The Monitoring Well, Reflections on Geology & Society

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March 20, 2023

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Before going onto looking at Pleistocene fossils from Africa and South America, let’s look at some news items that I thought were interesting.

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March 20, 2023

Life in the Pleistocene: Africa and South America

We’re going to windup our look at fossils from the Pleistocene Epoch with a look at a few examples from the Afrotropical (Africa) and Neotropical Eco-zones. These two eco-zones share a similar array of local climates and ecosystems, so we may see some examples of parallel evolution.

The Afrotropical Eco-zone in the Pleistocene

Figure 1 – The Afrotropic Eco-zones
Credit: carol, Creative Commons Attribution-Share Alike 3.0 Unported license

The Afrotropic Eco-zone includes Sub-Saharan Africa Desert, the southern part of the Arabian Peninsula, Madagascar, a small part of southern Iran and southwestern Pakistan, together with the islands of the western Indian Ocean. During the Pleistocene, it was the home to a huge variety of animals, we’ll take a look a few of them.

Homo erectus

Figure 2 – Homo Erectus Skull in the American Museum of Natural History, New York
Credit: Cathrotterdam, Creative Commons Attribution-Share Alike 4.0 International license

For most of the Pleistocene, one of the most common hominin was Homo erectus. A very successful creature, Homo erectusfirst appeared in Africa around 2 million years ago, probably evolving from an earlier hominin, Homo habilus. Homo erectus not only expanded throughout Africa but was the first hominin to expand its range into Eurasia and Southeast Asia. The youngest fossils of Homo erectus came from Java in Indonesia, from about 117,000–108,000 years ago.

Figure 3 – Hominin Evolution according to Stringer, 2012Credit: Conquistador and Dbachmann, Creative Commons Attribution-Share Alike 4.0 International license

Homo erectus didn’t die without issue. Among the descendants of Homo erectuswere the Indonesian hobbit, H. floresiensis, Homo antecessor, Homo heidelbergensis, Homo neanderthalensis, Homo denisovaand ourselves, Homo sapiens. The descent is not a straight line, but is marked by lots of migrations and intermingling of previously separate populations as suggested by Figure 3, above.

From the neck down, Homo erectusappears to be indistinguishable from modern humans. In height and weight the fossils show a lot of variation, ranging from 146–185 cm in height and 40–68 kg in weight. This variation seems to have been the result of natural selection acting on separate populations, a phenomena called phenotypic plasticity. The main difference between Homo erectus and ourselves is in the shape of the skull and the size of the brain. Homo erectusbrains varied in size from 546–1,251 cc compared to between 1,000 and 1,600cc for modern humans.

Throughout its range, Homo erectusseems to have been an apex predator eating a wide variety of animals. Also, they used fire and made stone tools, creating the Acheulean stone tool industry.

Figure 4 – Model of Homo erectus man in the Naturhistorisches Museum, WienCredit: Jakub Hałun, Creative Commons Attribution-Share Alike 4.0 International license

Dutch scientist Eugène Dubois discovered the first fossils of Homo erectus in 1891, calling it Pithecanthropus erectus in 1895, also called Java Man. Later discoveries in Java (Solo Man) and China (Peking Man) led Ernst Mayr to combine the species into one: Homo erectus. Later discoveries in Africa and Europe have also been added into the classification Homo erectus.

A long lived species like Homo erectus evolved into a variety of subspecies, these include:

The Swedish naturalist coined the name for the genus Homo in 1758. There is one extant species of Homo, H. sapiens (us) and about 12 extinct species.

Lycaon sekowei

Figure 5 – Bones of Lycaon sekowei
Credit: Cradle of Humankind, Creative Commons Attribution 2.0 Generic license

Human ancestors living during the Pleistocene were not only predators, but also prey. Among the predators that probably fed on hominins were African Wild Dogs, the ancestor of which was Lycaon sekowei. Fossils of Lycaon sekowei have been found in Pliocene to Pleistocene deposits in South Africa as well as Quaternary deposits in Congo-Kinshasa, Kenya, Morocco, and Tanzania.

Lycaon sekowei was a hypercarnivore, that is, its diet was almost exclusively meat. Like modern African Wild Dogs, Lycaon sekowei probably hunted in packs. However, it’s paws appear not to be adapted for running, so it probably didn’t run down its prey, like its modern descendants. Rather, it probably used more direct ambush techniques. If you were a Homo erectus out by yourself, looking for something to eat, you might suddenly find yourself surrounded by a pack of these hypercarnivores and torn to pieces to feed their ravenous appetites.

Figure 6 – African Wild dogs Feeding
Credit: Brian Gratwicke, Creative Commons Attribution 2.0 Generic license

In their 2015 paper, Adam Hartstone-Rose, Lars Werdelin, Darryl J. De Ruiter, Lee R. Berger and Steven E. Churchill were the first to describe Lycaon sekowei in the scientific literature.

British naturalist Joshua Brookes first defined the genus, Lycaon, in 1827. The genus name, Lycaon, was derived from a nasty character in Greek mythology who Zeus turned into a wolf in retribution for Lycaon cooking up one of his sons as a feast for Zeus.

Syncerus antiquus

Figure 7 – Syncerus antiquus skull in the Nairobi National MuseumCredit: Bjørn Christian Tørrissen, Creative Commons Attribution-Share Alike 3.0 Unported license

Also called Pelorovis antiquus, Syncerus antiquus was an African buffalo. Fossils of Syncerus antiquus have been found in Pliocene deposits in South Africa and Quaternary deposits in Congo-Kinshasa, Kenya, Morocco, South Africa, and Tanzania.

Like modern buffaloes, and other bovines, Syncerus antiquus was a herbivore that lived in herds. It was one of the largest bovines that have lived. Up to 3 m in length from muzzle to the end of the tail, the distance between the tips of its horns was as much as 2.4 m and it probably weighed about 1,200 kg although the largest males could have weighed up to 2,000 kg.

Figure 8 – Rock Art from Tin Taghirt on the Tassili n’Ajjer in southern AlgeriaCredit: Linus Wolf, Creative Commons Attribution-Share Alike
3.0 Unported, 2.5 Generic, 2.0 Generic, and 1.0 Generic license

Humans first depicted bovines that looked like Syncerus antiquus in rock art from the Late Pleistocene. In 1851, French zoologist Georges Louis Duvernoywas the first to describeSyncerus antiquus in the scientific literature. British naturalist Brian Houghton Hodgson first described the genus Syncerus in 1847. There is one living species in the genus, S. caffer and two extinct species S. acoelotus, and S. antiquus.

The Neotropic Eco-zone in the Pleistocene

Figure 9 – The Neotropic Eco-zone
Credit: carol, Creative Commons Attribution-Share Alike 3.0 Unported license

The Neotropic Eco-zone covers all of South America together with Central America, the Caribbean islands, parts of Mexico as well as southern Florida in the United States. Let’s look at some of the Pleistocene fossils from that eco-zone.

Doedicurus clavicaudatus

Figure 10 – Skull of Doedicurus clavicaudatus
Credit: Richard Lydekker, public domain

Distantly related to modern armadillos, Doedicurus clavicaudatus was a glyptodont that lived during the Pleistocene of Argentina, Brazil, and Uruguay. It persisted in South America until about 8,000–7,000 years ago. A large herbivore, Doedicurus clavicaudatus weighed about 1,400 kg and sported at spiked 40 kg club on its tail. This did not deter humans, who apparently hunted the animal, possibly to extinction.

Figure 11 – Reconstruction of Doedicurus clavicaudatus
Credit: Nobu Tamura, Creative Commons Attribution-Share Alike 3.0 Unported license

English naturalist Richard Owen, first described Doedicurus clavicaudatusin 1847, originally calling it Glyptodon clavicaudatus. In 1874, German-Argentine zoologist Hermann Burmeister placed it in the genus Doedicurus,of which D. clavicaudatus is the only species.

Mixotoxodon

Figure 12 – Mixotoxodon skull reconstruction
Credit: Rextron, Creative Commons Attribution-Share Alike 3.0 Unported license

A genus of notoungulate, a group of mammals unique to South America, Mixotoxodon lived during the Pleistocene, from about 1,800,000 to 12,000 years ago. Fossils of Mixotoxodon have been found in Argentina, Bolivia, Colombia, Costa Rica, El Salvador, Honduras, Mexico, Nicaragua, Panama, the United States (Texas), and Venezuela. A herbivore, Mixotoxodon was one of the largest notoungulates, weighing of up to 3.8 tonnes, about the size of a modern rhinoceros.

Figure 13 – Mixotoxodon
Credit: Sergiodlarosa, Creative Commons Attribution-Share Alike 3.0 Unported license

American paleontologists Richard van Frank and George Gaylord Simpson first described Mixotoxodon in 1957 from fossils that they found in Venezuela. There is only one species in the genus: M. larensis.

Dusicyon avus

Figure 14 – Dusicyon avus
Credit: Juandertal, Creative Commons Attribution-Share Alike 4.0 International license

About the size of a modern German Shepard dog, Dusicyon avus was a medium sized canid that lived from the Pleistocene until approximately 1000 years ago. A closely related species, Dusicyon australis, lived on the Falkland Islands until about 400 years ago. Fossils of Dusicyon avus have been found in Argentina, Brazil, Chile, and Uruguay.

Figure 15 – Dusicyon australis, the Falkland Islands Fox
Credit: John Gerrard Keulemans, public domain

Hermann Burmeister first described Dusicyon avus in the scientific literature in 1866 in the Annals of the Buenos Aires Museum. His work was later reprinted in 1871 in the English publication, Nature. The genus Dusicyon was first described by the English naturalist Charles Hamilton Smith in 1839, who called it a variety of Canis. In 1914, Oldfield Thomas established the genus. There are three species in the genus: D. avus, D. australis and D. cultridens.

That wraps things up for the Pleistocene. Next week we’ll get to work on the current epoch, the Holocene.

Standard Caveat

The purpose of my weblog postings is to spark people's curiosity in geology. Don't entirely believe me until you've done your own research and checked the evidence. If I have sparked your curiosity in the subject of this posting, follow up with some of the links provided here. If you want to, go out into the field and examine some rocks on your own with the help of a good field guide. Follow the evidence and make up your own mind.

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