Pleistocene Tornadoes and Windthrow Ecology

February 18, 2017

Unstable weather conditions spawn outbreaks of tornadoes.  Cold fronts collide with warm air causing the chilled air from the upper layer of the atmosphere to plummet, creating swirling winds of great destructive force.  Tornado intensity is classified according to the Fujita scale or F scale for short.  Tornado wind speeds range from less than 73 mph (an F0 tornado) to estimated wind speeds of 261 mph-318 mph (an F5 tornado).  One of the largest outbreaks of tornadoes in recorded history occurred in early April, 1936.  At least 12 tornadoes struck the south from Tupelo, Mississippi to Anderson, South Carolina.  A tornado from this system that hit Tupelo left a path of destruction 15 miles long.  Another tornado from this storm traveled 50 miles from Alabama to Tennessee.  Two tornadoes merged in Gainesville, Georgia, killing 200 people in a factory and a department store.  Overall, this storm system wiped out 454 human lives.

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F5 tornado in Oklahoma.  I hypothesize storms and tornadoes were much more frequent and severe during some Pleistocene climate phases than they are today, but they may have been less severe during others.

I hypothesize tornado frequency and intensity was greater during some climatic phases of the Pleistocene than it is today.  As far as I can determine, no scientist has ever published a study of paleotornado frequency, probably because there just isn’t any method to collect data about past transient phenomena. Incidentally, I invented the term, paleotornado, in case a scientist figures how to study them.  My hypothesis is conjecture, but I am confident it is correct.  I base it on 3 lines of indirect evidence.

a) Data from ice cores in Greenland shows average annual temperatures fluctuated dramatically during Ice Ages.  There was an alternating cycle of sudden warm spikes in temperature that melted ice dams which in turn released glacial meltwater and icebergs into the ocean, shutting down the gulf stream.  This caused an equally sudden reversal in temperatures.   By comparison today’s climate is relatively stable, yet even with a stable climate, tornadoes form with regularity. When climate changed more rapidly in the past, it seems logical to assume there was an increased frequency of colliding warm and cold weather fronts.  I believe the middle south was an Ice Age tornado alley.  Temperatures in south Florida and the Gulf Coast were warmer than they are today because oceanic circulation ceased and warm water stayed in the Caribbean, but the upper south was only a few hundred miles from the Laurentide Ice Sheet that covered Canada and New England.  Cold fronts blowing off the Ice Sheet met warm fronts originating from the Gulf of Mexico in what must have been an exceptionally stormy transition zone.

b) An unusually cold phase of climate, known as The Little Ice Age, occurred between 1310-1850.  Anecdotal historical references suggest storms were more frequent and intense during this time period.  In Europe several storms killed hundreds of thousands of people.  The Little Ice Age is a tiny blip compared to the climate fluctuations of the Wisconsinian Ice Age as recorded from Greenland ice core data.

c) Geological evidence suggests river flooding in southeastern North America was much more severe during the early Holocene (11,000 BP-6,000 BP).  These massive floods caused supermeandering river patterns.  An increase in river flooding indicates an increase in storm activity and hence tornadoes.

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Windthrows open up the forest canopy and dramatically change the local ecology.

Tornadoes, thunderstorm downbursts, and hurricanes have a profound impact on forest ecosystems and may be a primary driver of evolutionary relationships.  Areas of forest felled by wind are known as windthrows among ecologists.  Tornadoes can travel for many miles, and they leave long scars of fallen and splintered trees that can be seen in satellite and aerial photographs.  These long windthrows create gaps in the canopy where shade intolerant species can thrive.  In southeastern North America canopy gap formation is beneficial for oak, pine, persimmon, sumac, grapevine, blackberry, composites, and grasses.  Windthrows can become tangles of luxuriant vegetation that provide forage and cover for forest edge species such as whitetail deer, cottontail rabbits, and ruffed grouse.  Fallen rotting timber attracts beetles, food for woodpeckers and other birds.  The extinct ivory-billed woodpecker formerly relied on vast tracts of timber with freshly created windthrows from annual storms.  Unlike extant woodpeckers, they depended upon early colonizing, shallow burrowing beetles.  Snakes and lizards lay their eggs in rotting timber.  Bears tear up these logs, looking for beetle larva, termites, and reptile eggs.  The pits created when trees are uprooted fill with water following heavy rains, and they serve as breeding pools for amphibians.  Most of the organisms that live in southeastern North America evolved to thrive in canopy gaps resulting from wind storms.  Plants able to resprout after sustaining wind damage have a competitive advantage over those species easily uprooted and killed, and the animals that browse and can digest those plants also enjoy a competitive advantage.

One study estimated wind felled 20 square miles of forest per year in pre-settlement forests of Wisconsin.  They also estimated the recovery time for northern hardwood-hemlock forests to erase the windthrow scar is 1210 years.  The recovery time in southeastern forests is probably quicker due to the longer growing season. A tornado can leave a long-lasting impact on the landscape, and wind may be a critical element, along with megafauna foraging and fire, that may explain why Ice Age environments were so much more open than they were in late Holocene environments.

Reference:

Canham, Charles; and Orie Loucks

“Catastrophic Windthrow in the Presettlement Forests of Wisconsin”

Ecology 1988

U.S. Government Will Allow Religious Nuts to Bury a 1 of a Kind Scientific Specimen

February 13, 2017

Democrats like to paint Republicans as being anti-science and of course this is true.  Republicans dispute scientific facts about everything from the harmful effects of pollution to the fundamental basis of biological science.  But when it is politically expedient, democrats can be just as anti-science.  On September 28, 2016 democrats caved-in to religious nuts who want to bury an extremely rare specimen where it will be lost forever to science.  The specimen is known as Kennewick man, first discovered 20 years ago.  It’s a nearly complete skeleton of a man who lived 9,000 years BP.  Skeletal remains of humans from this age in North America are so rare that only a few have ever been discovered.  The Army Corps of Engineers was going to let Native American tribes bury this precious specimen shortly after its discovery, but some scientists banded together and sued for the right to study it.  They won in court and luckily we now have increased our knowledge about the life of early archaic man in the Pacific northwest.  In 2015 a genetic study of this specimen determined Kennewick man shared a common ancestry with modern Native-Americans.  Unfortunately, this gave new legal momentum to the religious nuts who want to perform a ceremonial burial with the specimen, even though the study did not show any direct relationship with the tribes that inhabit the region today.  An amendment introduced by a democratic congresswoman was attached to a bill signed by then President Obama that will let these idiotic Indians throw away any more potential scientific knowledge we can learn about Kennewick man.  Future advancements in science could give us the opportunity to glean further knowledge from the specimen, but alas, unless there is another successful lawsuit, this rare specimen will be lost.  And it’s all because of the unnecessary deference given to stupid superstitions.

This clay facial reconstruction of Kennewick Man or "the Ancient One" was carefully sculpted around the morphological features of his skull, and lends a deeper understanding of what he may have looked like nearly 9,000 years ago. The remains will be repatriated to Columbia Basin tribes for traditional burial under legislation passed by Congress. Photo: Brittney Tatchell, Smithsonian Institution

The government is going to let ignorant Native-Americans bury this 9000 year old skull. A nearly 1 of a kind scientific specimen will be lost to science forever.

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I didn’t realize that Obama and the democrats were just as anti-science as the republicans.

In my opinion all religion is brainwashing for simple-minded people, and scientists know this, though they are often reluctant to say so.  If this dispute involved Christian fundamentalists, many scientists would be loudly protesting this amendment.  I’m sure they would call them “bible thumpers.”  But they seem unusually quiet about this because they are afraid of being called racist or politically incorrect for getting in a conflict with an indigenous belief system.  Well, I won’t be silenced.  I have no tolerance for ignorant beliefs no matter what group spouts them.  These Native-Americans are pushing their religion on us, and I think it is an outrage.  This specimen doesn’t belong to them.  They did not personally know Kennewick man.  None of their great-great-great-great-great grandparents knew Kennewick man.  In fact the ancestors of some of these tribes may have even fed upon Kennewick man’s kin.  (See: https://markgelbart.wordpress.com/2012/10/24/native-american-cannibalism-and-dog-eating/ ) Their claim on this specimen is based on phony political correctness. They can’t demonstrate to which tribe Kennewick man belonged, probably because none of the tribes existed yet when he lived.  So all the 5 tribes of the Pacific northwest (Umatilla, Nez Pierce, Colville, Yakama, and Wanapum) are going to share the burial ceremony, and the specimen is going to be buried in a secret location to prevent disinterment. How ridiculous.  What politically correct bullshit.  When Europeans discover thousand year old human specimens in Europe, no group ever comes forward to claim they have the right to the remains because they are relatives.  Human remains are not sacred…they are just bones.

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Native Americans on their way to bury scientific knowledge.

After I die I do not want to be cremated.  I want to be buried, so there is a chance my remains could be discovered by scientists 30,000 years in the future.  They can study or do whatever they want with my skeleton, and I’m pretty sure I won’t care.

The Most Cataclysmic Ice Age Floods

February 11, 2017

Climate patterns were different during Ice Ages.  The Rocky Mountain region of North America is mostly arid today, but more precipitation and lower rates of evapotranspiration led to the formation of vast lakes during cooler climate phases.  Most of these lakes gradually disappeared in non-dramatic fashion after the climate became warmer and drier.  Evaporation changed the former sites of these freshwater lakes into empty basins, salt plains, and much smaller salt lakes.  But the demise of Glacial Lake Missoula caused a spectacular flood, perhaps the largest deluge in earth’s history.

A southern lobe of the Cordilleran Ice Sheet blocked the flow of the Clark Fork River near the border of present day Idaho and Montana, creating a glacial lake as big as Lake Erie and Lake Ontario combined.  At times it was almost 2000 feet deep, though it periodically lowered and partially drained.  The ice dam itself was an astonishing 2000 feet high.  The warm climate phase that marked the end of the Ice Age beginning about 15,000 years ago melted the ice dam, and the tremendous volume of water in Lake Missoula burst across Idaho and eastern and central Washington, finally emptying through the Columbia River valley into the Pacific Ocean near the present day town of Astoria, Oregon.  This massive flood created a landscape known as the “channeled scablands.”  The geological formations that serve as evidence of this cataclysm are impressive and picturesque.

Areal Scenario Map of the Ice Age Floods - Click to View Larger Image

The largest floods in the history of North America occurred in the Pacific northwest following the end of Ice Ages.

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These geological landforms were caused by post Ice Age floods.

Below is a link to many more photos of these formations.

http://hugefloods.com/Scablands.html

The flood carried large boulders encased in icebergs.  These “erratics” can be found throughout the channeled scablands.  There are dry falls–350 foot tall hills under where 300 feet of Lake Missoula water formerly flowed in what were temporary waterfalls.  Huge ripple marks can be seen on Camas Prairie.  Other amazing formations are the kolk potholes where swirling eddies gouged out deep troughs.  Strandlines and lake deposits visible on the sides of mountains are evidence the dissolution of glacial lakes occurred repeatedly in this region–perhaps more than 34 times during the Pleistocene.

The scouring of these intermittent Ice Age floods eroded most of the topsoil in this region and much of the scabland is unsuitable for crops.  But there are some exceptions.  The tops of some hills were above the flood and still have enough soil for growing crops, and some soil eroded from mountains into some valleys where crops can also be grown.  But for the most part agricultural activity here is limited to livestock grazing.

Humans began colonizing North America about the same time this cataclysmic flood occurred. Any people in the path of the deluge perished.  Members of the sparse population living on the edge of the flood witnessed an unusual, awe-inspiring event, a story they likely told their children and grandchildren.  It may be the origin of ancient flood myths found in Native American lore.  Flood myths are known in cultures worldwide and probably are based on inherited memories of local floods that occurred at the end of the Ice Age when glaciers melted and sea level rose rapidly.

Reference:

Smith, Larry

“Repeated Sedimentation and Expanse of Glacial Lake Missoula Sediments: A Lake Level History of Garden Gulch, Mountain, USA”

Quaternary Science Review January 2017

The Unknown Mating Habits of Saber-toothed Cats (Smilodon fatalis)

February 5, 2017

The average male saber-toothed cat was only slightly larger in overall body size than a female saber-tooth, but they had significantly larger mandibles and upper canines (the fangs).  This is in contrast to most species of cats today.  Most male cats and especially lions are much larger than the average female of their species.  The mating habits of Smilodon are completely unknown, and we can only speculate about them based on the knowledge that they differed in size above the neck, but not much elsewhere aside from the sexual organs.

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Smilodon had low sexual dimorphism in body size, but males had significantly larger mandibles and upper canines.  Did males share their larger kills with females as way to attract them?

I believe saber-tooth mating habits may have been notably different from those of all extant species of cats.  The saber-toothed and the scimitar-toothed cats ( Dinobastis or Homotherium ) belonged to an extinct subfamily of cats known as the Machairodontinae.  The Machariodontinae diverged from all other cats an estimated 13 million years ago, very early in cat evolution, and they have no close living relatives today.  They were more closely related to other carnivores than modern day species of cats are.  Perhaps they lived in matriarchal societies like the spotted hyena ( Crocuta crocuta ), another species that shows low sexual dimorphism (the females are actually slightly larger than the males).  Or maybe, as in the wolf ( Canis lupus only the dominant male and female of the pack were allowed to mate.  However, scientists disagree over whether saber-toothed cats were social or solitary animals.

Some scientists argue evidence from the La Brea Tar Pits of severely injured saber-tooths that survived traumatic debilitating injuries suggests they must have lived in groups.  But others believe that even a severely injured saber-tooth could have lived for a long time by scavenging.  A saber-tooth in a bad mood due to pain could have easily intimidated smaller predators from their kills. Moreover, their small braincases also indicates they didn’t live in groups.  I suspect they were solitary cats, though mothers probably hunted cooperatively with nearly grown cubs when she was training them how to hunt.

The males were able to bring down larger prey than the females because their bites, aided by the larger jaws and fangs, were deadlier.  Perhaps this was an element of their mating system.  Females that came to scavenge the male-killed prey were tolerated by the males, and the heavy meal caused them to go into instant heat.  Maybe females followed the most successful hunting males with the frequent nutritious meals triggering more frequent ovulation.

I’ve always been fascinated over how recently this strange exotic animal became extinct–only ~10,000 years ago.    It’s frustrating not to be able to know more about how it lived.  Relying on guesswork is just not as satisfying as knowing.

References:

Christiansen, P.; and John Harris

“Variation in Craniomandibular Morphology and Sexual Dimorphism in Pantherines and the Sabercat Smilodon fatalis

Plos One Oct 2012

Meachen-Samuels; J.A.; W.J. Binder

“Sexual Dimorphism and Ontogenetic Growth in the American Lion and Sabertoothed Cat from Rancho La Brea”

Journal of Zoology 2010

Panthera atrox: the 1007 Pound Giant Lion

January 31, 2017

An extinct species of lion ( Panthera atrox ), similar but larger than the extant African lion ( P. leo ), occupied open habitat in North America from California to South Carolina and Florida for over 300,000 years.  The American lion evolved from the also extinct Eurasian cave lion ( P. spelea ) when the ice sheet that covered Canada isolated the 2 populations from each other. The 2 species never re-connected during interglacials because extensive spruce forests, an unfavorable habitat for lions, grew between them.  Fossil evidence of large carnivores is relatively uncommon because their populations are smaller than those of their prey. But there are 2 fossil sites that preserved a considerable number of carnivores due to unusual circumstances, and scientists were able to collect enough lion specimens from them to study and compare the anatomy of the species as a whole.  The 2 sites are Natural Trap Cave in Wyoming and the Rancho La Brea Tar Pits in California. Scientists estimated average body size and the results were astounding.

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Hercules is the world’s largest cat. It is a 922 pound lion x tiger hybrid that lives at the Myrtle Beach Safari Preserve in South Carolina.  It is smaller than the estimated size of the largest known fossil specimen of North American lion, an extinct species that formerly lived coast to coast.

The largest male Panthera atrox specimen came from an animal that was estimated to weigh 1007 pounds, though the average male weighed 544 pounds.  The largest female American lion was estimated to weight 577 pounds, while the average was 390 pounds.  By contrast the average extant African male lion weighs 392 pounds.  This means the average female American lion was about the size of the average male African lion.  The large difference in size between the sexes, known as sexual dimorphism, suggests American lions lived in social prides like their African cousins.  An 1000 thousand pound lion would be too large and slow to hunt successfully enough to sustain its bulk, but instead relied on the smaller more agile females to secure all the bison, horses, and camels he required.  A large pride could probably even take down a full grown mammoth.

The large size of the males helped them fend off other male lions that wished to usurp their mating rights and kill their offspring.  The enormous powerful males could also aid in protecting the pride’s kills from competing carnivores such as bears, saber-tooth cats, and dire wolves.  American lions had longer legs and bigger braincases than African lions, so they were faster runners and smarter as well.  P. atrox really was a king of the beasts.

Reference:

Wheeler, H.T; and G.T. Jefferson

Panthera atrox: Body Proportions, Size, Sexual Dimorphism, and Behavior of the Cursorial Lion of the North American Plains.”

In Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne edited by L.B. Albright III

Museum of Northern Arizona Bulletin 65

Mammoths and Mastodons were Year Round Residents of the Ohio River Valley during the Late Pleistocene

January 27, 2017

The bones and teeth of an extinct animal provide scientists with information about the life history of that particular individual.  Recently, 2 scientists analyzed the chemistry of 8 mammoth ( Mammuthus columbi ) and 4 mastodon ( Mammut americana ) teeth collected from Hamilton County, Ohio and Bullitt and Gallatin Counties, Kentucky–in other words, the Cincinnati area.  They determined 11 of these animals spent their entire lives in what was to become the Cincinnati area.  They also learned 7 of the mammoths ate different plant foods than the mastodons, but the diet from 1 individual mammoth did overlap with mastodon diets.

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Hamilton County, Ohio

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Mammoths and Mastodons lived year round in the Ohio River Valley.  They were 2 completely different species of proboscidean.

Scientists are able to determine where an animal lived during its lifetime by measuring the ratio of strontium and strontium isotopes in their teeth.  Strontium leaches from local bedrock into the water supply, and animals absorb the strontium into their bones when they drink.  Different geographical regions exhibit different ratios of strontium isotopes, so it’s possible to figure out where an animal spent time during its life.  A previous study of mastodon and mammoth teeth collected from Florida determined mastodons there migrated back and forth from central Florida to central Georgia, while Florida mammoths did not migrate.  But this study suggests most of the mastodons that lived in the Ohio River valley did not migrate.  However, there were exceptions.  The strontium ratio from 1 specimen indicated this individual wandered north from either north Georgia or southern Tennessee to the Ohio River valley.  The authors of this study estimated this could have been accomplished in as little as 5 days based on how fast modern elephants can travel.

The bone chemistry tells us mammoths mostly ate grass, while mastodons ate plants that grew in forested environments.  But again there was 1 exception–1 mammoth that fed upon forest vegetation.  During the Last Glacial Maximum much of this region was a cool arid steppe environment.  After the nearby ice sheet retreated, the steppe was transformed into an open spruce parkland, then eventually an oak and hardwood dominated forest.  This mammoth apparently adapted to the latter changes.

Mammoths and mastodons had no need to migrate away from the Ohio River.  The rich floodplain habitat and numerous mineral licks provided enough nutrition to support year round populations of both.

Reference:

Baumann, Eric; and Brook Crowley

“Stable Isotopes Reveal Ecological Differences among now Extinct Proboscideans from the Cincinnati Region, USA”

Boreas 2015

Donald Grayson’s Disingenous Case Against Overkill

January 23, 2017

I almost chose not to read Donald Grayson’s most recent book, Giant Sloths and Sabertooth Cats: Extinct Mammals and the Archaeology of the Ice Age Great Basin.  Grayson is a long time skeptic of the hypothesis that man overhunted Pleistocene megafauna to extinction, and he has authored and co-authored a number of papers explaining his position.  In my opinion overhunting by man is the only explanation for the extinction of Pleistocene megafauna that makes sense.  I’ve read his papers and consider his arguments highly illogical and unfair.  But I did purchase his book because I try to absorb all the knowledge I can about my favorite subject–the late Pleistocene ecology of North America.  I don’t have to agree with an author about everything to enjoy their work.  I saw his chapter on extinction was short, just a small portion of the book, and I assumed he would simply rehash his tired old case against overkill.  However, I was shocked at the way he misrepresented the results of a paleoecological study.  He implies the results of this study support climate change models of Pleistocene megafauna extinctions.  In fact this paper specifically states the opposite.

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Donald Grayson’s newest book.  His chapter on extinction is marred by gross deception.

Don Grayson, photo by Mary Levin, UW Photography, 2011

Donald Grayson is an archaeology professor at the University of Washington.  

On page 287 of the above book, Grayson wrote “…paleoecologist Jacquelyn Gill and her colleagues took a close look at tiny bits of Ice Age history extracted from 3 lakes and marshes in New York and Indiana.”    Grayson fails to mention the data from the lakes in New York was gathered in a study led by Guy Robinson (1).  (I will number the studies mentioned in this blog post and list them below.)  Guy Robinson’s team took samples of sediment from some New York lakes and marshes, radiocarbon dated different chronological layers of it, and measured and analyzed the volume of pollen, charcoal, and dung fungus spores in each layer.  The volume of dung fungus spores is used as a proxy to estimate populations of megafauna.  They determined local extinctions of megafauna were staggered throughout 2 thousand years, and they concluded this ruled out climate change as a cause of the megafauna extinctions.  If climate change caused the extinctions, they believed the extinctions at these different sites would be simultaneous.  Instead the local extinctions occurred at different times at different sites, and it appears as if nomadic humans were overhunting megafauna at 1 site, then moving on to another, though these local extinctions occurred shortly before the Clovis cultural era.  Increases in charcoal while megafauna populations were declining is additional evidence of probable human impact.  Jacquelyn Gill, the lead author of the paper (2) Grayson referred to in his book,  details a similar study of an Indiana lake.  The authors of this study also found that megafauna populations declined before the Clovis cultural era but also before climate caused changes in the local plant composition.  They believe human impacts are still a “plausible” cause of megafauna extinction, and they wrote “our data thus rule out the hypothesis that (i) climate-forced changes in vegetation drove the megafaunal decline, and (ii) no-analogue plant communities were created by megaherbivory.”  Megafauna became locally extinct here before the pollen evidence suggests changes in the plant community occurred.  They believe humans can still be implicated in megafauna extinctions at this site because increases in charcoal indicated humans were setting fire to the landscape during the period of megafauna decline, and there is evidence of human butchery of mammoths in southeastern Wisconsin during this same time period, suggesting that humans were likely hunting them at this location as well.

It is very dishonest of Grayson to imply these studies support climate-change models of extinction when the authors of these studies specifically state the opposite.  He should have at least informed his readers of their conclusions and explain why he has a different interpretation of the data.  The authors of these studies do note that megafauna decline occurred during a warm phase of climate, but they believe, if climate played a role, it had to be some other mechanism besides climate-driven changes in the environment.  The accepted logic behind climate change models of extinction is that changes in climate decreased the plant foods necessary to maintain viable populations of megaherbivores.  These studies show this is not the case.  Moreover, fossil coprolites show the plants Ice Age megafauna ate are still common on the landscape today, and isotopic studies indicate they were not picky feeders, but instead ate a wide variety of foods.  I think the warm climate phase provided a greater variety of edible plant foods for humans, thus increasing human populations which in turn was detrimental to megafauna.

There are many regions in North and South America where the environment did not change substantially during the most recent glacial-interglacial transition including the pampas of Argentina, southern California, and southeastern North America, especially Florida and the coastal plain.  Climate change models of extinction just don’t make sense in these regions.  Most species of megafauna enjoyed continent wide distributions, and they endured 30 glacial-interglacial transitions over the past 2 million years without suffering extinctions, yet they did become extinct about the same time man appears in the archaeological record.  This can’t be coincidence.

Grayson focuses his arguments against overkill on the Clovis blitzkrieg model of extinction.  This model proposes humans rapidly overhunted megafauna to extinction within the 500 year period of the Clovis cultural era.  There is another model of overkill: humans were responsible for overhunting megafauna, but it took place over several thousand years and also involved a change in fire regime and other human impacts.  This is known as the protracted overkill model and it is the one I favor.  Grayson ignores this model.  He doesn’t acknowledge the likelihood that pre-Clovis humans impacted megafauna populations.  I’m sure he would point out the lack of archaeological evidence for this.  His main objection to the blitzkrieg model is also a lack of archaeological evidence…he believes there are not enough kill sites (direct evidence that humans killed a beast) to justify the overkill hypothesis.  This objection is unreasonable.  99.999…etc% of the individuals of a species that ever lived left no fossil evidence at all.  It is ridiculous to expect to find fossil evidence of the last individuals of a species that just happened to be killed by men.  Moreover, Grayson never quantifies how many kill sites archaeologists would need to find before he would be convinced humans were responsible for the demise of the megafauna.  He needs to put an exact number on it or cease his objections.  Despite the odds against it, there are numerous kill sites and evidence of human-butchered megafauna bones.  Grayson dismisses over half of them, sometimes unfairly, though sometimes his skepticism is warranted.

Grayson falsely claims the overkill hypothesis has “little going for it” and he sounds annoyed on pages 279 and 280 of his book when he laments its acceptance in the popular media.  He might be annoyed because in recent years the  overwhelming number of paleoecological and statistical studies suggest man at least played some role in megafauna extinctions.  Grayson glosses over a statistical study led by G.W. Prescott (3) that determined both man and climate played a role in the end Pleistocene extinctions.  But 2 recent studies of worldwide extinction chronology (4) (5) determined extinctions are more closely tied to human expansion than climate change.  In the study led by C. Sandom they note extinctions have been severe in climatically stable regions.  They write: “Human arrival was a necessary factor for extinctions, whereas climate variation was a contributory one, enhancing regionally the effects of anthropogenic impacts on additive rather than synergistic ways.”

References:

(1) Robinson, G.S. ; L.P Burney and D.A. Burney

“Landscape Paleoecology and Megafaunal Extinction in Southeastern New York”

Ecological Monographs 2005

(2) Gill, J.L.; J.W. Williams, S.T. Jackson, K.B. Lininger, and G.S. Robinson

“Pleistocene Megafauna Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America

Science 2009

(3) Prescott, G.W. et. al.

“Quantitative Global Analysis of the Role of Climate and People in Explaining Late Quaternary Extinctions”

PNAS 2012

(4) Aravjo, Bernardo et. al.

“Bigger Kill than Chill: the Uneven Roles of Humans and Climate on Late Quaternary Megafaunal Extinctions”

Quaternary International 2015

(5) Sandom, C. et. al.

“Global Late Quaternary Megafauna Extinctions Linked to Humans, not Climate Change”

Proceedings of the Royal Society 2014

http://rspb.royalsocietypublishing.org/content/281/1787/20133254

 

A Recent Study of Pleistocene Armadillo DNA Yields 2 Surprising Results

January 19, 2017

An extinct species of armadillo ( Dasypus bellus ) ranged throughout southeastern North America during the Pleistocene.  (A much larger species, Holmesima septentrionalis, was restricted to Florida and the lower coastal plain.)  Scientists have described D. bellus , known by the common name of beautiful armadillo, as being remarkably similar to the extant 9-banded armadillo ( D. novemcinctus ).  The most notable difference between the 2 species is size–the beautiful armadillo was twice the size on average as the 9-banded armadillo.  The latter species began to expand its range into southeastern North America from Mexico within the last 150 years, and today is very common and on the increase in the region.  In a previous blog entry I hypothesized the 9-banded armadillo was a dwarf mutation of the beautiful armadillo, and it was currently recolonizing former parts of its range.  (See: https://markgelbart.wordpress.com/2012/08/19/is-the-9-banded-armadillo-dasypus-novemcinctus-a-dwarf-mutation-of-the-pleistocene-species-dasypus-bellus/ ) However, scientists were recently able to extract DNA from 2 Pleistocene-aged armadillo specimens, and they determined the history of the 2 Dasypus species is more complicated and even more interesting than previously thought.

An armadillo I saw at Scull Shoals State Park, Georgia.  2 species of similar armadillos occupied southeastern North America during the Pleistocene including this 1.

Scientists extracted DNA from an armadillo specimen found in Brynjulfson Cave, Missouri and from another specimen excavated from Medford Cave, Florida.  (They tried many other specimens but these were the only 2 that still yielded viable DNA.)  They determined the DNA of the Missouri specimen was distinct enough from modern 9-banded armadillo DNA to be considered a distinct species.  So much to my surprise, the beautiful armadillo is not the same species as the 9-banded armadillo.  But the Florida specimen held an even bigger surprise…it was a 9-banded armadillo and it dated to over 10,000 years ago.  This means both beautiful armadillos and 9-banded armadillos lived in southeastern North America during the Pleistocene.  The former went extinct while the latter was temporarily extirpated from the region but has just recently made a comeback.

The scientist who originally described the specimen from Florida noted its similarity to the 9-banded armadillo but chose to identify it as a beautiful armadillo because that was the species thought to occur there during the Pleistocene.  This individual was as large as a beautiful armadillo, showing that size alone is not enough to diagnose correct species identification.  Unfortunately, most subfossil specimens no longer contain DNA due to permineralization or decay.  All the specimens labeled ” D. bellus ” in the scientific literature should be re-labeled as ” D. species ” until scientists make a more detailed anatomical analysis of the genus, so that these 2 species can be better distinguished.

So why did the 2 species disappear from southeastern North America near the end of the Pleistocene?  Cold arid climate cycles probably caused range reductions and local extinctions, but armadillos likely re-expanded during warmer wetter climate phases.  Today, 9-banded armadillos may use manmade roads to facilitate their range expansion because it’s less strenuous to travel along cleared roadsides (though dangerous because highways are littered with armadillo corpses). During the Pleistocene armadillos probably followed trails trampled clear by herds of megafauna. This facilitated range expansion during favorable climate cycles.  The extinction of the megafauna may have played a role in the demise of armadillos that could no longer expand their range after climate deterioration caused extirpations. This isn’t a completely adequate explanation–Florida never got too cold and dry for armadillos.  The authors of the below referenced study suggest frequent manmade fires may have been detrimental to armadillos.  Native Americans set fire to the woods annually.  Modern day fire suppression may be another reason 9-banded armadillos have been able to recolonize former territory.

Reference:

Shapiro, Beth; Russell Graham, and Brandon Letts

“A Revised Evolutionary History of Armadillos (Dasypus) in North America Based on Ancient Mitochondrial DNA”

Boreas August 2014

 

 

 

 

Pleistocene Mammals of the Levant

January 14, 2017

Long before the stories in the bible supposedly took place, the Levant was a beautiful wilderness sparsely populated by humans.  The Levant is the region encompassing the modern day boundaries of Israel, Lebanon, Syria, Jordan, and Iraq.  For millions of years climatic fluctuations have caused a waxing and waning of 2 different types of environments here–Mediterranean evergreen oak woodlands and Irano-Turanan steppe consisting of deciduous oak trees and grassy understories.  Habitat for both forest species and grassland fauna has been available during every climatic stage.  The region is also a gateway between Eurasia and Africa, so animals from 3 continents converge here, making it rich in diversity.  African species such as elephants, giraffes, rhinos, hippos, gazelles, hartebeest, warthog, macaque, hyena, lion, leopard, cheetah, and Cape Hunting dog formerly lived side by side with Eurasian species including aurochs, bison, horse, ass, camel, deer, wild boar, ibex, wolf, and brown bear.

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Map of the Levant.

The fossil record suggests the fallow deer ( Dama dama ) was the most common large herbivore in the Levant for over 2 million years.  This species prefers fairly dense woodlands, so their abundance in the fossil record surprises me because I always think of this region as arid.  However, during Ice Ages, the climate in the Levant was cooler and rainier than it is today, though drier climate phases did occur cyclically.  The extinct giant deer ( Megaloceros giganteus ) and elk ( Cervus sp. ), known as red deer in Europe, also made the Levant their home.  The wild ibex ( Capra aegargus ), ancestor of the domestic goat ( C. hircus ), was common on rocky hillsides; gazelles, hartebeest, and an extinct species of warthog roamed the grassy plains.

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Fallow deer.

During warmer climate cycles hippos inhabited Lake Kinnaret.  Long chains of lakes often existed along the Jordan River, and during some climatic stages Lake Kinnaret joined the extinct Lake Amora and the Dead Sea to become 1 giant primeval lake known as Lake Lisan.  Oddly enough, geologists believe Lake Lisan was a freshwater lake in the part that covered the current site of Lake Kinnaret, while the rest of the lake was salty.

A primitive genera of elephants known as stegodon became extinct in Africa about 1 million years ago, but they still lived in the Levant for hundreds of thousands of years past their African extinction.  Stegodon survived until the end of the Pleistocene in southeastern Asia.  Two species of elephants roamed the Levant during the Late Pleistocene–the steppe mammoth ( Mammuthus trogontherii ) and the straight-tusked elephant ( Paleoloxodon antiquus ).  The former evolved into the woolly mammoth during a later Ice Age.  Straight-tusked elephants were a temperate species that couldn’t survive the climate deterioration of the last Ice Age in most of Eurasia.  However, the Levant probably provided a refuge for this species then.  I hypothesize humans overhunted straight-tusked elephants to extinction in their final refugia.  And I believe the same fate befell the temperate species of rhino ( Stephanorhinus hemiotoechus ) that occurred throughout Eurasia.  The Levant likely served as a refuge for these 2 species of megafauna during previous glacials, but human populations and/or hunting skills increased enough to permanently eliminate these slow breeding animals sometime within the timespan of the most recent Ice Age.

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Stegodon.

The lion ( Panthera leo ) that lived in the Levant was the same subspecies as the Asiatic lion found today in 1 small area of India–the Gir Forest.  This big cat survived in remote regions of the Levant until the 19th century.  There is still a small population of leopards in the Levant.  Two species of wolves ranged through the Levant–the timber wolf ( Canis lupus ) and the Egyptian wolf ( C. lupaster ).   Though the latter species occasionally interbreeds with golden jackals ( C. aureus ), a genetic study determined they are more closely related to C. lupusA single specimen of Cape Hunting dog ( Lycaon pictus ) was excavated from Hayonim Cave, Israel.  The paper written about this site incorrectly states this as the only fossil material of Cape Hunting dog ever found outside Africa, but fossils of closely related species have been discovered in Alaska and Texas.

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Asiatic lions in Gir Forest–the same subspecies lived in the Levant until the 19th century.

Pleistocene megafauna suffered fewer extinctions in the Levant than in the Americas.  Wildlife there co-occurred for a longer time with low populations of primitive humans and had time to evolve better avoidance strategies.  Moreover, many Levant species that did become extinct in the wild still live on as domesticated descendents.  Nevertheless, most of the megafauna species were extirpated from the Levant by the 20th century.

References:

Marder, Ofer; et. al.

“Mammal Remains of Rantis Cave, Israel and mid to late Pleistocene Paleoenvironment and Subsistence in the Levant”

Journal of Quaternary Science 2011

Stimer, Mary; and Ofer Bar-Yozef

“The Fauna of Hayonim Cave, Israel: A 200,000 Year Record of Paleolithic”

American School of Prehistoric Research 48 2009

The Continent Conquering Human Flea (Pulex irritans)

January 8, 2017

A flea can jump 160 times its own body length–the equivalent of a 6 foot tall human jumping the length of over 3 football fields.  Most of the known 2500 species of fleas are ectoparasites that use this phenomenal jumping ability to leap from the ground to an host or from one host to another.  Scientists believe the human flea was originally a parasite of wild cavies, species of rodents native to South America.  9,000 years ago, South American Indians began domesticating a species of cavy, either Cavia tschudii or C. aperearesulting in the well known household pet, the guinea pig ( C. porcellus ).  The domestication process may have been instigated by the cavies rather than humans.  Cavies likely were attracted to the shelter of human dwellings where they fed on vegetal kitchen scraps.

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The human flea expanded to many times its size. Their toes serve as a lever that helps them jump many times their body length.

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The guinea pig is thought to be the original host of the human flea.  Fur traders spread the flea from South America to North America and across the Bering Strait to Asia.

By 7,000 years ago, guinea pigs were commonly raised in many South American Indian households.  Maintaining a population of 20 individuals yielded about 12 pounds of meat per month, so they served as a valuable source of food, lessening the need to hunt wild animals.  Fleas from guinea pigs made the leap to man and from there they conquered 5 continents.  According to the lead author of the below referenced study, they advanced through a “step by step gift exchange of furs from South to North America and over the Bering Strait.”  Fur traders slept on their skins and left flea larva living in the detritus of flea feces, dried blood, and human skin flakes that accumulated on their unwashed beds.  After mature fleas feed on blood, they lay their eggs in this detritus.  Human fleas were carried along Asian trade routes and they conquered Egypt by 6000 BP.  The Roman armies carried fleas from Egypt to southern Europe, and the Vikings may have carried fleas from North America to northern Europe.

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Roman legions and Vikings carried fleas with them to Europe.  Bubonic plague carried by fleas from rats to humans and back depopulated Europe.  Fleas were responsible for far more deaths than Romans and Vikings.

Human fleas made a colossal impact on human history.  Fleas jumping back and forth between rats and humans spread bubonic plague, a disease that killed an estimated 30%-60% of the European population during the years 1347-1350.  Much of Europe reverted back to wilderness following this depopulation.  The Romans and the Vikings thought they had conquered the world, but they are long gone.  Human fleas are still here and can be found in just about every hotel, even in the finest, most expensive chains.

Reference:

Panagiotakopulo, Eva; and Paul Buckland

“A Thousand Bites–Insect Introductions and Late Holocene Environments”

Quaternary Science Reviews November 2016