Weather Report from Longgushan

Teilhard's theory of sedimentation at Longgushan has stood the test of time, and it is still accepted in large part by the modern international team of geoscientists who have worked on the site.7 Teilhard noted changes in sediments and fauna related to geological uplift of the area and to a trend toward increasingly colder climate. But there were other changes in the sediments and in the fossils that could not be explained by altitudinal changes and the impending Ice Age alone. Smaller-scale fluctuations from warm to cold occurred within the general trend toward colder conditions. The implications for understanding Homo erectus behavior in this record are profound.

In a masterful synthetic study of all paleoclimatic data from the Longgushan cave, in 2000, Chinese geologists Chunlin Zhou and his colleagues correlated the climatic fluctuations that Teilhard had first seen with the global curve of climate change in the Pleistocene Epoch.8 For the first time it was possible to correlate specific layers in the cave (and their enclosed hominid fossils and stone tools) with a detailed reconstruction of the environmental conditions in northern China at the time. For their "synthetic climatic index" Zhou and his colleagues incorporated such measures as weathering of sediments at each stratigraphic layer. For this index they counted individual grains of quartz sand in a standardized sample and compared this number to the number of grains of the mineral feldspar. Higher percentages of quartz show more washing in of sand from the ground surface than bedrock-derived feldspar, and these peaks of the index correspond to warmer and wetter climatic conditions. During periods in which there was less quartz than feldspar, high proportions of cold-adapted plants, such as the grasses Artemesia and Selaginella, were seen.

Paleomagnetic History Earth

The global paleomagnetic stratigraphy for the past 2.5 million years. The paleomagnetic signature of sediments at Longgushan have assisted in dating the deposits. "Normal" refers to those times in earth history when magnetic polarity was north-facing, as today. "Reversed" refers to periods when magnetic polarity was south-facing. The boundary between the Brunhes Normal and the Matuyama Reversed Chrons occurs in Layer 14 of Locality 1, indicating that these sediments underlying the hominid-bearing deposits of the site are over 780,000 years old. my = millions of years.

The global paleomagnetic stratigraphy for the past 2.5 million years. The paleomagnetic signature of sediments at Longgushan have assisted in dating the deposits. "Normal" refers to those times in earth history when magnetic polarity was north-facing, as today. "Reversed" refers to periods when magnetic polarity was south-facing. The boundary between the Brunhes Normal and the Matuyama Reversed Chrons occurs in Layer 14 of Locality 1, indicating that these sediments underlying the hominid-bearing deposits of the site are over 780,000 years old. my = millions of years.

Isotopes also play a part in reconstructions of past climate. In 1985 Xie and his colleagues analyzed the relative amounts of the elements barium and strontium in sediments from Locality 1.9 When there is a high ratio of barium to strontium, the climate can be inferred to have been wetter and warmer because, as sediments weather, strontium is leached out and lost from the soil. These data were also used by Zhou and his colleagues to put together their climatic index. The peaks of graphed strontium/barium ratios through time fit nicely with the other measures of climate from

Synthetic Climatic Deep Sea Oxygen Loess Clay/Silt

Index Isotope Record

Synthetic Climatic Deep Sea Oxygen Loess Clay/Silt

Index Isotope Record

The Pleistocene Epoch, known colloquially as the "Ice Age," was actually a time of fluctuating conditions—from very cold to very warm. These diagrams, constructed by paleo-climate researchers Chunlin Zhou and his colleagues (2000), record the climate in northern China during the time that Homo erectus lived near Dragon Bone Hill. A Synthetic Climatic Index integrates data from weathering of sediments. The Deep-Sea Core records temperature changes as a function of oxygen isotopes. "Loess" accumulates during periods of cold, glacial conditions. As a composite, these data show that Homo erectus adapted to changing conditions, living near Dragon Bone Hill in warm interglacial conditions and probably migrating to the south during glacial conditions.

Longgushan, such as the record of loess. We will return to the climatic story that isotopes tell when we correlate Chinese Homo erectus with global patterns of change and migration in chapter 8.

During the relatively "good times,"—the interglacial periods, when rainfall was plentiful, temperatures habitable, and game and plant foods abundant—Homo erectus lived around, and even in, the Dragon Bone Hill cave. We know this by the records of stone tools and cut marks left on bones in the cave. During cold, "glacial" periods, the wind swept off the Mongolian steppes carrying the dry, ice-ground loess, and the large mammals went south. Only arctic-like small mammals and cold-adapted plants are recorded in the Longgushan sediments during these periods. Hominid fossils are rare or nonexistent during the cold phases. Where did they go?

The implications of the paleoclimatic record at Longgushan are that Homo erectus was still largely a tropical species, migrating south to be with the warm-adapted southern China fauna and flora (species like the panda and the bamboo tree), when it became cold, and returning to northern China during the warm periods. The Qinling Mountains cordon off northern China from southern China in an east—west wall that created a major physical and climatic barrier even then. These mountains would have essentially shielded southern China from the glacial winds blowing from the north during cold periods of the Pleistocene. Southern China would have served Homo erectus populations as a refuge when northern China was too cold to be habitable.

The large-scale migratory pattern that we deduce for Homo erectus emphasizes the adaptive limitations of this species compared to modern humans. Homo sapiens groups such as the Inuit, Saami, Paleo-Indians, and ancient Siberians all adapted to frigid climates in the far north, building effective shelters, successively finding food by hunting, herding, and gathering, and keeping warm with well-made clothing and fire. It has also recently been suggested that dogs were domesticated to help Homo sapiens hunt and fend off predatory hyenas.10 We must conclude that the essential components of these types of adaptations were missing in Homo erectus.

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Responses

  • DENNIS HANSELMAN
    What weather condition did homo erectus?
    8 years ago

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