Middle Pleistocene Man (Homo heidelbergensis)

Many late Pleistocene animals evolved from middle Pleistocene ancestors that were different enough to be considered separate species.  Columbian mammoths (Mammuthus colombi) evolved from the southern mammoth (M. meridionalis), a shorter elephant with straighter tusks. Jefferson’s ground sloth (Megalonyx jeffersoni) evolved from Wheatley’s ground sloth (M. wheatleyi), and Smilodon fatalis evolved from the more lightly built S. gracilis, among many other examples.  The same is true for humans.  Both Homo sapiens and H. neanderthalis evolved from H. heidelbergensis, also known as Heidelberg man after discovery of the first specimen in Heidelberg, Germany during 1907.  Genetic evidence suggests modern humans diverged from Neanderthals between 750,000 years BP-550,000 years BP.  The population of Heidelberg man that lived in Europe evolved into H. neanderthalis, while the population of Heidelberg man that lived in Africa evolved into H. sapiens.  (The poorly known Denisovans diverged from Neanderthals.) Fossil evidence of Heidelberg man dates to between 600,000 years BP-300,000 years BP, though undoubtedly it occurred earlier than the fossil evidence indicates.  The oldest evidence of humans in Europe dates to 800,000 years ago and was found in Spain, but these specimens are considered an extinct sister species of Heidelberg man known as H. ancessor.

Artist’s depiction of Homo heidelbergensis.  They were about the same height as modern men and had the same average brain capacity, but their jaws were distinctly different.

The Schoningen spears, 330,000 year old projectile weapons used by Homo heidelbergensis.  They were found in a strip mine in Germany.  Archaeologists found 9 spears, 1 lance, a stick pointed on both ends, and a burned stick along with the remains of butchered horses next to a lakeshore.

Heidelberg man evolved from H. erectus.  Heidelberg man had a more human-like face and a larger brain capacity (averaging 1200 cc compared to 973 cc).  They had the same average brain size as modern day humans, and the main difference between the 2 is the shape of the jaw which was distinct.  Heidelberg man was the first species of human to colonize regions with cold climates.  To survive in harsher climates, they evolved to eat more meat.  In Europe this diet included elephant, rhino, bear, deer, boar, and horse; and in Africa they ate antelope and zebra.  They surely ate many different kinds of plants, but nothing is known of the vegetal part of their diet.  Heidelberg man had control of fire and used tools such as stone hand axes and wooden spears. In 1994 nine spears made of spruce wood were found in a German strip mine, and they dated to 330,000 years BP.  They are known as the Schoningen spears, and they were found associated with butchered horse bones.  Rapid rise of a lake level covered all this evidence in sediment and helped preserve it.

I have no doubt Heidelberg man could speak, though a minority of scientific opinion believes they could not.  The hyoid bone, important for speech, is well developed as are the middle ear bones used for understanding speech.  There is also evidence for right brain/left brain lateralization–one side of the brain is more dominant.  Brain lateralization suggests a brain used to speak and understand speech.  Heidelberg man hunted large mammals, an activity requiring cooperative hunting and therefore speech.

Specimens of Heidelberg man have been found in sites located in Germany, England, France, Greece, India, Zambia, Kenya, Ethiopia, and South Africa.  I tried to find out exactly how many specimens have been discovered worldwide, but as far as I can determine no study has catalogued them all.

Heidelberg man likely occurred in low population numbers, fluctuating with boom and bust climatic conditions, and whole tribes often perished  when important members died.  One site in Germany where Heidelberg remains were found also yielded bones of saber-tooths (Homotherium), lions, leopards, hyenas, bear, elephant, red deer, and horse.  Unlike modern humans, Heidelberg man didn’t always win in competition with the predators they shared the landscape with.

Reference:

Schoch, W.; G. Bigga, W. bohner, P. Richter, and T. Terberger

“New Insights on the Wooden Weapons from the Paleolithic Site of Schoningen”

Journal of Human Evolution 89 December 2015

Did Some Species of Giant Ground Sloths Live in Herds?

At least 22 giant ground sloths (Eremotherium laurillardi) perished in a pond polluted with their own feces over 18,000 years ago.  Scientists excavating this site found 667 vertebrate bones of which 575 were identified as belonging to Eremotherium.  These included the remains of at least 16 adults, 6 subadults, and 1 juvenile.  Fossil feces and gut contents were found alongside the bones.  The site, known as Tanque Loma, is located in Southwestern Ecuador.  Eremotherium was the largest of the extinct ground sloths, roughly the size of an African elephant, and they ranged from South America into southern North America, though they disappeared from the northern part of their range during the Last Glacial Maximum when the climate got too cold for them there.  Eremotherium bones show up in most coastal fossil sites in Georgia.  Fossil sites mostly composed of Eremotherium bones occur in Florida, Ecuador, Brazil, Mexico, and Uruguay; and the circumstances of these mass death sites may be the same.  Large groups of Eremotheriums, attracted to shrinking water holes during droughts, congregated there until they poisoned the water with great quantities of their feces.  The entire group then died within a few days, explaining the mass accumulation of mostly 1 species.  Modern hippos in Africa often suffer the same fate today.

Illustration of Eremotherium along with other Pleistocene animals.  Painting by the late Charles Knight.  Eremotherium may have been less hairy, like humans and elephants.  They were also larger than this illustration indicates.

Mass hippo deaths can occur when they contaminate the water they live in with their own feces.

Some scientists think the occurrence of different age groups at these mass death sites indicates Eremotherium lived in herds.  I doubt this can be determined.  It seems more likely they were simply attracted to the same resource.  Caves accumulate ground sloth remains as well because they were a resource that provided shelter for an animal that had difficulty controlling its body temperature.  Water holes and food items were resources that attracted ground sloths to the same spot, and many of the mothers just happened to be accompanied by young, but they were not necessarily living in organized herds.

Remains of other species found at Tanque Loma include Glossotherium (a smaller probably hairier species of ground sloth), pampathere (a giant armadillo), an extinct species of horse, and a deer related to the modern day whitetail.

Note to paleoecologists:  Nobody has yet studied the plant species composition of the sloth feces and gut contents found here.

Reference:

Lindsey, E.; et. al.

“A Monodominant Late-Pleistocene Megafauna Locality from Santa Elena, Ecuador: Insight on the Biology and Behavior of Giant Ground Sloths”

Paleogeography, Paleoclimatology, and Paleoecology 544 April 15, 2020

https://www.researchgate.net/publication/338565424_A_monodominant_late-Pleistocene_megafauna_locality_from_Santa_Elena_Ecuador_Insight_on_the_biology_and_behavior_of_giant_ground_sloths

A Shocking New Study of Dire Wolf (Canis dirus) DNA

Dire wolves were one of the most common large predators of Late Pleistocene North America, and sub-fossils of this species are common, but scientists have had difficulty finding specimens with enough intact DNA to analyze.  There are thousands of dire wolf fossils excavated from the La Brea Tar Pits in California, but this DNA is contaminated with tar and can’t be used.  There are also many specimens of dire wolf fossils from Florida, but the humidity there causes DNA to deteriorate and become unusable.  However, Angela Perri, a zooarchaeologist from Durham University, made a concerted effort to find dire wolf specimens with enough viable DNA to study, and she found 5 specimens.  Labs from Australia and England analyzed the DNA from these specimens and came to a stunning conclusion–dire wolves were not closely related to gray wolves (Canis lupus) as most paleontologists had assumed, and they were not really even wolves.  Instead, they were the last in a lineage of now extinct ancient canids.

Illustration by Mauricio Anton of dire wolves interacting with timber wolves. Dire wolves were larger and may have had shorter reddish coats.


The genetic study determined the ancestor of dire wolves diverged from the ancestor of gray wolves at least 5.7 million years ago.  The closest living relative of the dire wolf is the African jackal (C. mesomelas), but the ancestor of that species diverged from dire wolf ancestors about 5.1 million years ago.  Interestingly, jackals can interbreed with wolves, but the study of dire wolf DNA found no evidence of interbreeding between gray wolves and dire wolves.  Apparently, the 2 species had been geographically isolated from each other for too long, and when they came into contact did not recognize the other as possible sex partners.  This study casts doubt on my hypothesis that an extinct ecomorph of Beringian gray wolves were a gray wolf/dire wolf hybrid.  (See: https://markgelbart.wordpress.com/2016/05/30/beringian-wolves-an-extinct-ecomorph-of-canis-lupus-lived-as-far-south-as-wyoming/ )
Paleontologists assumed dire wolves were close relatives of gray wolves because their anatomy was so similar.  Dire wolves had broader skulls, bigger teeth, shorter limbs, and were more robust; but otherwise they were much alike.  The similarity can now be attributed to convergent evolution when unrelated species evolve similar traits in response to similar environmental conditions.

Canids originated in North America, but the ancestors of gray wolves, coyotes, and jackals colonized Eurasia and Africa and evolved separately from dire wolves whose ancestors remained in North and South America.  (Dire wolves ranged from Alberta south to Peru and from California east to the Atlantic Coast.)  Dire wolves appear suddenly in the fossil record 200,000 years ago.  Most paleontologists think they evolved from Armbruster’s wolf (C. arbrustrei). No scientist has considered the possibility, but maybe this line evolved from the bone-eating dogs (Borophagus), a group of canids that seemingly disappeared early during the Pleistocene.  Scientists can’t investigate this because no viable DNA from Borophagus dogs remains viable. Dire wolves were adapted to live in climates ranging from temperate to sub-tropical.  Scientists weren’t able to sequence the entire genome of the dire wolf to determine its appearance, but they may have had shorter more reddish coats than gray wolves and probably preferred warmer climates.  The ancestor of gray wolves and coyotes crossed the Bering Land Bridge and colonized North America at least 20,000 years ago and overlapped with dire wolves for about 10,000 years.  Gray wolves co-evolved with humans and learned to fear man.  Dire wolves never learned to fear man, and likely could not compete with humans.  I think this explains their extinction, while wolves and particularly coyotes continue to hang-on.  

The authors of the new study think dire wolves are so different from gray wolves they should be given a separate genus name–Aenocyon.  One of the first paleontologists who looked at dire wolf bones assigned this genus name to dire wolves, but it fell from fashion because of the misconception that dire wolves were close kin to gray wolves.  Turns out he was right; later paleontologists were wrong.

Reference:

Perri, A.; K. Mitchell, L, Frantz; et. al.
“Dire Wolves were the Last of an Ancient New World Canid Lineage”
Nature 2021

Pack-Hunting Cuban Boas (Chilabothrus angulifer)

Cuban boas work together when they hunt Jamaican fruit bats.  They each take a strategic position near cave entrances to increase the chances they will successfully ambush a bat.  Scientists believe the gauntlet they create requires active coordination.  Otherwise, they would all be laying on top of each other in the best strategic location, and bats could just avoid that area.

Cuban boas hunt in packs.  They coordinate their positions near cave entrances and ambush Jamaican fruit bats.  They kill their prey using constriction.

There are 12 species of large boas in the Chilabothrus genus, but each Caribbean Island usually hosts just 1 or at most 2 species.  Each island was colonized by 1 species of boa that drifted there on floating vegetation millions of years ago.  Once that species became established on the island, they precluded other species arriving on floating vegetation from colonizing the island.  Genetic evidence suggests Cuban boas diverged from their closest relative 17-20 million years ago, and since then they have prevented other boa species from establishing a population there.

Cuban boas were part of an unique ecosystem found on Caribbean Islands until it was disrupted by man thousands of years ago.  Cuban boas formerly grew up to 27 feet long, but now individuals larger than 9 feet long are rare.  During the Pleistocene they hunted hutias (large 15 pound rodents), birds, and lizards. They still hunt these species, but larger species of hutias became extinct after man colonized the islands.  Cuban boas may have also hunted the now extinct dwarf ground sloths that roamed the island then.  Cuban boas shared the environment with other predators including Cuban crocodiles, an extinct species of 3 foot tall flightless owl, and large extinct subspecies of barn owls and black hawks.  Since man arrived on Cuba, both boas and crocodiles have evolved to smaller sizes.

The 2 largest predators on Cuba have evolved to a smaller size, since man colonized the island.  Image from the below reference by Rodrigues-Cabrera.

References:

Dinets, Vladimir

“Coordinated Hunting in Cuban Boas”

Animal Behavior and Cognition 4 (1) Feb 2017

Rodrigues-Cabrera, T.; and T. Javier Torres

“An Overview of the Past, Present, and Future of the Cuban Boa, Chilabothrus angulifer, (Squamata: Boidae): A Top Terrestrial Predator on an Oceanic Island”

Reptiles and Amphibians Journal December 2016

A Study of My Seafood Consumption during 2020

90% of the seafood consumed in the U.S. is imported, and most of that is farm-raised.  This is a shocking statistic, considering how abundant fish were in American waters when Europeans first colonized the continent.  I was curious about my own seafood consumption, so I kept a tally of the fish and shellfish I ate in the year 2020.  I tried to avoid the Heisenberg Effect defined as the act of measurement altering the phenomenon under investigation, but I can’t rule out my subconscious influencing the results.  Nevertheless, I usually eat seafood once a week, and I believe this is a fair account of my average year’s seafood consumption.  The following paragraph is the result of my study.

I consumed seafood 76 times during 2020 or about 6.9% of my meals.  The tally is shrimp-13, tilapia-10, salmon-9, catfish-8, tuna-7, crab-4, croaker-3, sardines-3, oysters-3, trout-3, herring-2, crawfish-2, flounder-2, lobster-1, eel-1, Pacific cod-1, and unknown-1.

Pacific white-legged shrimp–small, medium, and large.  I like the largest ones because it takes less work to peel and clean them.  Along with tiger prawn shrimp these are the most common species found in the supermarket.  90% of shrimp consumed in the U.S. come from shrimp raised on farms in the Far East.

Shrimp is the most popular seafood consumed in the U.S. and 90% of it is imported.  It was my single most consumed seafood item as well.  Most of the shrimp consumed in the U.S. is raised on farms in Indonesia, Vietnam, and China.  30% of the world’s production is in Asia, and 54% is in Latin America.  Texas is where most shrimp are farmed in the U.S. The 2 most common species raised are the Pacific white-legged shrimp (Litopannaeus vannamei), and giant tiger prawns (Penneus monodon).  Some claim wild caught shrimp from the Gulf Coast are sweeter, but I think they taste like gasoline because of all the oil spills there.  It takes 3-6 months to raise a shrimp from egg to saleable adult, and shrimp farmers cut off the eye-stalks of the females to increase egg production.

Nile tilapia (O. niloticus).  This was the 2nd most common seafood item I consumed during 2020.

The species of tilapia (Oreochronis sp.) raised by farmers originated in Africa.  5 species of tilapia now live in southeastern North America where they have become an invasive species, but they can’t survive in waters below 50 degrees F and will probably not expand out of the region.  An adult can be raised from a fingerling in 6-7 months on a cereal diet, making them a clean fish to produce.  Indonesia, Egypt, Brazil, and the Phillippines lead world production.  I notice the ones I eat come from Ecuador.

Atlantic salmon came in 3rd.  All salmon sold in grocery stores (even those labeled as wild salmon) are farm-raised.

Norway, Chile, Scotland, and Canada are the leading world producers of salmon, and the vast majority are Atlantic salmon (Salmo samar). There is no such thing as wild caught salmon in grocery stores.  Fish labeled as “wild caught” are actually wild fish driven into pens and fed just like farm-raised salmon.  Trout sold in grocery stores are also farm-raised.

Channel catfish was my 4th most consumed seafood.  This is the only species I ate that mostly originated in the U.S.

In North America channel catfish (Ictalurus punctatus) are raised in the Mississippi Delta (including Mississippi, Alabama, and Arkansas) and California.  Still, the world produces 3 times more catfish than the U.S.  The American catfish lobby legally forced grocery stores into labeling Chinese-raised catfish as basa in order to reduce competition.  How silly?  A consumer purchasing basa is actually buying a species of the shark-finned catfish (Pangasiidae sp.).  1 acre of water can produce 300 pounds of catfish–a more efficient production of protein than any chicken farm or cattle ranch can match.

My consumption of wild caught fish is low, and so is the quantity and quality offered in the average supermarket, probably because the oceans are so overfished. The croaker I ate tasted like fish that had sat on a fish market counter for 3 days before they stuck it in a box and froze it. Tuna was the only significant component of wild caught fish in my tally, but scientists are experimenting with tuna farms.  In the future farm-raised tuna might be found in grocery store fish cases alongside farm-raised shrimp, tilapia, salmon, and catfish.