Fossils

[Flutterby]

Not sure what I'm looking at but interesting.

[Lisbeth]

Looks a bit like marble

[Dzombo]

Not sure what I'm looking at but interesting.

Fossilised leaves

[Flutterby]

[Lisbeth]

Fossil track sites tell the story of ancient crocodiles in southern Africa

March 31, 2020 | Charles Helm, Research Associate, African Centre for Coastal Palaeoscience, Nelson Mandela University


Reptile, avian and mammal tracks and Middle Stone Age artefacts on a large track bearing surface which has since been buried by a landslide. Images modified from Helm, et al. 2020. South African Journal of Science, 116

“The Pleistocene” often evokes images of ice ages – with much of the planet covered by great ice sheets. In reality, this geological epoch that started 2.6 million years ago and lasted until about 11,700 years ago was a time of wildly swinging climatic conditions, typically with long, cold “glacial” phases interspersed with warm “interglacials”.

On the Cape south coast of South Africa, the effects of these changes were dramatic. Sea levels dropped during the “glacials”, exposing the vast Palaeo-Agulhas Plain, and around 91,000 years ago the coastline was as much as 60 km south of its present location. In contrast, during an “interglacial” around 400,000 years ago, sea levels were as much as 13 metres above their present levels. Extensive traditional palaeontological evidence from this region, in the form of body fossils, indicates the existence of a Pleistocene megafauna, some members of which are now extinct.

However, it is becoming evident that this “body fossil record” is not complete. Ichnology – the study of tracks and traces – can complement this record. Fossil tracksites have proven their capacity to teach us the unexpected.

Today the Cape south coast of South Africa contains numerous palaeosurfaces. These rock surfaces are the cemented remains of the dune and beach surfaces that existed when vertebrates, including our Homo sapiens ancestors, were making tracks in the region in the Pleistocene Epoch.

Our research team at the African Centre for Coastal Palaeoscience at Nelson Mandela University has been able to identify more than 250 vertebrate tracksites along a 350kms stretch of the Cape south coast. Together these sites contribute to an ecological census of the diverse fauna that inhabited the coast, and they help in the interpretation of palaeoenvironment. For example, the presence in the region of giraffe and hatchling turtles is only known through our documentation of their trackways. And the early modern human presence is represented not only by tracks but also by evidence of patterns that our ancestors created on surfaces of sand.

Now we can add crocodiles to the list of ancient animals that populated this area during the Pleistocene Epoch. In a paper published in the South African Journal of Science, our team described the tracks and probable swim traces of large reptiles from this coast, from a series of sites within the Garden Route National Park. Swim traces are the traces that a swimming animal makes on the bottom surface of a body of water. Their appearance varies, depending on the water depth and the length of the animal’s limbs; for example, in deep water only faint scrapes may be present where its claws or digits just touch the bottom.

While crocodylian fossil swim traces have been described from other continents, to the best of our knowledge the examples we describe are the first such reptilian swim traces from Africa. One example of hippopotamus swim traces has been reported from Kenya.

Among other benefits, understanding these palaeoenvironments and palaeoclimates (which are relatively recent in ‘geological time’) may help us to better understand our current challenges with climate change.

When large reptiles roamed

Our findings suggest, based on the composition of the rock surfaces, that the tracks and swim traces were made in a lagoon setting. The likelihood is that tracks of both the Nile crocodile (Crocodylus niloticus) and the Water Monitor (Varanus niloticus) are present.

There are no reptiles in the region today that are capable of making such tracks and traces, and there is nothing substantial to suggest their presence on the Cape south coast from the archaeological record or historical records. The current southern range limit of the Nile crocodile is from a site many hundreds of kilometres to the northeast, where a population was introduced.

These findings therefore probably indicate that there was once a more extensive range for the Nile Crocodile and the Water Monitor. Given the ectothermic biological requirements of large reptiles, we can infer a warmer climate, probably during a warm “interglacial”.

Embedded in one of the palaeosurfaces, which contained multiple large reptile trackways, as well as mammal and avian tracks, we found two Middle Stone Age stone artefacts, pictured below. We cannot be certain what they were used for, as we were not permitted to remove them for detailed analysis. But their presence suggests something which had not previously been documented: a spatial and temporal association in this environment between humans and large reptiles, or at least mutual use of habitat. Unfortunately a large landslide has subsequently buried this track-bearing surface.


Middle Stone Age artefacts, scale bars in cm and mm. Authors supplied

Rock samples from these surfaces have been taken for dating. Based on previous dating studies we anticipate that the results are likely to be within the range of 158,000 years to 70,000 years. Obtaining an accurate date would establish the approximate moment in time when these tracks were registered, and would help to corroborate the Middle Stone Age appearance of the stone artefacts.

Deeper understanding

These discoveries illustrate again the potential of ichnology to complement the traditional palaeontology record, and to contribute to the understanding of Pleistocene palaeoenvironments, in an area which is of great importance in the study of modern human origins.

[Lisbeth]

Fossil find suggests Homo erectus emerged 200,000 years earlier than thought

April 3, 2020 | Stephanie Baker
Researcher in Palaeoanthropology, University of Johannesburg - Angeline Leece, Palaeoanthropologist - Jesse Martin, PhD Researcher, La Trobe University - Matthew Caruana, Lecturer in Archaeology, University of Johannesburg- Prof. Andy I.R. Herries, Head of Department of Archaeology and History, La Trobe University - Renaud Joannes-Boyau, Senior research fellow, Southern Cross University


The ~2 Ma Homo erectus cranium, DNH 134, from the Drimolen Fossil Hominin site. Matthew V. Caruana

The human evolutionary path is complicated. It’s almost impossible to say exactly when we modern humans became “us”. This quandary is best articulated by the famous naturalist Charles Darwin in his book The Descent of Man:

- In a series of forms graduating insensibly from some apelike creature to man as he now exists, it would be impossible to fix on any definite point where the term ‘man’ ought to be used.

The understanding of modern humans’ own genus, Homo, has taken many turns over the last century. Homo erectus, one of our purported ancestors, was first discovered in Indonesia in 1891 by geologist and anatomist Eugene Dubois. Since then, representatives of both this species, and other Homo, have been found across the world; for instance, in 2015, a new species of Homo, Homo naledi, was discovered in South Africa. Another new Homo species, Homo luzonensis, was found more recently in the Philippines in 2019.

These discoveries, combined, have led scientists to set Homo erectus‘ emergence at about 1.8 million years ago – with the oldest known record coming from Dmanisi, Georgia and an important slightly later record from the East African Rift valley.

But our new discovery in South Africa’s Cradle of Humankind, which has just been published in Science, suggests that Homo erectus actually emerged 200 000 years earlier than we thought. We were part of a team from South Africa, Australia, Italy and the US that discovered a Homo erectus cranium which has since been dated to almost 2 million years ago.

This is a hugely important find. It reasserts that Homo erectus’ origins are in Africa, not Asia. Our discovery suggests, though, that Homo erectus likely did not evolve in eastern Africa as so often thought but perhaps somewhere else in Africa, or potentially in South Africa itself.

More evidence is needed before firm conclusions can be reached, of course. But the South African find means that the Drimolen fossil site – where we made the discovery – could represent an important shift in the simple narrative that all early species of human ancestry are East African.

A critical discovery

The Drimolen Fossil Hominin site in the Cradle of Humankind, northwest of Johannesburg, has been excavated since its discovery in 1992. The site is best known for its Paranthropus robustus, another ancient hominin species with massive teeth, as well as some early Homo fossils. The most famous specimen from Drimolen is the most complete skull of Paranthropus robustus ever discovered, DNH 7.

It was here that members of our team found the fossil cranium that has been named DNH 134. Its nickname is Simon, named for the site technician whose contribution to the team was immeasurable. Simon Mokobane sadly passed away in 2018, but his expertise, unwavering support and fossil knowledge will forever be remembered.

In 2015, during the Drimolen Field School, a student named Richard Curtis began excavating an intriguing, but highly fragmented specimen. At first, no one was sure what it was from but in-field reconstructions quickly revealed that it was a hominin cranium.

We used a battery of dating methods, including Uranium-lead dating on the flowstones, Uranium-Series Electron Spin Resonance on fossil teeth and Palaeomagnetism on sediments. Each of these complimentary techniques helped to establish a very narrow age of 2.04-1.95 million years for the whole Drimolen Main Quarry and the fossils found in it, including DNH 134.

DNH 134 is extremely significant. Its discovery and dating means that the story of Homo erectus and its journey out of Africa is more complicated than previously thought. Also, we know too that South Africa played a seminal role in this key species that ultimately led to us.

Next steps

Work will continue at the Drimolen site. We aim to continue excavating using a new method where our efforts are focused along the breccia (fossilised rock with fossils in it). This has proved fruitful with not only the discovery of DNH 134, but also a male Paranthropus robustus skull (DNH 152; also discussed in the Science article) as well as a number of other hominin remains we are still studying.

The site also has a wide variety of animal fossils from both extinct and living species, all of whom add to the overall story that we aim to build about how our ancient ancestors lived.

We will also continue to encourage young palaeoanthropologists from across the African continent to get involved in excavations. The site hosts an annual field school with international partner institutes and offers full scholarships exclusively to students from African countries (South Africans have first preference).

The idea behind this is to ensure that researchers from the continent and country are at the forefront of future discoveries that add to the human story.

[Lisbeth]

Who of you, living in Gauteng or visiting often, has not been to " Cradle of Humankind"??

[Flutterby]

I've been.

[Lisbeth]

Good girl

[Richprins]

Is this a fossil?

Given to me as part of a potted plant ensemble 20 years ago. The plants have been dead for 19 years...