Archive for the ‘Pleistocene Mammals’ Category

Pleistocene Pine Voles (Pitymys pinetorum)

October 16, 2018

Evolutionary biologists like to study rodent fossils.  Rodents occur in high population numbers, and their rapid generational turnover means evolutionary change occurs faster than with larger slower breeding animals.  Scientists recently studied pine vole teeth from 2 caves in Kentucky and 1 cave in Georgia that date to the last Ice Age and compared them with modern day pine vole teeth.  Pine vole teeth from Hilltop and Cutoff Caves in Kentucky date to about 30,000 years ago, and the pine vole teeth from Yarbrough Cave in Georgia date to about 23,000 years ago.  Pine voles are still a common species, occurring all across eastern North America.  Despite their name, they prefer living in moist deciduous forests where they tunnel under tree roots and feed on roots, seeds, fruit, fungus, and insects.  Their fossorial existence keeps them safe from owls and hawks, though snakes can enter their burrows.  Pine voles are considered arvicolid rodents because their teeth cusps are in the shape of alternating triangles.  Other common arvicolid rodents include meadow voles, lemmings, muskrats, and cotton rats.

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Pine voles weigh just an ounce.  They mostly live underground but occasionally venture to the surface.

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Pine vole range.  Pine vole is a misnomer.  They prefer moist deciduous woods, not pine forests.  Nobody knows why the common name is pine vole.

The pine vole teeth from the Kentucky Caves show the pine voles living then were the same size as modern day pine voles living in the region.  However, pine voles living in north Georgia during the Ice Age were larger than modern day Georgia pine voles and about the same size as northern pine voles.  Scientists believe this was in response to colder temperatures.  Bergmann’s rule states that animals living in colder climates generally grow to a larger size because they are better able to retain body heat.  The authors of this study can’t determine whether this large size was the result of inbreeding with northern populations of larger pine voles that colonized the region or natural selection of the local population.

Reference:

Martin, Robert; and K. O’Bryan

“Size and Shape Variation in the Late Pleistocene Pine Vole (Mammalia: Arvicolidae: Pitymys Pinetorum) First Lower Molars from 3 Caves in Kentucky and Georgia”

Paludicola September 2014

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A New Study of the Looper Collection

October 9, 2018

Between 1989-1995 Lonnie and Freida Looper hunted for fossils on 19 different gravel bars along the Mississippi River during droughts when the bars became exposed.  These gravel bars are located between Helena, Arkansas and Greenville, Mississippi.  Thousands of years ago, the bones were quickly buried when glacial meltwater pulses flooded the Mississippi River Valley.  The Mississippi River erodes this Pleistocene-aged sediment and deposits the soil and bones on the gravel bars.  For years the Looper family sold replicas of their specimens, but they donated most of the actual specimens to Delta State University.  I don’t think they still sell the replicas, though the Looper’s website remains on the internet.  The Looper family discovered over 550 specimens including 27 species.  A comprehensive study of their collection wasn’t published until 2017.

 

 

 

 

 

 

The Looper family found this Jefferson’s ground sloth claw on a Mississippi River gravel bar exposed during a drought.

During most of the late Pleistocene the Mississippi River entered the Mississippi River Valley through 3 gaps, but all of these flooded following the collapse of the ice dam that unleashed the waters of Lake Agassiz about 12,900 years ago.  Before this the Mississippi River didn’t meander broadly like it does today.  Instead, it was a series of braided channels clogged with sandbars because the water table was much lower then.  Cold glacial meltwater pulses caused cool microclimates within the valley that favored mixed Ice Age woodlands of pine, spruce, ash, aspen, oak, hickory, willow, tamarack, herbs, and grass.  Frequently flooded bottomlands and abandoned dried-out channels hosted alder thickets with beech, walnut, tulip, willow, and grass.  Spruce and jack pine dominated drier upland sites.  These were the types of habitats that supported the animal life represented in the Looper collection.  Some of the species they found were not known to have occurred within the Mississippi River Valley including paleolama, stag-moose, helmeted musk-ox, giant short-faced bear, and manatee.

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Map of the Mississippi River Valley in relation to the ice sheet during the Last Glacial Maximum. This map doesn’t represent the land area that occupied the continental shelf then.

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The Mississippi River resembled this modern day braided river during the Ice Age.

Paleolama mirifica was a species known from the coastal plains of South Carolina and Georgia, and throughout Florida; so the specimen found by the Looper family was a first for the region and evidence for a greater range than was previously known. The manatee was likely an accidental migrant that may have perished because it failed to go south during cool weather.  Manatees can’t survive in water temperatures below 68 degrees F.  The Looper family also collected bones of mammoth, mastodon, bison, white-tailed deer, long-nosed peccary, 2 species of extinct tapir, horse, beaver, giant beaver, Jefferson’s ground sloth, dire wolf, raccoon, black bear, giant tortoise, snapping turtle, soft-shelled turtle, unidentified bird, small-mouth buffalo fish, and flat-headed catfish.  Bones of bison and deer were the most common.

Nina Baghai-Riding, the lead author of this new study, thinks the Mississippi River Valley may have been a migratory corridor for some species.  Cool microclimates along the river may have attracted fauna of northern affinities.  Rivers are also rich in food resources as well because a greater quantity and quality of vegetation can grow in more irrigated environments.  The superior feeding opportunity attracted megafauna as well.

Reference:

Baghai-Riding, Nina; and D. Hunley, C. Beck, and E. Blackwell

“Late Pleistocene Megafauna from Mississippi Alluvium Plain Gravel Bars”

Paludicola December 2017

file:///C:/Users/Owner/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/Baghai-RidingLatePleistocenegravelbarpaper%20(3).pdf

 

How far South did the Extinct Stag-Moose (Cervalces scotti) Range During the Late Pleistocene?

October 2, 2018

A species of extinct deer, slightly larger than a modern day moose (Alces alces), occurred south of the ice sheets during the late Pleistocene.  It is alternatively known as stag-moose or elk-moose, but its scientific name is Cervalces scotti. This giant deer had the long nose of a moose, though its antlers were more like those of an elk.  However, it shared a closer common ancestor with the former.  They inhabited wetlands surrounded by mixed forests dominated by spruce but with significant elements of pine and hardwoods.  Like modern day moose, they fed upon aquatic plants during summer and twigs during winter.  Mastodons occupied a similar habitat and fed on the same foods, so the 2 species often co-occurred together.

Evidence from the fossil record suggests stag-moose were particularly abundant in midwestern bogs left by retreating glaciers.  Stag-moose bones are quite commonly found in Ohio, Indiana, Illinois, and New York.  Surprisingly, they occurred even farther south with isolated fossil remains having been discovered in Virginia, Arkansas, Mississippi, and South Carolina.  The stag-moose remains found in Desha and Philips County, Arkansas and Rosedale, Mississippi are at 34 degrees latitude.  These consist of antler fragments and a jawbone with a tooth.  The stag-moose specimen from Charleston, South Carolina (just a tooth) occurred at 32 degrees latitude.  This is probably close to the southern limits of its former range because stag-moose remains are completely absent from sites in fossil rich Florida.

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Artist’s depiction of the stag-moose.  They were huge. That is a lot of venison.

A stag-moose skeleton found in Chippewa Lake, Medina, Ohio had 1 bone that had attached sediment filled with pollen representing the type of environment it lived in.  The pollen included fir, maple, alder, aspen, birch, hickory, hackberry, hazelnut, ironwood, pine, oak, basswood, elm, spruce, cedar, ragweed, grass, and cattail.  Spruce pollen made up 60% of the total.  It seems likely the type of environment favored by the stag-moose, as far south as Charleston, South Carolina, included various compositional ratios of these species.  I hypothesize stag-moose occurred in the mid-south during cool moist interstadials rather than the coldest driest stages of Ice Ages.  Wetlands would’ve been more common during these climatic phases.  Full blown glacial maximums restricted stag-moose habitat because desert scrub and grassland habitat expanded then.

Although there is no supporting archaeological evidence, I think overhunting by humans caused the extinction of the stag-moose.  Man colonized North America when ice sheets covered most of Canada, thus restricting stag-moose to more temperate regions where humans became common enough to impact their populations.  When the glaciers began to recede, optimal stag-moose habitat increased, but humans had already decimated their populations into extinction.  Modern day moose crossed the Bering land bridge, and ecologically replaced the stag-moose and were able to survive in northern latitudes where human populations remained too scarce to overhunt them.

Reference:

Mcdonald, Greg; R. Glotchober

“Partial Skeleton of an Elk-Moose, Cervalces scotti, from Chippewa Lake, Medina County Ohio”

Research Paper 2017

Were Beringian Wolves Blonde?

September 25, 2018

An extinct ecomorph of the gray wolf (Canis lupus) roamed North America from Beringia to at least as far south as Wyoming during the Late Pleistocene. (See: https://markgelbart.wordpress.com/2016/05/30/beringian-wolves-an-extinct-ecomorph-of-canis-lupus-lived-as-far-south-as-wyoming/ ) Beringia included the unglaciated region of Alaska, the Yukon, and the Bering Strait located north of the Ice Sheet that covered most of Canada then.  The Bering Strait emerged above sea level during Ice Ages.  An ecomorph is the regional variation of a species that differs morphologically from other populations of the same species.  Beringian wolves had bodies closely resembling those of gray wolves, but their teeth and jaws were larger and more robust like those of the extinct dire wolf (C. dirus).  Paleontologists interpret the larger teeth and jaws as an adaptation for preying and scavenging on megafauna.  Isotopic evidence of Beringian wolf bones does suggest they fed upon mammoths, horse, bison, musk-ox, and caribou.  Beringian wolves were not ancestral to modern day Alaskan gray wolves, but they do share a common ancestor.  Genetic evidence suggests Beringian wolves diverged from wolves found in northern China and Mongolia today about 28,000 years ago.  Present day Alaskan wolves descend from a different population of wolves than the Beringian wolves which became extinct about 7500 years ago.

Map showing location of sites where Beringian wolf bones have been discovered and the proposed route from Beringia to Wyoming.  I hypothesize they occurred as far south as the southern Appalachians.

I hypothesize Beringian wolves were an hybrid species originated when gray wolves interbred with dire wolves.  This hypothesis will be possible to test when scientists are able to extract DNA from a dire wolf fossil.  There are thousands of dire wolf specimens from the La Brae Tar Pits, but the tar in the bones prevents DNA extraction.  Many specimens of dire wolf have been found in Florida as well, but humid conditions here cause DNA to deteriorate.  I also hypothesize Beringian wolves were more widespread than the fossil record indicates.  Over much of the continent fossil evidence of canids consists of isolated teeth and bones difficult for scientists to differentiate between gray wolf, Beringian wolf, dire wolf, and even large Pleistocene coyote.  For example 1 wolf tooth found at Ladds Cave in north Georgia was identified as belonging to a gray wolf by 1 paleontologist, but another scientist ruled it fell within the size range of a dire wolf.  Maybe this specimen came from a Beringian wolf.

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80,000 year old mummified wolf pup found in a Yukon gold mine.  Note the coat color.  It’s is a brownish blonde.

During June of 2016 gold miners discovered the mummified remains of a wolf pup.  As the photo shows, it was perfectly preserved.  Carbon dating of the specimen indicated it was older than 50,000 years–the upper limit of carbon dating.  However, the specimen was associated with volcanic ash dated to about 80,000 years BP.  This predates the 28,000 year old divergence between Mongolian wolves and Beringian wolves, so it will be interesting to learn how this specimen relates to later populations of wolves.  Julie Meachen of Des Moines University will lead a study of the pup.

The coat color of this specimen surprises me.  Of all the speculative illustrations of Pleistocene wolves none depict a golden, blonde, or tawny colored coat.  This specimen appears to have a coat color similar to a lion but a little darker.  Perhaps preservation in permafrost for so long changed the original color of the coat but suppose this was the color.  The coat color likely resembled the landscape background of its habitat.  Patches of yellow grass interspersed with bare dirt predominated in Beringia and much of North America during Ice Age stadials when precipitation was scarce and temperatures dropped.  It’s possible packs of yellow dire wolf/gray wolf hybrids lived throughout parts of North America for thousands of years.

Were Southeastern Wolves Feral Indian Dogs?

August 2, 2018

Archaeologists uncovered 10,000 year old dog (Canis familiaris) skeletons at 2 sites in Illinois.  The sites are known as Koster and Stillwell.  This is the earliest known evidence of domesticated dogs in North America, though scientists believe dogs traveled over the Bering Land Bridge with humans as long as 15,000 years ago about the same time they were first tamed.  Late Pleistocene evidence of dogs in America has either faded away or has yet to be found, but they were probably here.  The specimens from Illinois date to the Pleistocene/Holocene boundary.  The Stillwell dog was about the size of an English setter, and these early Indian dogs anatomically resemble coyote/dog hybrids (known as coydogs).  I hypothesize the wolves that lived in southeastern North America until about 1917 may have been Indian dogs that simply reverted to a wild state.

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Audubon’s painting of an Indian dog.  Indian dogs were so wolfish that European colonists often mistook them for wolves.

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Illustration of black wolf pack by Kelly Quinn.

Scientists classified the wolves that lived in southeastern North America until Europeans wiped them out as the red wolf (Canis rufus), but nobody really knows what they were.  A DNA test of a few specimens from Arkansas found they were hybrids of coyote (Canis latrans) x timber wolf (C. lupus), and wolves currently living in eastern Canada also appear to be coyote/timber wolf hybrids.  However, this still doesn’t explain what the now extinct wolves that lived in Georgia, South Carolina, and Florida were.  The so-called red wolf is not well represented in the fossil record, and the few specimens identified as red wolves may actually be coyotes.  They don’t appear in the fossil record until after dire wolves became extinct, and I think dogs brought by humans went wild and occupied the vacant niche created when dire wolves became extinct.  Although southeastern wolves varied in coat color, many were melanistic.  The gene for a black coat color in wolves originated in domesticated dogs and that was passed to the wolf population in the rare instances when wolves mated with dogs.  So I believe the wolves that lived in southeastern North America were feral Indian dogs with perhaps some admixture of timber wolf and/or coyote.  They were a primitive dog that like the dingo and Carolina dog readily reverted to the wild, especially those left behind when Indian tribes moved away from an area or died out.  Audubon almost mistakenly shot some Indian dogs because he reported that they looked just like wolves.  This resemblance may have contributed to their extinction, though diseases brought by the European colonists’ dogs were probably a bigger factor.  Europeans often mistook Indian dogs for wolves and killed them or deliberately exterminated them to prevent them from breeding with their well bred dogs..  A DNA study of the Koster specimen determined modern dogs have none of the earlier Indian dog ancestry, suggesting the ancient Indian dogs are extinct.

The Carolina dog descends from a later lineage of dogs brought by Eskimos about 1000 years ago.  Strange as it may seem, these dogs quickly evolved from long-furred Eskimo dogs well adapted to cold climates to the short-haired “Old Yeller” type dogs at home in the hot humid south.  Like the earlier Indian dogs, Carolina dogs also easily revert to a wild state.

The original Indian dogs may be extinct, but they did leave a modern day legacy. The only genetic imprint they left in modern dogs is a sexually transmitted cancer.  Geneticists found this cancer originated in the ancient Indian dogs and was passed on to modern dog breeds.

Reference:

https://www.sciencenews.org/article/dogs-lived-and-died-humans-10000-years-ago-americas

The Adaptability of Pleistocene Peccaries

June 30, 2018

Two lineages of peccaries lived all across North America for over 5 million years but both became extinct about the time man appears in the archaeological record.  The long-nosed peccaries in the Mylohyus genus were forest edge species, and the flat-headed peccaries in the Protherohyus-Platygonnus genuses inhabited scrubby thickets.  A new study looked at dental microwear and bone chemistry in these lineages and compared them with the teeth and bone chemistry of the extant white-lipped peccary to determine the dietary similarities and differences of the extinct and extant species of peccary.  Peccaries in the Mylohyus genus co-existed with Protherohyus peccaries during the Miocene over 5 million years ago.  The former ate more woody browse and forest vegetation, while the latter mostly ate grass.  During the Pliocene between 5 million years BP-2million years BP both Mylohyus and Platygonnus ate mostly woody browse in Florida.  Their diets shifted during the early-mid Pleistocene with an increased consumption of grass.  During the late Pleistocene Mylohyus ate more forest vegetation such as twigs, acorns, and nuts, while Platygonnus ate more tough leaves and grass.  This study shows how adaptable these lineages were to environmental change–their diets shifted with changes in climate.  It seems obvious to me that overhunting and/or disruption of the overall ecosystem by humans, not whole scale environmental change, caused the extinctions of both Mylohyus and Platygonnus.  Surviving extant species of peccaries live in deserts and remote jungles where human populations remain sparse.

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Illustration of Platygonnus peccary.

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White-lipped peccaries eat forest vegetation.  They can be dangerous.

The proliferation of feral pigs (Sus scrofa) in North America today demonstrates how favorable the environment still would be for Pleistocene peccaries, if they still existed.  Pigs co-evolved with humans in Eurasia to produce large litters, making them capable of surviving human hunting pressure.  Pigs produce litters of 8-12, but peccaries only birth 2-4 young.

Some archaeologists reject the likelihood that humans hunted peccaries to extinction because there are no known kill sites, other than a peccary shoulder blade with a spear hole in it next to a spear.  See: https://markgelbart.wordpress.com/2014/03/10/the-sheridan-cave-pit-fossil-site-in-wyandot-county-ohio/

This is a ridiculous assumption. There are also no known white-tailed deer kill sites in the archaeological record, but we know Indians hunted deer.  Evidence humans killed Pleistocene peccaries simply faded away over time.

Reference:

Bradham, J. et. al.

“Dietary Variability of Extinct Tayassuids and Modern White-Lipped Peccaries (Tayassu pecari) as Informed from Dental Microwear and Stable Isotope Analysis”

Palaeogeography, Palaeoclimatology, Palaeoecology April 2018

 

An Anatomical Comparison Between the Extinct North American Cheetahs (Miracynonyx sp.) and the Late Pleistocene/Holocene Cougar (Puma concolor)

May 28, 2018

One of my readers recently asked whether the cougar (Puma concolor) might be the same species as the extinct North American cheetahs (Miracynonyx inexpectatus and M. trumani).  This is not as ridiculous a question as a layman might think because paleontologists often mistakenly identify multiple species from fossil remains that after re-evaluation are eventually determined to be from 1 species.  I love reading articles about vertebrate paleontology, but I usually skip over anatomical descriptions because they are pretty dry.  But to answer his question, I used google to search for a paper comparing the anatomical differences between Puma and Miracynonyx.  I did not find a journal article with a comprehensive anatomical comparison between the 2, but I did recall a paper I’d already read that discussed some of the differences.  I’ve linked the paper below in  my references.

Cougars and North American cheetahs had different-sized teeth.  Cougars have larger canines and lower molars than North American cheetahs, but they have smaller lower premolars (p4) and smaller upper pre-molars (P3).  They also have a “less reduced protocone on upper premolar P4.”  North American cheetahs had longer limbs than cougars as the below photos from the linked paper show.  So the answer is no.  Cougars were definitely not the same species as the North American cheetahs.

Fossil history of the panther (Puma concolor) and the cheetah-like cat (Miracinonyx inexpectatus) in Florida - Page 208

Comparison of limb bones between cougar and North American cheetah shows the latter had longer hind foot bones and were better runners.

Fossil history of the panther (Puma concolor) and the cheetah-like cat (Miracinonyx inexpectatus) in Florida - Page 210

North American cheetahs had longer front foot bones as well.

Cougars and North Americans cheetahs are closely related, however.  Genetic evidence suggests their shared lineage originated 6-8 million years ago, and a puma-like cat, probably Puma pardoides, crossed the Bering Land Bridge from Asia shortly after this.  In North America the puma-like ancestor diverged into 3 lines: cougars, North American cheetahs, and jaguarundis. The Puma genus diverged from Miracynonyx about 3.2 million years ago.

The fossil evidence shows M. inexpectatus  lived all across North America from the late Pliocene to the middle Pleistocene (~3 million years BP-~300,000 years BP).  In the Florida Museum of Natural History there are 47 records in state of M. inexpectatus at sites thought to date from the Pliocene to the mid-Pleistocene, but they are known from just 1 late Pleistocene site in Florida.  This site is named Lecanto 2A. The only other Late Pleistocene site with a possible M. inexpecatus  fossil (1 leg bone) is in Cavetown, Maryland.  These specimens can’t be radio-carbon dated.  The reason the specimen from Lecanto 2A is considered Late Pleistocene is its association with specimens of other species known from this age including dire wolf, Florida spectacled bear, rice rat, and cotton rat.  It’s possible there were relic populations of M. inexpectatus  still living during the Late Pleistocene, but it seems more likely it’s a case of older fossils getting mixed with younger fossils.

M. inexpectatus  expanded its range at a time coinciding with the expansion of grassland habitat.  Its long legs helped it run down prey.  M. trumani was even more adapted for living in open habitat.  This species appeared during the Late Pleistocene and was restricted to western North America as far as we know from the fossil record.  M. trumani is probably a descendent of M. inexpecatus which had intermediate characteristics between cougars and M. trumani. 

The paleobiology database indicates cougar fossils dating to the Early and Mid Pleistocene in California, Idaho, Washington, and Mexico have been reported.  Nevertheless, cougar fossils predating the Late Pleistocene are rare.  In the Florida Museum of Natural History there are 44 records of cougar from the Late Pleistocene but just 2 from the Mid Pleistocene and 2 from the Early Pleistocene.  The early Pleistocene specimens are referred to as Puma lacrustis, but I searched for this scientific name on google and found nothing, so I’m not sure what these specimens actually were.  Genetic evidence suggests cougars were well established in South America between 300,000 years BP-200,000 years BP, and this corresponds with the widespread fossil evidence of this species throughout North America during this time period.  I hypothesize cougars began to expand their range widely during an early Rancholabrean interglacial from a regional ancestral population undetected in the fossil record.  This time period would correspond to when forested conditions expanded.  Cougars are ambush predators that prefer forests and woodlands.

North American cheetahs are not as closely related to Old World cheetahs as previously thought.  Physical similarities between the 2 are just another example of convergent evolution.

References:

Barnett, Ross; et. al.

“Evolution of the Extinct Sabretooth and the American Cheetah-like Cat”

Current Biology 15 (5) August 2005

Culver, M.; W. Johnson, J. Pecon-Slattery, and S. O’Brien

“Genomic Ancestry of the American Puma (Puma concolor)

Journal of Heredity 91 (3) 2009

Morgan, Gary and Kevin Seymour

“Fossil History of the Panther (Puma concolor)  and the Cheetah-like Cat (Miracynonxy inexpectatus) in Florida”

Bulletin of the Florida Museum of Natural History 1997

http://ufdc.ufl.edu/UF00095787/00001/1j

 

 

Recent Items about the Late Pleistocene in the News

May 10, 2018

3 stories relating to the late Pleistocene recently made the mainstream news.  The first story is about the upcoming resurrection of the woolly mammoth (Mammuthus primigenius).  George Church of Harvard University is using CRISPR technology to genetically engineer a woolly mammoth by editing Asian elephant (Elephas maximus) DNA.  (I explained CRISPR technology in a previous blog entry.  See: https://markgelbart.wordpress.com/2016/07/22/possible-resurrection-of-the-mammoth-as-early-as-2018/  ) Scientists at Church’s lab are going to edit in the phenotypical characteristics that make the woolly mammoth able to survive in cold wet climates with extremely short and long days.  These characteristics include a layer of fat, long oily hair, small ears, the ability to withstand cold temperatures, and adjustments to the circadian rhythms animals that live in the Arctic require.  They think they can produce a genetically engineered woolly mammoth by 2019.  Scientists hope to eventually engineer herds of woolly mammoths that can live in Siberia where their activities will convert the tundra landscape into a grassy steppe.  Ecologists believe a grassy steppe environment will better prevent permafrost from melting, thus mitigating anthropogenic global warming.  I’m all in favor of resurrecting herds of woolly mammoths, but I believe their goal of mitigating global warming is a pipe dream, and I doubt woolly mammoths could survive in the present day tundra.  I suspect woolly mammoths were confined to relic steppe habitat during interglacials.  Climate is a much greater influence on sub-Arctic habitat than the activities of megafauna.  Woolly mammoths could probably survive today on the grassy Tibetan steppes but not in the Siberian tundra.  The mammoth steppe of the late Pleistocene was more like the modern Tibetan highlands than the Siberian tundra.

The 2nd story reported the results of a statistical study that determined the average size of mammal species has declined over the past 130,000 years, and the authors of this study squarely blame man.  Humans have been overhunting large mammals that reproduce slowly to extinction, leaving smaller species that can better replenish their populations with faster breeding.  Rabbits breed faster than mammoths and elephants.  The average size of a North American mammal species during the late Pleistocene was 216 pounds compared with the average North American mammal species of today which weighs 16 pounds. This decline in body size is unprecedented over the past 65 million years and hasn’t occurred since the extinction of the dinosaurs.  The fossil record is pronounced…this statistical study just confirms the obvious.

Evidence humans may or may not have tracked a ground sloth in New Mexico is perhaps the most interesting story.  There are thousands of late Pleistocene-aged animal tracks in the White Sands National Monument.  During the Ice Age weather patterns were different due to altered climate cycles, and southwestern North America was much wetter than it is today.  The site of these tracks, presently a desert, was a lake shore then.  The animals walked on the edge of the lake in the mud and the tracks have been preserved for thousands of years.  Scientists found human tracks adjacent and actually within ground sloth tracks.  Ground sloths usually walked in a straight line, but these tracks appear to show the ground sloth zig-zag, as if it was avoiding a predator.  There are 2 sets of human tracks.  One human was directly following the ground sloth–his steps are inside the ground sloth steps; the other human was walking very gently beside the other person, as if on tiptoe.  The ground sloth circled around and appeared to rise up on its legs and bare its claws.  There are claw marks in the ground too.  Scientists suggest 1 human was distracting the ground sloth, while the other was sneaking up on it to deliver a fatal spear thrust or blow to the head with a club.  The end result is not recorded in the tracks.  Other scientists are skeptical of this interpretation.  Some think it unlikely humans would hunt the sloth in such an open landscape.  However, this site was not as open then as it is today, and humans could easily outpace a ground sloth.

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Human footprint inside sloth print.  The sloth print is 22 inches long.  The human footprint is 5 inches.  The sloth had a wider stride, so the human must have been hopping to get his foot inside the sloth’s print.

I wish there were more mainstream news stories about the late Pleistocene.  It’s much more interesting than waiting for Donald Trump to get impeached.

References:

Daley, J.

“Fossil Tracks May Record Ancient Human Hunting Sloth”

Smithsonian April 20, 2018

Smith, F.; et. al.

“Body Size Downgrading of Mammals over the Late Quaternary”

Science  April 2018

Speculative Distributions of Megafauna in Georgia 36,000 years BP

April 15, 2018

A recent statistical study estimated the abundance and natural ranges of megafauna species (mammals over 40 pounds), if man didn’t exist today.  They analyzed 5,742 megafauna species that have existed over the past 130,000 years, a time span including a full glacial/interglacial cycle.  Not surprisingly, they concluded the natural ranges and abundance of megafauna would be much greater today, if not for man.

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Maps showing natural ranges and abundance of megafauna.  The top shows today’s abundance.  The bottom shows abundance today, if man didn’t exist.  Map is from the below reference.

This study inspired me to draw speculative range maps for selected megafauna species that lived in Georgia 36,000 years ago–long before people ruined the wilderness.  I chose this time period because it was an interstadial, a warmer wetter climate phase within the last Ice Age, and I think wildlife populations were higher then than during the Full Glacial Maximum when at least some of Georgia consisted of desert-like habitat.  My maps are educated guesses because the Pleistocene fossil record of Georgia is extremely incomplete.  Megafauna populations were not evenly distributed throughout the state.  I assumed the northern part of the state held more forest and woodland, while the southern half hosted more grassland.  But both environments existed in most of the state, often side-by-side.  Therefore, forest and forest edge species such as tapirs and long-nosed peccaries were more abundant in the northern part of the state.  Bison and horse were more numerous on the coastal plain.  Some animals migrated in and out of the state.  Isotopic evidence suggest mastodons moved back and forth between Florida and Georgia.  Like leaders of today’s elephant herds, experienced matriarchs knew where rich sources of food and mineral licks were located.  Some herds of mammoths probably moved great distances as well.  Flat-headed peccaries likely favored the sand hill scrub habitat along the fall line.

Evidence of caribou in north Georgia dates to the Last Glacial Maximum, but I believe they were so abundant even during interstadials that some herds wandered as far south as Georgia.  There is no fossil evidence of helmeted musk-ox, stag-moose, giant lion, or saber-tooth in Georgia.  I’m certain giant lion and saber-tooth did range into Georgia, and it seems probable helmeted musk-ox and stag-moose did as well.  Fossil evidence of giant lions has been found in Florida and Mississippi.  Saber-tooth bones have been recovered from all the states surrounding Georgia.  Fossil remains of stag-moose and helmeted musk-ox have been excavated from sites on the same latitude as Georgia.

The dots on my maps don’t represent any specific numerical value, but the bigger ones indicate larger populations. The maps include the 10,000 square miles of continental shelf that was above sea level between ~83,000 years BP-~7800 years BP.

Range maps of selected megafauna species in Georgia 36,000 years ago.  Click to enlarge.  I know the labels on the maps are hard to see so from left to right on the top row they are mastodon, mammoth, Jefferson’s ground sloth, stag-moose, stout-legged llama, large-headed llama.  Middle row from left to right: long-horned bison, horse, long-nosed peccary, helmeted musk-ox, giant beaver, saber-tooth.  Bottom row from left to right: tapir, caribou, flat-headed peccary, giant lion, jaguar, dire wolf.

Reference:

Faurby, S; and J.C. Svenning

“Historic and Pre-Historic Human-Driven Extinctions have Reshaped Global Mammal Diversity Patterns”

Diversity and Distribution 21 (10) Augusts 2015

The Late Pleistocene Extinction of Leopards (Panthera pardus) from Sumatra

March 8, 2018

During temperate climate cycles of the Pleistocene leopards enjoyed an even wider geographic range than they do today, living in Europe as well as Africa and Asia.  Leopards colonized the island of Sumatra during the middle Pleistocene but became extinct there at the end of the Pleistocene, despite continuing to thrive elsewhere in Asia.  Scientists used a statistical model to determine why leopards disappeared from Sumatra.  They considered all potential competing carnivores and total prey biomass in their calculations.   Leopards shared Sumatra with orangutans, monkeys, humans, elephants, deer, tapir, pigs, sun bears, tigers, clouded leopard, Asian golden cats, and dholes.  Tigers are known to depress leopard populations in regions where the 2 species overlap; and dholes, a pack-hunting dog, compete for the same large prey species.  Scientists expected the model to show competition with tigers and dholes caused the extinction of leopards on Sumatra.  However, when they removed the influence of these 2 species from their model, leopards still became extinct.  Leopards also became extinct when humans were removed from the simulation.  Surprisingly, the statistical simulation suggests competition with clouded leopards (Neofelis diardi) and Asian golden cats (Pardofelis temminckii) caused the extinction of leopards on Sumatra.

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Location of Sumatra.

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Asian golden cats.  This species along with clouded leopards outcompeted leopards on Sumatra following the end of the Pleistocene.

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Clouded leopard.

The authors of this study propose ecological changes following the end of the Pleistocene greatly favored smaller forest cats over leopards.  During Ice Ages Sumatra was a mix of savannah, woodland, and forest; but wetter climate fostered the spread of thick forest.  Larger prey species became less common, so leopards were forced to compete with the smaller cats for smaller prey items.  Both of the smaller species of cats reproduce faster than leopards and produce larger litter sizes.  The extremely adaptable leopard was actually squeezed out of its ecological niche on Sumatra by 2 smaller felines.

Adult leopards weight between 80-200 pounds compared to a maximum of 57 pounds for clouded leopards and 35 pounds for Asian golden cats.  The latter 2 species are efficient predators of small animals and need less food than leopards, giving them an advantage when available protein biomass declines.

Clouded leopards are 1 of the most primitive species of living cats and may be related to the evolutionary link between big and small cats.  The Sunda clouded leopard is the species that lives on Sumatra.  It diverged from the other species of clouded leopard ((Neofelis nebulosa) about 70,000 years ago.  Clouded leopards from Borneo crossed a now submerged land bridge and colonized Sumatra following the Tuba volcanic eruption that wiped out much of Sumatra’s wildlife ~70,000 years BP. The Sunda clouded leopard was not recognized as a separate species until 2006.

Reference:

Volmer, R.; et. al.

“Did Panthera pardus (Linneaus 1758) become Extinct in Sumatra because of Competition for Prey?  Modeling Interspecific Competition within the Late Pleistocene Carnivore Guild of the Paday Highlands, Sumatra”

Paleogeography, Paleoclimatology, and Paleoecology 2018