Cave ACb-3 in Colbert County, Alabama

Rain water began eroding a limestone outcrop located in what today is northwestern Alabama over 228,000 years ago.  The slightly acidic rain dissolved the rock in all directions creating what is known as a phreatic cave system.  Crevices provided shelter for small animals including wood rats, squirrels, rabbits, shrews, spotted skunks, bats, lizards, and snakes.  Scientists have yet to describe the remains of these smaller creatures in the scientific literature, demonstrating that the amount of fossil material available for study exceeds the time qualified scientists have to study it.  About 172,000 years ago rain water began channeling through 1 stream in the cave, creating a rectangular trench.  This is known as a vadose cave because it has a dome shaped ceiling with a rectangular floor.  A cave entrance enlarged allowing big mammals such as  Jefferson’s ground sloth, beautiful armadillo, white tail deer, long-nosed peccary, tapir, giant beaver, bobcat, wolf, and sabertooth inside.  This composition of species suggests a wooded environment prevailed locally.

The abundant speloethems (cave formation mineral deposits) and their positions gave scientists the opportunity to date the fossil remains, or rather to bracket the age range within which these vertebrates lived.  The bone-bearing sediments were found underneath and between calcium carbonate flowstone that could be dated using uranium-thorium dating.  (Coral can also be dated using this method.) Uranium 234 decays to thorium 230 at a known rate and by measuring the amount of each and by plugging the values into a mathematical formula, scientists can determine the age.  Uranium-thorium dating can date objects up to 500,000 years old, far exceeding the 50,000 year limit of radio-carbon dating.  Uranium-lead dating can be used to estimate the age of an object that is billions of years old.  Cave ACb-3 accumulated vertebrate remains between ~228,000 BP-~121,000 BP, roughly coinciding with the Illinois Ice Age and the Sangamonian Interglacial.  After this, the cave entrance became sealed until recently.

Calcium carbonate flowstone in a cave. 

Types of cave formations.  They can be dated using Uranium-Thorium series dating.

A few years ago, Sharon Holte studied the 7 skeletons of Jefferson’s ground sloth that were found in this cave, and she wrote about her findings in her Masters Thesis.  She found injuries on the shoulder blades and arm bones that suggested intraspecific fighting.  The males likely sparred over mating rights.  Ground sloths had powerful arms and huge claws and could have easily killed an unarmed man with raking paw blows.  However, ground sloths had thick fur and armor, enabling them to endure intraspecific battles most of the time.  Sharon Holte also speculates body change occurred over time within the population of Jefferson’s ground sloths.  They evolved from stout and robust during cooler climate phases to longer and thinner during warmer climate phases.  I think the sample size from this cave is too small to come to any conclusion about evolving body shape.

Ground sloth shoulder blade from specimen found in Iowa.  Shoulder blade and arm bones of Jefferson’s ground sloths found in Cave ACb-3 show evidence of intraspecific fighting.

References:

Holte, Sharon

“Description of Jefferson’s Ground Sloth (Megalonyx jeffersonii) from ACb-3 Cave, Colbert County, Alabama, with comments about Ontogeny, Taphonomy, Pathology, and Paleoecology”

Masters Thesis East Tennessee State University 2012

Lively, R.S.; G. L. Bell, and J.P. Lamb

“Uranium-Series Dates from Travertines Associated with a Late Pleistocene Megafauna in ACb-3, Alabama”

Southeastern Geology 1992

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Evidence Humans Butchered a Jefferson’s Ground Sloth in Ohio 13,700 years ago

Some time prior to World War I, R.C. Niver found the bones of a Jefferson’s ground sloth (Megalonyx jeffersonii) and a bison on his family’s farm located near Norwich Township, Ohio.  The bones were unearthed fom 4 feet below the surface of a bog.  It’s unknown whether he was attempting to drain the swamp by digging a ditch, ploughing, or deliberately looking for fossils.   The bones were examined by the late Oliver Hay, one of the leading paleontologists of the day.  Eventually, the ground sloth bones were placed in a box mislabled as mastodon and put in the attic of the obscure Firelands Historical Society Museum where they rested for over 80 years.  One day, Matthew Burr was cleaning the attic, and he rediscovered the ground sloth bones.  Furthermore, he noticed cut marks on the bone.  Although many paleoecologists believe humans overhunted ground sloths into extinction, before Mr. Burr’s astonishing observation, no direct evidence of human exploitation had ever been reported from the archaeological record.

Photo of the bog where researchers think the ground sloth bones were originally discovered.

The ground sloth bones rested in a box labeled as mastodon in the attic of the Firelands Historical Society Museum for many decades.

Brian Redmond, a curator of the Cleveland Museum, examined the bones.  He counted 5 chop marks and 41 slice marks on an upper leg bone. (Claws, ribs, an ankle, a knee cap, and the lower leg were the other bones found along with the femur.)  Of course, the material was studied thoroughly to discount fraud and other types of morphology such as trampling or river scouring that can produce scratches that resemble anthropogenic marks.  They looked at the marks with a scanning electron microscope and confirmed they were made while the bone was fresh, and they learned they were made with 2 different stone tools.  The placement of the marks also made sense from a butcher’s point of view.  The Indian butcher cut the muscles from the most efficient angles.

There are visible cut marks on this ground sloth femur.  It’s a one of a kind specimen.  The cracks are the result of drying after the specimen was retrieved from the wet bog.

Though the Ohio ground sloth is the best direct evidence that humans exploited ground sloths, 2 other sites yielded assumed evidence.  Scientists found dermal ossicles of a Harlan’s ground sloth at the Kimmswick site in Missouri.  Kimmswick is a confirmed mastodon kill site.  Dermal ossicles make up the armor that used to help protect ground sloths from predators.  Like their cousins, armadilloes and glyptodonts, ground sloth skin was covered in armor, but theirs was covered with thick fur.  The scientists who studied the Kimmswick site believe the dermal ossicles came from a sloth hide carried by paleo-Indians to the mastodon kill site.  The hide later rotted away but the ossicles endured.  The other site is in South America where sloth bones were found associated with human artifacts.

Artist’s rendition of a Jefferson’s ground sloth.  They weighed over a ton.  The Ohio specimen discussed here was one of the largest individuals ever discovered.

Only 3 Jefferson’s ground sloth bones have ever been found in Ohio.  It’s an amazing coincidence that 1 of them showed evidence it was probably killed by humans.  The Indians may have been scavenging it, but I doubt it.  I’m sure they directly killed it.

13,700 years ago, the Laurentide Glacier had retreated northward from Ohio and Lake Erie was young, and recently filled with glacial meltwater.  The climate was rapidly warming but still quite cold during winter.  But as I wrote  in a previous blog entry, these  beasts with neotropical origins could survive cooler climate because they dug deep underground burrows. https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/

It’s sad that these amazing beasts no longer walk the earth.  When the paleo-Indians hunted them, they probably never imagined they were in the process of completely wiping them out.  They likely had no concept of extinction because they lived in a world of bounty.  To them, a ground sloth was an easy feast in a world before grocery stores existed.  (Incidentally, in his book How to Get out of the Rat Race and Live on $10 a Month George Leonard Herter claims that tree sloth tastes like pork.)  Ground sloths were well adapted to defend themselves against big cats and wolves, but they were helpless against projectile weapons.

Reference:

Lepper, Bradley

“Pre-Clovis Butchered Ground Sloth in Ohio”

The Mammoth Trumpet 28 (1)  Jan 2013

Top Ten Pleistocene Animals I would bring back to the Present, if I could

(Warning: I’m jumping on my soapbox for this blog entry.)

Merry Christmas?  I say bah humbug!  Christmas is an ancient pagan holiday celebrating the winter solstice–the shortest day of the year–with a festival of artificial lights.  The Romans knew how to party, and they turned this festival into a drunken orgy known as Saturnalia.  They gave toys to their kids to distract them, so the children wouldn’t be aware that their parents were engaged in a little joyful wife and servant swapping.  The Catholic Church gained political power in the 4th century, but the hierarchy was unable to stop the alcoholic sex-crazed fun.  Instead, they incorporated the holiday and falsely claimed it to be the birthday of Jesus, the invisible Jewish rabbi who the psychotic founders of Christianity believed was the son of God, after God supposedly deposited his sperm into Mary’s vagina without breaking her hymen.

Pious Christians tried to break the real spirit of what the winter solstice should be about, but they haven’t ruined it nearly as much as the oppressive rulers of today’s American society have.  Big corporations and monstrous merchants have transmogrified this glorified sex orgy into a psychological compulsion for working class people to waste money on a bunch of junk they don’t need, so that wealth is transferred from the poor to greedy merchants.  Clueless economists make the ridiculous claim that this is good for the economy.  In reality it’s only beneficial for credit card-owning banks who for the rest of the year use this expensive spending orgy to drain working class people’s money, like vampires sucking the blood of sheep.

I’m not interested in material objects, but I do have a Christmas wish that a magic Santa could transport live specimens of extinct Pleistocene animals to the present so scientists could study the beasts, and zoos could display them.  Here’s my top ten wish list:

Photo of a replica skeleton of Ermeotherium that I took at the Skidaway Island museum.

1. Eremotherium laurillardi–a giant ground sloth.  There’s nothing like this beast living today.  Diminutive South American tree sloths are the closest living relative, but c’mon, there’s just no comparison.  This massive beast lived on Georgia’s coastal plain until about 30,000 years ago which is the time the last glacial maximum began.  The climate became too cold for them in North America, but they persisted in South America until about 11,000 years ago.

2. Smilodon fatalis–the saber-toothed cat.  There’s nothing like this alive today either.  Maybe we could lead a horse or cow into its cage and solve the mystery, once and for all, how it killed its prey.

3. Glyptotherium floridanum–Glyptodont.  A mammal built like a turtle and the size and shape of a Volkswagon.  Who wouldn’t want to see this in person?

4. Mammut americanum–Mastodon.  I’d pick mastodon over mammoth.  Mammoths are closely related to extant living Asiatic elephants, but mastodons were much more primitive and were related to an ancient order close to the evolutionary foundation of elephant-like animals.

5. Megalonyx jeffersonii–Jefferson’s ground sloth  This was a smaller ground sloth about the size of an ox.  For ecological reasons I believe this was the most common kind of ground sloth found in Georgia during most of the Pleistocene.  It preferred forested environments and was better adapted to colder temperatures, living as far north as Canada.

6.  Glossotherium harlani–Harlan’s ground sloth. Co-existed with Jefferson’s ground sloth, but apparently preferred open meadows as opposed to the forested conditions frequented by the other.

7. Mammuthus colombi–Columbian mammoth.  An elephant adapted for living in a temperate region.  Definitely unique enough to make my Christmas wish list.

8. Dinobastis serum–Scimitar-toothed cat.  Not as famous as Smilodon but equally as fascinating.  Got to give it the edge over other mammals left off the top ten list such as the Pleistocene vampire bats, extinct javelinas, and extinct llamas.  Though interesting, those other species do have similar living relatives, but there are no species of fanged cats left on the planet.

9. Terratornis sp.–The terratorn.  It’s a condor with a 14 foot wingspan.

10. Hesperotestudo crassicutata–This giant tortoise lived on Georgia’s coastal plain during warm interglacials and interstadials.  It grew as big as modern day Galapagos Island tortoises, but was closely related to extant gopher tortoises.

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The nature lover in me did get a real gift this year in time for Christmas.  The state of Georgia is going to purchase 15 square miles of Oaky Woods in Houston County.  Currently, it’s being managed as a wildlife management area, but real estate developers were threatening to destroy it.  Oaky Woods is a unique wilderness.  It’s the last stand of the black bear in the piedmont region of Georgia, and it’s home to 4 state record trees.  The landscape consists of mature stands of mixed pine and oak as well as rare remnants of blackbelt prairie, a probable relic habitat dating back to the Pleistocene.  Moreover, there is some good fossil-hunting ground there.  Eocene marine fossils are commonly found on this piece of land.

See www.saveoakywoods.com

Augusta radio talk show host, Austin Rhodes, suggested I go live in a tree when I brought this subject up on the Augusta Chronicle message board.  What a jerk!  The site is now protected, however, no thanks to shmucks like him.

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My next entry will be about ice berg keel scours off the coast of South Carolina. 

Cool.