Posts Tagged ‘Out of Africarabia’

Ancient Chinese teeth confirm many and older Out of Africa events

October 15, 2015

Over at 6,000 generations I post about the new paper about the 47 human teeth found in Fuyan Cave, Daoxian, China which are between 80,000 and 120,000 years old.

The 47 human teeth found in Fuyan Cave, Daoxian, China. photo S. XING AND X-J. WU via DiscoveryNews

There were clearly many Out of Africa or Africarabia events starting from 130,000 years ago both before and after the Toba explosion.

80,000-120,000 year old modern humans in S China confirm many and older Out of Africa events

The single Out of Africa event for modern humans is clearly far too simplistic. It is also clear that there were many back to Africa movements as well. Humans expanded sometimes because their old habitats were no longer viable. But, it seems, humans also explored and expanded into new territories from regions of plenty and where they maintained some contact with where they had come from. Probably, just because they could.

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Homo erectus was making engravings 500,000 years ago

December 4, 2014

Long before any specimens of Homo sapiens were even gleams in the eyes of their hominin ancestors, Homo erectus peoples on Java (how and when did they get there?) were using shells as tools and were making engravings on the shells themselves. A new paper in Nature reports on studies of hundreds of fossil shells from the Homo erectus site Trinil, on the Indonesian island of Java. The shells are part of the Dubois Collection held at the Naturalis Biodiversity Center in Leiden. They have been dated to about 500,000 years ago.

Of course if all Homo Sapiens came Out of Africa (or Africarabia) around 100,000 years ago, then these Homo erectus on Java must have gone extinct without leaving any survivors (unless some of their genes still live on through later admixtures).

Joordens J.C.A., et al. Homo erectus at Trinil on Java used shells for tool product i on and engraving, Nature 10.1038/nature19362.

The 'Pseudodon shell' fossil with the engraving made by Homo erectus op Trinil. (Photo: Wim Lustenhouwer, Vrije Universiteit)

The ‘Pseudodon shell’ fossil with the engraving made by Homo erectus on Trinil. (Photo: Wim Lustenhouwer, Vrije Universiteit)

From the Leiden University Press Release:

Oldest ever engraving discovered on 500,000-year-old shell

Homo erectus on Java was already using shells of freshwater mussels as tools half a million years ago, and as a ‘canvas’ for an engraving. An international team of researchers, led by Leiden archaeologist José Joordens, published this discovery on 3 December in Nature. The discovery provides new insights into the evolution of human behaviour.

‘Until this discovery, it was assumed that comparable engravings were only made by modern humans – Homo sapiens – in Africa, starting about 100,000 years ago,’ says lead author José Joordens, researcher at the Faculty of Archaeology at Leiden University.

A team of 21 researchers studied hundreds of fossil shells from the Homo erectus site Trinil, on the Indonesian island of Java. The shells are part of the Dubois Collection held at the Naturalis Biodiversity Center in Leiden. The shells were excavated at the end of the 19th century by the Dutch physician and researcher Eugène Dubois, the discoverer ofPithecanthropus erectus – now known as Homo erectus.

The discovery of an engraved geometrical pattern on one of the shells came as a total surprise. The zigzag pattern, that can only be seen with oblique lighting, clearly pre-dates the weathering processes on the shell arising from fossilisation. The study has excluded the possibility that the pattern could have been caused by animals or by natural weathering processes and shows that the zigzag pattern is the work of Homo erectus.

By applying two dating methods, researchers at the VU University Amsterdam and Wageningen University have determined that the shell with the engraving is minimally 430,000 and maximally 540,000 years old.This means that the engraving is at least four times older than the previously oldest known engravings, found in Africa. …..

…… This research has shown that these early human-like people were very clever about how they opened these large freshwater mussels; they drilled a hole through the shell using a sharp object, possibly a shark’s tooth, exactly at the point where the muscle is attached that keeps the shell closed. ‘The precision with which these early humans worked indicates great dexterity and detailed knowledge of mollusc anatomy,’ says Frank Wesselingh, a researcher and expert on fossil shells at Naturalis. The molluscs were eaten and the empty shells were used to manufacture tools, such as knives.

A. Shell tool, made by Homo erectus. B. Detail of the sharp edge used for cutting or etching. (Photo: Francesco d'Errico, Bordeaux University)

A. Shell tool, made by Homo erectus. B. Detail of the sharp edge used for cutting or etching. (Photo: Francesco d’Errico, Bordeaux University)

 

 

Supervolcanos can erupt sponataneously without an external trigger

January 7, 2014

New research suggests that supervolcanos do not need an external trigger to erupt. Bouyancy effects and the magma volume could be sufficient for spontaneous eruption.

Wim J. Malfait, Rita Seifert, Sylvain Petitgirard, Jean-Philippe Perrillat, Mohamed Mezouar, Tsutomu Ota, Eizo Nakamura, Philippe Lerch, Carmen Sanchez-Valle. Supervolcano eruptions driven by melt buoyancy in large silicic magma chambersNature Geoscience, 2014; DOI:10.1038/ngeo2042

From the Press Release:

Scientists have reproduced the conditions inside the magma chamber of a supervolcano to understand what it takes to trigger its explosion. These rare events represent the biggest natural catastrophes on Earth except for the impact of giant meteorites. Using synchrotron X-rays, the scientists established that supervolcano eruptions may occur spontaneously, driven only by magma pressure without the need for an external trigger. The results are published in Nature Geosciences.

A well-known supervolcano eruption occurred 600,000 years ago in Wyoming in the United States, creating a huge crater called a caldera, in the centre of what today is Yellowstone National Park. When the volcano exploded, it ejected more than 1000 km3 of ash and lava into the atmosphere, 100 times more than Mt Pinatubo in the Philippines did in 1992. Big volcanic eruptions have a major impact on the global climate. The Mt Pinatubo eruption decreased the global temperature by 0.4 degrees C for a few months. The predictions for a super volcano are a fall in temperatures by 10 degrees C for 10 years.

Abstract: Super-eruptions that dwarf all historical volcanic episodes in erupted volume and environmental impact are abundant in the geological record. Such eruptions of silica-rich magmas form large calderas. The mechanisms that trigger these super-eruptions are elusive because the processes occurring in conventional volcanic systems cannot simply be scaled up to the much larger magma chambers beneath supervolcanoes. Over-pressurization of the magma reservoir, caused by magma recharge, is a common trigger for smaller eruptions, but is insufficient to generate eruptions from large supervolcano magma chambers. Magma buoyancy can potentially create sufficient overpressure, but the efficiency of this trigger mechanism has not been tested. Here we use synchrotron measurements of X-ray absorption to determine the density of silica-rich magmas at pressures and temperatures of up to 3.6 GPa and 1,950 K, respectively. We combine our results with existing measurements of silica-rich magma density at ambient pressures to show that magma buoyancy can generate an overpressure on the roof of a large supervolcano magma chamber that exceeds the critical overpressure of 10–40 MPa required to induce dyke propagation, even when the magma is undersaturated in volatiles. We conclude that magma buoyancy alone is a viable mechanism to trigger a super-eruption, although magma recharge and mush rejuvenation, volatile saturation or tectonic stress may have been important during specific eruptions.

Supervolcanos do not occur all that often – perhaps one every 50,000 to 100,000 years. When they do occur they devastate a large geographical area and affect the climate for a decade or so. How much destruction of organic life occurs depends on the geographical area affected and the life that is extant there.

New Zealand’s Taupo Volcano was the most recent and erupted about 26,500 years ago. With a VEI of 8, just over 1,000 kmof ash were ejected. Though modern man had reached Australia by then, the effects of this eruption do not seem to have significantly delayed the march of humans. The Toba eruption 74,000 years ago occurred when the total population of all human species (Modern Humans, Neanderthals, Denisovans …..) was between 1 and 10 million. This eruption is also classified as a VEI of 8 and 2,800 km³ of material was ejected. Life was virtually extinguished from India to South East Asia. The effects were devastating not only in the fall out-zone but also – it seems – in hampering the expansion of modern humans out of AfricarabiaThis eruption may thus have caused one of the critical bottlenecks which has determined the subsequent evolution and expansion of humans. 

Image

Toba Fallout (Smithsonian Institute)

While a supervolcano could erupt at any time, it is much more probable to occur than a major asteroid collision with the earth (one in 100,000 years as opposed to once in tens of millions of years). But the volume of magma involved suggests that some early detection (perhaps 5 -10 years) may be possible. For the pressure to build up sufficiently in such a volume a significant bulging of the earth’s crust is likely and should be detectable. But while science fiction can imagine a battery of nuclear warheads to divert an oncoming asteroid in its trajectory, it is difficult to conceive of any way to prevent a supervolcano from erupting. Geo-engineering on a  scale massive enough to relieve some of the pressure in the magma is just conceivable at the edge of fantasy but even that could not prevent the eruption.

Promiscuity in the pleistocene

January 2, 2014

Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology and his colleagues from various institutions are making stunning advances in the analysis of ancient DNA. The complete genome of a Neanderthal has now been reconstructed with a remarkable level of detail.

The complete genome sequence of a Neanderthal from the Altai MountainsKay Prüfer et al, Nature 505, 43–49 (02 January 2014),  doi:10.1038/nature12886

Editors Summary: Recent excavations in the Denisova Cave in the Altai Mountains of southern Siberia have yielded a wealth of hominin fossils from a site that has been occupied for perhaps 250,000 years or more. Now a high-quality genome sequence has been determined from a circa 50,000-year-old toe bone — a proximal toe phalanx — excavated from the east gallery of Denisova Cave in 2010. The sequence is that of a Neanderthal woman whose parents were closely related — perhaps half-siblings or uncle and niece. Such inbreeding was also common among her recent ancestors. Comparisons with other archaic and present-day human genomes reveal several gene-flow events among Neanderthals, the closely related Denisovans and early modern humans, possibly including gene flow into Denisovans from an unknown archaic group. The high-quality Neanderthal genome also helps to establish a definitive list of substitutions that became fixed in modern humans after their separation from the ancestors of Neanderthals and Denisovans.

promiscuity in the pleistocene

But what is also becoming clear is that there were more “species” of homo erectus who existed in parallel than has generally been assumed and also that sexual encounters and interbreeding between these cousin-species has been a regular occurrence over some 250,000 years. And so there have been times when Anatomically Modern Humans (AMH), Neanderthals, Denisovans and the “unknown” hominim have co-existed.

The AMH-Neanderthals split is thought to have occurred about 400,000 years ago. The split with the unknown hominims then must have been around 500,000 years ago. The Denisovans split off from the Neanderthals perhaps about 300,000 years ago. The Out-of-Africa split among AMH was around 100,000 years ago.

A Neanderthal in our time. (copyright Nenderthal Museum / H Neumann)

A Neanderthal in our time. (copyright Nenderthal Museum / H Neumann)

These ancient splits were all probably in and around Africa even if the Out-of-Africa event for AMH is now more likely to have been  many such events and an expansion out of Africarabia. But it also means that a wave of “unknown hominims” split off from the mainline after a mainline group had left Africa and then spread out to unknown areas. Neanderthals probably split from their parent line of descent also outside of Africa but there must first have come a migration from Africa. The Neanderthal-Denisovan split must also have taken place outside of Africa. Clearly there have been many migrations Out of Africa over the last 400,000 years.

Carl Zimmer writes, “Evolution is a mixture of flow–the cascade of genes from parents to offspring, and the criss-cross movement between populations and species”.

But this generates a myriad of new questions. How large were the troops or tribes or clans of these ancient hunter-gatherers that they could sustain such large migrations? For how long and in what proximity did these different species of man co-exist. These troops – it is thought – probably did not number more than about 50. Some critical population would have been required for sufficient interactions to have taken place between the species. At any one time the total human population – of all species – may have approached 10 million (for if this was – say – just 1 million the opportunities to interbreed would not have been many). They all had fire, but did they all have some form of speech?

But most fascinating of all is how the interbreeding took place. Was it just a product of normal rape and pillage? Did violent clashes lead to the victors impregnating the vanquished, or were there other scenarios for individuals to mate? At some point there must have been children who were 50% Neanderthal and 50% AMH. And some who were 50% Neanderthal and 50% Denisovan. How did they survive? What kind of society existed in these ancient times that would permit such offspring not only to survive but also to mate and produce offspring in their turn? But however it happened, our ancestors in the pleistocene were a promiscuous lot.

Could it be that it was only among AMH  – after they had been vanquished and raped and pillaged by Neanderthal raids – that such mixed children were allowed not only to survive but also to thrive?

Migration from India brought genes, tools and dingoes to Australia 4,200 years ago

January 15, 2013

It is generally assumed that the expansion of AMH from Africa (or Africarabia) reached S-E Asia around 70,000 years ago and Australia some 40,000 – 50,000 years ago. The Australian population then remained virtually isolated until quite recently. But a new genome-wide study suggests that there was migration from India to Australia some 4,200 years ago during the Holocene and that they brought stone-tools and the ancestor of the dingo with them. The study suggests that after the first migrants originally arrived in Sahul, the Australian, New Guinea and Mamanwa populations split from each other some 36,000 years ago. But by – an as yet unknown route – migrants from India arrived in Australia between 4,000 and 5,000 years ago.

Though this coincides with the height of the Indus Valley civilization in 2600 BC, I think it is more likely that any ocean-based, island-hopping migration at this time would have started – at least geographically – from S-E India rather than from the Indus Valley civilization in N-W India. But coastal navigation around the Indian coastline of that time would have been well within the capabilities of the Indus valley inhabitants. This is also the period when proto-Dravidian was the language across most of India (including in the Indus valley civilization) and it would be interesting if there are any traces in language which match this genetic data.

Genome-wide data substantiate Holocene gene flow from India to Australia, by Irina Pugach, Frederick Delfin, Ellen Gunnarsdóttir, Manfred Kayser, and Mark Stoneking, Proceedings of the National Academy of Sciences, 

http://www.pnas.org/content/early/2013/01/09/1211927110

Abstract:The Australian continent holds some of the earliest archaeological evidence for the expansion of modern humans out of Africa, with initial occupation at least 40,000 y ago. It is commonly assumed that Australia remained largely isolated following initial colonization, but the genetic history of Australians has not been explored in detail to address this issue. Here, we analyze large-scale genotyping data from aboriginal Australians, New Guineans, island Southeast Asians and Indians. We find an ancient association between Australia, New Guinea, and the Mamanwa (a Negrito group from the Philippines), with divergence times for these groups estimated at 36,000 y ago, and supporting the view that these populations represent the descendants of an early “southern route” migration out of Africa, whereas other populations in the region arrived later by a separate dispersal. We also detect a signal indicative of substantial gene flow between the Indian populations and Australia well before European contact, contrary to the prevailing view that there was no contact between Australia and the rest of the world. We estimate this gene flow to have occurred during the Holocene, 4,230 y ago. This is also approximately when changes in tool technology, food processing, and the dingo appear in the Australian archaeological record, suggesting that these may be related to the migration from India.

BBC reports:

“For a long time, it has been commonly assumed that following the initial colonization, Australia was largely isolated as there wasn’t much evidence of further contact with the outside world,” explained Prof Mark Stoneking, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

“It is one of the first dispersals of modern humans – and it did seem a bit of a conundrum that people who got there this early would have been so isolated.”

To study the early origins of Australia’s population, the team compared genetic material from Aboriginal Australians with DNA from people in New Guinea, South East Asia and India.

By looking at specific locations, called genetic markers, within the DNA sequences, the researchers were able to track the genes to see who was most closely related to whom.

They found an ancient genetic association between New Guineans and Australians, which dates to about 35,000 to 45,000 years ago. At that time, Australia and New Guinea were a single land mass, called Sahul, and this tallies with the period when the first humans arrived.

But the researchers also found a substantial amount of gene flow between India and Australia.

Prof Stoneking said: “We have a pretty clear signal from looking at a large number of genetic markers from all across the genome that there was contact between India and Australia somewhere around 4,000 to 5,000 years ago.”

He said the genetic data could not establish the route the Indians would have taken to reach the continent, but it was evidence that Australia was not as cut off as had been assumed.

“Our results show that there were indeed people that made a genetic contribution to Australians from India,” Prof Stoneking explained.

The researchers also looked at fossils and other archaeological discoveries that date to this period.

They said changes in tool technology and new animals could possibly be attributed to the new migrants.

Prof Stoneking said: “We don’t have direct evidence of any connection, but it strongly suggestive that microliths, dingo and the movement of people were all connected.”

Out of Africarabia

November 9, 2012

There has been a gap of 50-65,000 years between the genetic time-line of the Out-of-Africa theory and archaeological indications of the earlier presence of anatomically modern humans outside of Africa. But the genetic evidence is now going back in time and approaching the archaeological time-line. “Out-of-Africa” is beginning to look much more like “Out-of-Africarabia”.

“Out-of-Africa” is morphing into “Out-of Africarabia” as genetic and archaeological time-lines converge

Out of Africarabia


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