	dependent upon disturbed habitats.  Human predation on megaherbivores
	was thus the prime factor in the late Pleistocene extinctions,
	with the climatic changes and their effects on vegetation aiding
	the timing of the extinctions.

Now, how will Mr. Holden respond to the above arguments?  Good question.
My reference [1] only lists one paper that suggests an "external"
stellar hypothesis for mastodon extinctions:
"Mulling over Mastodon Extinction", Science News, V130 11-22-1986
in which ozone depletion via a supernova could have killed off
plants needed by the mastodon.  I have a feeling that his response
will attempt to circumvent the sources I have cited by focusing
on causes of the Ice Age itself rather than attempting to respond
to the argument they present directly.  The geology book I have (1978, old!!)
gives two reasons for the occurrence of ice ages: a long term factor
due to 
	1) Increasing continentality
	2) continental drift
which lowered temperatures over the last 50-60 million years, and
a short term factor called the Orbital Hypothesis, due to the earth's
rotation around the sun.  Can anyone comment on recent theories of
how the Ice Ages came about?  The section in [1] on the Cretaceous
extinctions does mention periodicities that may be due to comet showers
or a planet X.  Is the Nemesis theory dead?


[1]	Death of the Dinosaurs and other mass extinctions
	Oryx Science Bibliographies
	Oryx Press, 1987
	This one has quite a few papers covering the mass extinctions
	of the cretaceous, by comet, or by volcanoes, a nemesis star,
	planet X, etc.  What follows are a few of the papers listed in
	this book.  I have not read these papers, only the abstracts.
[2]	"Mastodon butchery by north american paleo-indians"
	Nature, V308, 3-15-1984
[3]	"What drove mastodon off the earth?", new scientist, V101, 3-29-1984
[4]	"Bloody End for Mastodons?", Science News, V124, 11-83

[5]	Megaherbivores, The influence of very large body size on ecology
	R. Norman Owen-Smith
	Cambridge U. Press, 1988

[6]	On the track of the Ice Age Mammals
	Antony J. Sutcliffe
	British Museum, 1985

>Ted Holden

Roger Squires
rsquires@cyclops.eece.unm.edu
Newsgroups: talk.religion.misc,alt.atheism