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Category Archives: climate

Echoes from the past (May-9-2013)

I am getting updated with a rather long backlog, so I will speed things up placing here in nearly telegraphic style the informative snippets that require less work. This does not mean that they are less interesting, not at all, just that I have to adapt to that elusive quality of time…

Middle Paleolithic

Toba supervolcano only had short-term climate effectBBC.
Research on Lake Malawi’s sediments shows that the climate-change effect of the catastrophic eruption was limited. Droughts previously believed to be from that period have been revised to be from at least 10,000 years before, corresponding to the end of the Abbassia Pluvial rather than to Toba super-eruption.

Upper Paleolithic

Altai rock art and early astronomy from 16,000 BPSiberian Times, Daily Mail.
Sunduki (Khakassia), here there are what are surely the oldest rock art of Northern Asia, representing people hunting or interacting among them, which are from just centuries ago, however other petroglyphs are apparently much older like this horse:

Prof. Vitaly Larichev (Institute of Archeology and Ethnography, Russian Academy of Sciences) has detected a whole astronomical structure implemented in the landscape.

He claims to have found ‘numerous ancient solar and lunar observatories around Sunduki’.

‘This square pattern of stones on the ground shows you the place’, he
told visiting author Kira Van Deusen. ‘I knew there would be an
orientation point, but we had to search through the grass for a long
time to find it.

‘Now look up to the top of that ridge. You see a place where there is
a crack between the rocks? If you were here on the summer solstice, you
would see the sun rise right there. Or you would if you were here 2,000
years so. Now the timing is slightly differen’.



High on one cliff wall is a rock engraving showing dragon heads in one direction, and snake heads in the other.

‘If the sun were shining, we could tell the time,’ he said. ‘In the
morning the shadow moves along the snake’s body from his head to his
tail, and in the afternoon it comes from the other direction along the
dragon.

‘From the same observation point you can determine true north and south by sighting along the mountains’.

Neolithic

Vietnam: early cemetery dug in Thahn HoaAustralian National University.
Some 140 human remains of all ages have been unearthed at the site of Con Co Ngua, estimated to be 6-4000 years old. Cemeteries of this size and age were previously unknown in the region. The site has also revealed a dearth of artifacts. 
The people were buried in fetal position with meat cuts of buffalo or deer.

Chalcolithic

India: 4000 y.o. stone tools unearthed in Bhopal (Madhya Pradesh, Narmada river)India Today.
Details:
  • Some of them are decorated with aquatic animals.
  • 150×200 m. mound in Birjakhedi
  • Terracotta game pieces
  • Pottery (incl. jars, pots, dishes)
  • Stone and ivory beads
Bell Beaker rich lady’s burial unearthed in Berkshire (England)Wessex Archaeology.
The middle-aged woman wore a necklace of tubular golden beads, amber buttons on her clothes and a possible lignite bracelet. She was accompanied by a bell-shaped beaker of the “corded” type (oldest and roughest variant, of likely Central European inception).
The chemical signature of the gold beads is coherent with deposits from Southern Britain and SE Ireland. 

Giza pyramid construction’s logistics revealed Live Science.


Caesar beat the Gauls.
Was there not even a cook in his army?

Bertolt Brecht (A Worker reads History)

Now we know that at the very least the famed early pharaohs Khafra, Khufu and Menkaure, who ordered the massive pyramids of Giza to be built as their tombs did have some cooks in charge of feeding the many workers who actually built them, stone by stone. 
These workers were housed in a village some 400 meters south of the Sphinx, known as Heit el-Ghurab. In this place archaeologists have found a cemetery, a corral with apparent slaughter areas and piles of animal bones. Based on these, researchers estimate that more than 2,000 kilograms of meat were eaten every day during the construction of Menkaure’s pyramid, the last and smallest one of the three geometric mounds. 
The figures estimated for such a logistic operation border disbelief: 22,000 cows, 55,000 sheep and goats, 1200 km² of grazing land (roughly the size of Los Angeles or 5% of the Nile Delta), some 3500 herders (adding up to almost 20,000 people if we include their families). 
A curious detail is that most of the beef was destined to the building of the overseers, while the common workers were mostly fed sheep or goat instead. Another settlement to the East of apparently local farmers ate most of the pork. There were also temporary tent camps closer to the pyramids.

Iron Age

Late Indus Valley Civilization was overcome by violenceNational Geographic.

Harappa (CC by Shephali11011)
The Late Indus Valley Civilization (Cemetery H cultural layer, usually attributed to the Indoeuropean invasions) was, unlike in previous periods, quite violent, new evidence highlights. 
The evidence from the bones also highlights the arrival of many non-local men, who apparently married local women. But the most shocking element is the striking evidence of widespread violence:

The skull of a child between four and six years old was
cracked and crushed by blows from a club-like weapon. An adult woman was
beaten so badly—with extreme force, according to researchers—that her
skull caved in. A middle-aged man had a broken nose as well as damage
to his forehead inflicted by a sharp-edged, heavy implement.
Of the 18 skulls examined from this time period, nearly half showed serious injuries from violence …

Gaming pieces of Melton Mowbray (England)Science Daily.

Excavation of a hillfort at Burrough Hill revealed ancient gaming pieces, among other materials. 

Funerary chamber found near the original location of the Lady of Baza (Andalusia)Paleorama[es].

(CC by P.A. Salguero Quiles)
The tomb has an access gate and is estimated to be from the 5th or 4th centuries BCE (Iberian culture) and, unlike most burials of the time, the corpse was not incinerated. 
The finding highlights the need for further archaeological work in all the hill but the severe budgetary cuts threaten this development. 
Baza (Granada) hosts a dedicated archaeological museum inaugurated in 2011. 

Tocharian mummy buried with marijuana hoardPaleorama[es].

Some 800 grams of the psychedelic plant, including seeds, were found at the burial place of a Tocharian man, presumably a shaman, at Yanghai (Uyghuristan), belonging to the Gushi culture and dated to at least 2700 years ago. The plant belongs to a cultivated variety.
Some of the oldest cannabis evidence are also from that area (Pazyrk culture c. 2500 years ago) and also from Nepal (Mustang, similar dates). Later in Southern Central Asia it was used in combination with opium and ephedra, from where soon migrated to South Asia and many other parts of Eurasia.

Genetics

New device radically reduces costs and time in DNA extractionScience Daily.
Researchers from the University of Washington and NanoFacture Inc. have developed a device, which looks like a kitchen appliance, able to extract DNA from tissues (like saliva or blood) in minutes at low cost and without using the toxic chemicals habitual in the field.
The prototype is designed for four samples but can be scaled for the lab standard of 96 samples at once.

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Sahara 5000 years ago: from grassland to desert in no time

Saharan dust storm blowing into the Ocean (NASA)
Live science reports about a new study, to be published in the Earth and Planetary Science Letters journal, that concludes, based on the dust sediments in the Atlantic Ocean, that the change from grassland to desert of the Sahara some 5000 years ago was very quick. 
In the wet period, known as Neolithic Semi-Pluvial, the dust accumulated in oceanic sediments was only 20% of present day. But that changed very fast around 5000 BP. 
Not many details are provided however.
 
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Posted by on April 13, 2013 in Africa, Chalcolithic, climate, Neolithic, Sahara

 

Atlantic thermohaline currents nearly stopped in some cold spells of the Ice Age

That is what researchers claim in a new study:
Stephan P. Ritz et al., Estimated strength of the Atlantic overturning circulation during the last deglaciation. Nature Geoscience 2013. Pay per viewLINK [doi:10.1038/ngeo1723]

Abstract


The Atlantic meridional overturning circulation affects the latitudinal distribution of heat, and is a key component of the climate system. Proxy reconstructions, based on sedimentary 231Pa/230Th ratios and the difference between surface- and deep-water radiocarbon ages, indicate that during the last glacial period, the overturning circulation was reduced during millennial-scale periods of cooling. However, much debate exists over the robustness of these proxies. Here we combine proxy reconstructions of sea surface and air temperatures and a global climate model to quantitatively estimate changes in the strength of the Atlantic meridional overturning circulation during the last glacial period. We find that, relative to the Last Glacial Maximum, the overturning circulation was reduced by approximately 14 Sv during the cold Heinrich event 1. During the Younger Dryas cold event, the overturning circulation was reduced by approximately 12 Sv, relative to the preceding warm interval. These changes are consistent with qualitative estimates of the overturning circulation from sedimentary 231Pa/230Th ratios. In addition, we find that the strength of the overturning circulation during the Last Glacial Maximum and the Holocene epoch are indistinguishable within the uncertainty of the reconstruction.

Summary of thermohaline circulation (public domain, NASA)
In the North Atlantic the best known thermohaline current is the Gulf Stream, which effectively keeps Europe several degrees warmer than it would be otherwise, allowing a relatively dense population at latitudes unheard of elsewhere on Earth. This current was weak at best in the Ice Age. 
Notice that they say that they can find any difference between present day (Holocene epoch) and the Last Glacial Maximum, so it cannot be inferred, it seems, that the glaciation itself had anything to do with the thermohaline currents but only with  some particular cold spells of the late Upper Pleistocene, particularly the HE1 (c. 18-14.6 Ka ago) and the Younger Dryas (c. 10 Ka ago).
 
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Posted by on February 11, 2013 in climate, Epipaleolithic, Ice Age, Magdalenian, sea

 

"Megadrought" may have affected NW Australia some 5500 years ago

Depictions of the Wondjina rain spirits
(CC by Whinging Pom)
Researchers have detected an apparent “megadrought” affecting at least the region of Kimberley (NW Australia), which hosts some of the most important collections of Aboriginal rock art and may have been one of the first inhabited regions of the island-continent.
The drought may explain a change in artistic style between the Gwion (or Bradshaw) style and the Wondjina one, more modern. Memory of the drought persists in the legends from the Dream Time of the Aboriginal peoples of Australia.
Hamish McGowan et al., Evidence of ENSO* mega-drought triggered collapse of prehistory Aboriginal society in northwest Australia. GEOPHYSICAL RESEARCH LETTERS, VOL. 39, 2012. Pay per viewLINK [doi:10.1029/2012GL053916]
Abstract
The Kimberley region of northwest Australia contains one of the World’s largest collections of rock art characterised by two distinct art forms; the fine featured anthropomorphic figures of the Gwion Gwion or Bradshaw paintings, and broad stroke Wandjina figures. Luminescence dating of mud wasp nests overlying Gwion Gwion paintings has confirmed an age of at least 17,000 yrs B.P. with the most recent dates for these paintings from around the mid-Holocene (5000 to 7000 yrs B.P.). Radiocarbon dating indicates that the Wandjina rock art then emerged around 3800 to 4000 yrs B.P. following a hiatus of at least 1200 yrs. Here we show that a mid-Holocene ENSO forced collapse of the Australian summer monsoon and ensuing mega-drought spanning approximately 1500 yrs was the likely catalyst of this change in rock art. The severity of the drought we believe was enhanced through positive feedbacks triggered by change in land surface condition and increased aerosol loading of the atmosphere leading to a weakening or failure of monsoon rains. This confirms that pre-historic aboriginal cultures experienced catastrophic upheaval due to rapid natural climate variability and that current abundant seasonal water supplies may fail again if significant change in ENSO occurs. 
See also article at Past Horizons (h/t Pileta). 
_________________________________________________
 
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Posted by on December 13, 2012 in Australia, climate, Epipaleolithic, rock art

 

Toba supervolcano matched with ice cores

No ashes or tephra was found in the ice sheets of Greenland or Antarctica but the supervolcano left other marks in form of very large acidity spikes (sulphates), etc:

Source: Science Daily
As you probably know, Toba caldera is located in Sumatra and its explosion was surely the largest supervolcano ever experienced by Humankind, leading to particularly cold period. 
We know since Petraglia 2007[PPV] that peoples with an African-derived techno-culture lived in South Asia before and after the dramatic episode. However it is unclear how exactly the volcano affected our ancestors beyond that.
Reference paper:
A. Svensson et al., Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 kyr BP). Climate of the Past, 2012. Open access ··> LINK [doi:10.5194/cpd-8-5389-2012]
 
 
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Posted by on November 5, 2012 in climate, Middle Paleolithic, out of Africa, supervolcano

 

Younger Dryas meteorite impact theory consolidated

The revealing micro-spherules
After sometimes heated debates, it seems that the theory of a meteorite impacting on Earth, probably above Canada, at the beginnings of the Younger Dryas and probably related to megafauna extinctions seems to be gaining more and more weight.
Malcom A. LeCompte et al. Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis. PNAS 2012. Pay per view (for 6 months/depending on world region) ··> LINK [doi]

Abstract

Firestone et al. sampled sedimentary sequences at many sites across North America, Europe, and Asia [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 106:16016–16021]. In sediments dated to the Younger Dryas onset or Boundary (YDB) approximately 12,900 calendar years ago, Firestone et al. reported discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules attributed to cosmic impacts/airbursts. The microspherules were explained as either cosmic material ablation or terrestrial ejecta from a hypothesized North American impact that initiated the abrupt Younger Dryas cooling, contributed to megafaunal extinctions, and triggered human cultural shifts and population declines. A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al. (2009) Proc Natl Acad Sci USA 104:18155–18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al., but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell et al. We found abundant YDB microspherules at all three widely separated sites consistent with the results of Firestone et al. and conclude that the analytical protocol employed by Surovell et al. deviated significantly from that of Firestone et al. Morphological and geochemical analyses of YDB spherules suggest they are not cosmic, volcanic, authigenic, or anthropogenic in origin. Instead, they appear to have formed from abrupt melting and quenching of terrestrial materials.

Most interesting in this research is that it was done directly at an archaeological layer of the Clovis clulture, what makes the chronology very solid.

Also the authors claim that some of the negative reports did not follow the protocol to detect the spherules and that is why they missed them, stirring controversy.

Partial source: Science Daily.

See also for background (this blog and its predecessor in reverse chronological order):

 

The "Little Ice Age" of the Bronze Age

It has been known now that, roughly coincident with much of the Western and Central European Bronze Age, a strong cold spell similar to the Little Ice Age, which marked much of Modern Age.
I. Schimmelpfennig et al., Holocene glacier culminations in the Western Alps and their hemispheric relevance. Geology 2012. Pay per view ··> LINK [doi:10.1130/G33169.1]
Abstract

The natural variability of Holocene climate defines the baseline to assess ongoing climate change. Greenland ice-core records indicate warming superimposed by abrupt climate oscillations in the early Holocene, followed by a general cooling trend throughout the middle and late Holocene that culminated during the Little Ice Age (LIA). Tropical precipitation changes correlate with these patterns throughout the Holocene. Here we use mountain glaciers in the European Alps to reconstruct the regional Holocene climate evolution and to test for a link between mid-latitude, North Atlantic, and tropical climate. Our precise 10Be chronology from Tsidjiore Nouve Glacier, western Swiss Alps, indicates a glacier culmination during the earliest Holocene ∼11.4 k.y. ago, likely related to the Preboreal Oscillation. Based on our data, no Holocene glacier advance of similar amplitude occurred until ∼3.8 k.y. ago, when the glacier reached LIA limits. The 10Be ages between 500 and 170 yr correspond to the LIA, while the youngest 10Be ages overlap with the historically recorded post-LIA glacier positions. Integrating our data with existing records, we propose a hemispheric climate link between the Alps, North Atlantic temperature, and tropical precipitation patterns for the Holocene, supporting the concept of a pervasive climate driver. These findings from northern mid-latitudes are consistent with the hypothesis formulated for the tropics that the Earth’s thermal equator, responding to North Atlantic temperature changes, might have migrated southward throughout the Holocene, reaching the southern turning point toward the end of the LIA.

The river Thames froze often in the 17th and 18th centuries (A. Hondius)

 
The dates mentioned, between c. 1800 and 1200 BCE are coincident with the bulk of the Bronze Age in Europe (except for the Balcans and West Asia, where is the late phase of the Bronze Age). Ironically it was a rather prosperous and interactive period that ended up in many civilizational collapses from Iberia to Anatolia soon after the temperatures went up again (beginnings of the Iron Age). 

By this I am not implying that the temperature cycle and the prehistory/proto-history cycle are related in any obvious way but can’t help notice that “our” Little Ice Age was also a period of expansion and prosperity (at least for some) and that we may now be heading to civilizational collapse as well as temperatures raise. Just a coincidence maybe…

More details at PysOrg (h/t Pileta[es]).

 
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Posted by on September 13, 2012 in Bronze Age, climate