Dating the Toba Eruption.

Sometime between 69 000 and 77 000 years ago a large volcano occupying the site of the current Lake Toba on northern Sumatra underwent what is believed to have been the largest volcanoc eruption of the Quaternary Period, covering much of south Asia in around 15 cm of ash, and probably causing atmospheric effects that resulted in a six year winter and a global downturn in temperatures that lasted about a thousand years. This is widely thought to have had a profound affect on Early Human populations, which were already expanding from Africa into Asia at the time of the eruption, with some palaeoanthropologists linking the event to a (known) bottleneck in Human genetic evolution, when the global human population is believed to have dropped to a few thousand reproducing individuals, and suggesting that the Human population of the time was wiped out apart from a few groups in East Africa. However determining a precise date for the event has proved problematic, with estimates of the timing of the event having margins of error in the thousands of years, which makes it difficult to relate the time of the eruption to archaeological sites, and hard to differentiate the climatic effects from those relating to longer climate cycles.

In a paper published in the Proceedings of the National Academy of Sciences of the USA on 29 October 2012, Michael Storey of the Quaternary Dating Laboratory at the Department of Environmental, Social and Spatial Change at Roskilde University, Richard Roberts of the Centre for Archaeological Science at the School of Earth and Environmental Sciences at the University of Wollongong and Mokhtar Saidin of the Centre for Global Archaeological Research at the Universiti Sains Malaysia, describe the results of a study of ash deposits linked to the Toba eruption at Lenggong Valley in Peninsular Malaysia, roughly 400 km to the northeast of the eruption site.

Location of the Toba caldera, north Sumatra, and Lenggong, Perak (LP), Malaysia, site of the borehole. Six kilometers to the south of the Lenggong borehole is the archaeological site at Kota Tampan (KT) located on an ancient terrace of the Perak River, where ash occurs between and above stone tools. (Inset) Star on the world map marks the location of the Toba caldera, and the dashed line encompasses presently known occurrences of ash. Story et al. (2012).

Storey et al. used Argon-Argon isotope dating to determine the age of the ash deposits. This relies on determining the ratio of radioactive Argon⁴⁰ to non-radioactive Argon³⁹ within minerals from igneous or metamorphic rock (in this case volcanic ash) to determine how long ago the mineral cooled sufficiently to crystalize. The ratio of Argon⁴⁰ to Argon³⁹ is constant in the atmosphere, and this ratio will be preserved in a mineral at the time of crystallization. No further Argon³⁹ will enter the mineral from this point, but Argon⁴⁰ is produced by the decay of radioactive Potassium⁴⁰, and increases in the mineral at a steady rate, providing a clock which can be used to date the mineral.

Using this method they were able to determine an age of 73 880 years, give-or-take 320 years, for the ash sample, a date an order of magnitude more accurate than any such date achieved for the Toba Eruption to date.

Storey et al. also not that at the nearby Kota Tampan site the ash deposits lie directly on top of archaeological artifacts consistent with the work of Early Modern Humans on an ancient terrace of the Perak River. This suggests that Early Modern Humans had reached this area by ~74 000 years ago, which is consistent with other remains thought to have been produced by Early Modern Humans and found at Jwalapuram in southern India, which date from around 78 000 years ago. However it cannot be determined if the toolmakers were able to survive the Toba Eruption, or whether they are ancestral to modern Human populations in east Asia or Australasia. Furthermore it is possible that the toolmakers were Denisovans, members of an archaic Human group known from Siberia, who are believed to have shared a non-African ancestor with the Neanderthals (i.e. to have been living outside Africa long before 74 000 years ago). To complicate matters further some palaeoanthropologists believe that the Denisovans may be among the ancestors of the Melanesians and Aboriginal Australians.

See also The spread of deserts in northern China, Toolmaking in the northeastern Thar Desert 95 600 years ago, Eruptions on Barren Island, Eruption on Mount Marapi, Sumatra and Eruptions on Krakatau.

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Toolmaking in the northeastern Thar Desert 95 600 years ago.

The Thar Desert covers over  200,000 km² of land in the northwest part of the Indian Subcontinent, straddling the border between Pakistan and India. It marks the boundary between the deserts of North Africa and the Middle East to the west and the Oriental Biogeographical Zone to the east, and thus marks an important milestone in the movement of early humans (and other hominids) from Africa into south and east Asia.

In a paper published in the journal Quaternary Science Reviews on 1 October 2013, James Blinkhorn of the Centre de la Préhistoire à l'Actuel: Culture, Environnement et Anthropologie at Université Bordeaux, Hema Achyuthan of the Department of Geology at Anna University and Michael Petraglia and Peter Ditchfield of the Research Laboratory for Archaeology and the History of Art at the School of Archaeology at Oxford University describe a collection of Middle Palaeolithic artifacts from at
Katoati in the northeastern Thar Desert, dated to between 12 000 and 95 600 years ago.

The location of the Katoati site, as well as other similar sites in India and the Middle East. Blinkhorn et al. (2013).

Blinkhorn et al. describe the discovery of a number of stone artifacts resembling Middle Paleaolithic artifacts from Nubia, the eastern Sahara, souther Arabia and south India. The oldest of these artifacts considerably predate the oldest known previous material from the Thar Desert, which is around 60 000 years old, and the oldest previously known material from India, artifacts from Jwalapuram in southern India which date from around 78 000 years ago, strongly supporting the idea that early humans reached India via the Thar Desert rather than by another route. Furthermore maintain the same culture across the time of the Toba Eruption of about 75 000 years ago, which is theorized to have drastically reduced human numbers in the Late Pleistocene to only a few thousand individuals, suggesting that early humans in this area were able to survive this event.

(1) Tanged point (projectile tip) from Jwalapuram in southern India. (2 & 3) Tanged point from Katoati; (2) line drawing and (3) photograph. Blinkhorn et al. (2013).

The objects were buried in fluvial deposits (riverbeds) over a long period of time, with sand dune formation between them, suggesting the rivers either meandered or were not a permanent feature. They were apparently found close to where they had been made; all bar one appeared to be made from local rock; quartz, chert and sandstone. The vegetation during the period appears to have been dominated by C4 plants, suggesting an arid, subtropical grassland.

See also The earliest evidence of fire use from million year old sediments in Wonderwerk Cave, Northern Cape Province? Trying to find Peking Man, Pleistocene rock carving from Brazil; possibly the oldest art in the Americas, 20 000 year old stone huts from Kharaneh in Eastern Jordan and Fishermen targeting tuna in East Timor at least 42 000 years ago.

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Another look at the Canteen Kopje Skull.

The Canteen Kopje Skull was unearthed in 1929, by a prospector named Kenneth Kemp, who was sifting the Vaal River gravels for diamonds at Klipdrift in Northern Cape Province, South Africa (river gravels are a good place to look for diamonds, since erosional processes that destroy less durable minerals can concentrate them relative to their original deposits). It made its way to the McGregor Museum in Kimberly, where it was described in a paper in the journal Nature by Robert Broom, the Keeper of Vertebrate Palaeontology at the South African Museum in Cape Town.

A modern visitor posses with the Canteen Kopje Skull. Tripadvisor.

Broom described the skull as being of great antiquity, due to its heavy mineralization. He furthermore noted that it lacked a lower jaw or teeth, a sign, he felt, that it was not a burial, but a skull that had been interred in the Vaal River deposits by natural means, though he noted the presence of 'limb bones' which would be highly unlikely (from the viewpoint of a 21st century palaeontologist) to survive natural interment in a fast moving river environment (sluggish rivers do not shift gravel), or reworking from a more stable environment. The gravels at the Canteen Kopje sight are thought to be Late Pliocene to Pleistocene in age, and have not yielded any other bones. At the time interest in the study of early man in South Africa was growing, and the skull was assigned to a race of humans known as Boskop Man, that were then thought to have roamed pre-historic South Africa, but are now regarded as mythical; the bones assigned to Boskop Man are slowly being re-assigned to other human groups.

In a paper published in the South African Journal of Science on 16 January 2012, a team of scientists led by Patricia Smith of the the Laboratory of Biological Anthropology and Ancient DNA at the Hadassah Faculty of Dental Medicine at the The Hebrew University of Jerusalem describe a re-examination of the Canteen Kopje Skull, and the conclusions drawn from it.

Smith et al. examined the current setting of the Canteen Kopje Skull, which has been set into a plaster reconstruction of Boskop Man, and coated with (now chipped and discoloured) shellac, and came to the conclusion that it would not be possible to remove the skull fragments from the plaster matrix without risking damage to the delicate skull. They also noted that the skull showed signs of having received a fairly serious injury in life, but had apparently recovered, something that Broom apparently overlooked.

The Canteen Kopje Skull, as reassembled by Robert Broom. Arrow points to the healed injury. From Smith et al. (2012).

Faced with this problem Smith et al. decided to examine the skull via computerized X-ray tomography (CT scans). Based upon these scans they could find nothing to distinguish the Canteen Kopje Skull from other modern, pre-European skulls, and conclude that the skull is probably of no great antiquity. The skull has undergone some re-mineralization, but it is now understood that this can be a quite rapid process, indeed modern palaeontologists generally suspect that most preserved bones are re-mineralized quite soon after burial, with bones that do not undergo this process decaying within a few years.

3D tomogram reconstructions of the Canteen Kopje Skull, the curly object inside the skull is a bent metal bar supporting the plaster matrix. From Smith et al. (2012)

See also Neanderthals using red ochre at least 200 000 years ago, Fishermen targeting tuna in East Timor at least 42 000 years ago, A re-evaluation of the Iwo Eleru skull, Ancient Ape Skull found in Uganda and Rock Carving on the Gower Peninsula; Britain's oldest art?

Fishermen targeting tuna in East Timor at least 42 000 years ago.

The Jerimalai Rock Shelter was first uncovered in 2005, on a limestone terrace (flat area of limestone) at the eastern tip of East Timor. It was occupied by anatomically modern humans from about 42 000 years ago until about 2500 years ago. The site has previously been noted for its striking obsidian artifacts; archaeologists are uncertain of the source of this obsidian, which has not been found on Timor, implying it may have been traded from further away. Other sites in the area have yielded similar tools, as well as spectacular stone carvings, shards of pottery and signs of animal domestication.

The Jerimalai Rock Shelter.

The 25 November 2011 edition of the journal Science contains a paper by a team lead by Sue O'Connor of the Department of Archaeology and Natural History at the Australian National University which describes the discovery of the remains of large pelagic (ocean going) fish including tuna, as well as the oldest known fish-hooks to have been discovered anywhere in the world. These hooks were made from shell. It is not clear if the hooks were used to catch the tuna, or whether they were caught in another way (such as netting them at they passed through a narrow channel), but either way catching such fish shows a remarkable level of skill and technological achievement for such an early period; these remains are roughly ten times as old as the Egyptian pyramids or Stonehenge, from a time when Europe was still locked in an Ice Age.

The July 2011 edition of the journal Archaeology in Oceania contained a paper by a team lead by Christian Reepmeyer, also of the Australian National University, detailing the extent of obsidian tool use in at Jerimalai and other sites in East Timor and Indonesia. This suggested that all the obsidian found at different locations in East Timor was from a single source, but was unable to locate the source of this material, nor establish if it came from East Timor or further afield. Obsidian is a glassy rock formed by the rapid cooling of rhyolitic lavas at the surface. As such it is seldom found in large deposits, so it is possible that the source was exhausted.

Sites in East Timor and the surrounding islands where sophisticated obsidian tools have been found.

In 2010 a paper by Sue O'connor in the journal Antiquity detailed the discovery of sophisticated rock art at Lene Hara on the north coast of East Timor, which bore a strong resemblance to rock art in Australia.

Rock carving at Lene Hara.

We have known for a long time that early humans in this part of the world had good seagoing skills, since they reached Australia approximately 50 000 years ago, but until fairly recently these people were still widely looked upon as 'primitive'. The picture now emerging from Jerimalai, and other sites on East Timor, and across Indonesia and the islands of Oceania is of a remarkably sophisticated civilization, trading widely and achieving technological feats that would not be matched in other parts of the globe for many millennia.

What is particularly remarkable about the East Timor sites is their proximity to the Island of Flores, where an entirely separate species of human, the diminutive, Homo floresiensis, is thought to have survived till as recently as 19 000 years ago. This would make the fishermen and mariners of ancient Timor and other islands the most advanced culture known to have lived in close proximity to another species of human, though they were clearly active explorers with an impressive array of complex hunting tools.

See also Out of Africa(?) and Mammals on Sciency Thoughts YouTube.

A re-evaluation of the Iwo Eleru skull.

Iwo Eleru is an archaeological site in southeast Nigeria, which comprised a rock shelter containing a number of stone tools and a single human skeleton. It was excavated in 1965 by a team lead by Thorstan Shaw of the University of Ibadan. The findings were published in 1971 in a paper in the journal Man (since 1995 replaced by The Journal of the Royal Anthropological Institute) by Don Brothwell of the Natural History Museum and Shaw. The initial study made morphometric analysis of the skull which suggested that Iwo Eleru man was similar to modern West Africans, but with some archaic features. Morphometric analysis is a method by which a large number of measurements are taken of a fossil, then compared to similar fossils within the same group in order to determine affinities. A radio-carbon date was established for charcoal associated with the skeleton, which gave a age of approximately 13 000 years.

The location of Iwo Eleru and the reconstructed skull.

This month a team lead by Katerina Harvati of the Senckenberg Center for Human Evolution and Paleoecology, Eberhard Karls Universität Tübingen published a paper in the journal PLoS One in which they re-examine the Iwo Eleru skull and provide a new morphometric analysis based upon digital measurements of the skull (the original study used calipers, the best technology available at the time) and a uranium-thorium date for the site.

Despite the extensive studies that have been made of the origins of humanity in Africa, comparatively little is known about human populations there during the Late Pleistocene, and even less for West Africa. For the purpose of the study the Iwo Eleru skull has been compared to a number of neanderthal, Homo heidelbergensis, Homo erectus, modern and other Pleistocene African and Near Eastern skulls. The other African and Near Eastern Pleistocene skulls were the two skulls from Jebel Irhoud in Morocco, currently dated at 160 000 years old, the Ngaloba skull from Laetoli in Tanzania, currently dated at 120 000 years old, two skulls from Qafzeh in Israel, currently dated at between 80 000 and 120 000 years old, the Singa skull from Jebel Irhoud in eastern Sudan, currently dated at between 87 000 and 127 000 and the Skhul skull from Mount Carmel in Israel, currently dated at 100 000 years old.

The morphometric analysis produced by Harvati et al. produced to distinct groups of skulls, one containing the archaic humans (neanderthals, Homo heidelbergensis, Homo erectus) and one containing the modern humans, with some of the Pleistocene African and Near Eastern skulls falling into these groups and some intermediate.

One of the Qafzeh skulls fell consistently within the archaic group, and the Skhul skull was consistently either in or close to this group (more than one analysis was run, since none of these skulls is complete). The other skulls were, depending on the analysis, either in or close to the modern set, or intermediate between the two - with the exception of Iwo Eleru, which was consistently intermediate between the two groups.

This suggests that Iwo Eleru is not a fully modern human, and that therefore more archaic humans can be thought to have persisted in West Africa later than was previously thought. However Harvati et al. do not consider Iwo Eleru to be distinctive enough to classify it as a separate species, preferring to consider it to be an archaic form of modern human (Homo sapiens).

Until comparatively recently the idea of archaic humans surviving as recently as the Late Pleistocene would have been highly controversial. However the recent discoveries of Homo floresiensis in 2003, a distinct species of humans that survived as recently as 13 000 years ago on Flores Island in Indonesia and the Denisovan people in 2010, a species of human living in Siberia around 40 000 years ago, make this rather less surprising. Instead this extends our knowledge of archaic human forms that lived alongside us until quite recently into a new area.

The skull of Homo floresiensis, a 1.1 m hominid from Indonesia.

The Uranium-thorium date established for the bones gave an age of between 11 700 and 16 300 years old, consistent with the original dating.

See also Ancient Ape skull found in Uganda, Rock carving on the Gower Peninsula, Out of Africa(?) and Mammals on Sciency Thoughts YouTube.