Humans dwelt in Ice-Age Tibet
Footprints and a fire found from 20,000 years ago.
Handprints and footprints 20,000 years old reveal that people lived on the Tibetan plateau at the height of the Ice Age – 16,000 years earlier than scientists had thought. The newly found signs of life cast doubt on the idea that a glacier a kilometre thick covered the plateau at that time.
David Zhang and S. H. Li of the University of Hong Kong found the marks of at least six individuals, including two children, in marble-like rocks that were once soft mud on a mountain slope 85 kilometres from the Tibetan capital, Lhasa1.
They also found a fireplace nearby, with the remains of a primitive stove, suggesting that the site was a camp, perhaps even a settlement.
Until now, the oldest known settlements on the Tibetan plateau dated from late Neolithic times, around 4,000 years ago. This had led some researchers to conclude that humans first migrated into Tibet around this time.
The encampment is also a nail in the coffin for the ice-covered plateau hypothesis. It indicates that at least part of the plateau, which today is 4,000 metres high on average, was free of ice even during this frigid period of Earth’s history.
The very hot spring that probably attracted the Ice-Age settlers also preserved their marks for posterity. The spring water is rich in dissolved minerals and gases. As carbon dioxide gas bubbles out of the water, minerals such as calcite precipitate out. This forms a soft mineral mud. As the mud dries, it turns into a hard, durable limestone called travertine.
So, thanks to the hot spring, the mountainside made plaster casts of the Ice-Age people who lived on it. Nineteen hand- and footprints are clearly visible in the stone surface.
Zhang and Li date the travertine deposit by the tiny grains of quartz that got trapped within it while the mud solidified. Quartz acts as a mineral clock. When heated, it emits light in proportion to the time that has elapsed since it was last warmed or exposed to sunlight.
This technique is called thermoluminescence dating. Energy builds up in trapped quartz because it is exposed to radiation from natural radioactive elements such as uranium and thorium in surrounding minerals. It emits this energy as light: the longer the exposure time, the higher the energy and so the brighter the light.
Because heat or sunlight releases the trapped energy, the quartz grain clock would have been set to zero when the grains became embedded in the warm mud from the spring.
- Zhang, D.D. & Li, S. H.Optical dating of Tibetan human hand- and footprints: an implication for the palaeoenvironment of the last glaciation of the Tibetan Plateau. Geophysical Research Letters, 29, Published online DOI: 10.1029/2001GL013749 (2002).
Alle Nachrichten aus der Kategorie: Interdisciplinary Research
News and developments from the field of interdisciplinary research.
Among other topics, you can find stimulating reports and articles related to microsystems, emotions research, futures research and stratospheric research.
A rich source of nutrients under the Earth’s ice sheets
Data from Greenland and Antarctica show: under ice trace elements are mobilised at higher rates than previously assumed. Trace elements such as iron, manganese and zinc are an integral part…
Life cycle of moon jellyfish depends on the microbiome
Research team at Kiel University uses Aurelia aurita as an example to demonstrate the relationship between microbial colonization and reproduction in marine cnidarians The body tissue of all multicellular living…
Fraunhofer IWM closes gaps in the mechanics of materials digital value chain
The greatest potential of digitalization in companies in which materials play a prominent role lies in the cross-process linking of materials data. This promises to shorten component development times, faster…