such as "Introduction", "Conclusion"..etc
Mar. 29, 2009 — Unraveling the origins of
agriculture in different regions around the globe has been a challenge
for archeologists. Now researchers writing in the Proceedings of the National Academy of Sciences
report finding evidence of early human experiments with grain
cultivation in East Asia. They gathered this information from an
unlikely source―dog and pig bones.
The dog and pig bones, as well as bones of other animals analyzed in
the study, come from an archaeological site in a region of northwest
China considered to be a possible early center of East Asian
agriculture. Chemical traces within the dog bones suggest a diet high
in millet, a grain that wild dogs are unlikely to eat in large
quantities, but that was a staple of early agricultural societies in
northwest China. "If the dogs were consuming that much millet, their
human masters were likely doing the same," says Seth Newsome, a
coauthor on the study and a post-doctoral associate at the Carnegie
Institution's Geophysical Laboratory, where the chemical analysis was
The bones come from a Neolithic site known as Dadiwan, in China's
western Loess Plateau, excavated first by a Chinese team in the late
70s and early 80s, and in 2006 by a team from the University of
California, Davis, and Lanzhou University in China. Humans occupied the
site during two main phases, from 7,900 to 7,200 years ago (Phase 1)
and from 6,500 to 4,900 years (Phase 2). Though some fossil remains of
millet plants have been found in both of these deposits, the fossils
don't directly reveal how much millet contributed to the local diet.
To address this question, the researchers turned to a technique
known as stable isotope analysis. Atoms of elements such as carbon come
in different forms (isotopes) which are chemically similar, but can be
distinguished in the laboratory by minute differences in their mass.
Certain kinds of plants known as C4 plants tend to concentrate heavier
carbon isotopes as they grow, compared to other plants known as C3
plants. Animals with diets high in C4 plants also tend to concentrate
heavier isotopes in their bones. As it turns out, millet is one of the
few C4 plants that grow in arid northwest China, making the carbon
isotopes in bone a good indicator of a millet-rich diet.
The researchers found that the most of the dog bones from the Phase
1 deposits bore the isotopic signature of a high millet diet. This
suggests that these dogs were domesticated and fed by humans who
harvested millet. Bones of pigs from the site tell a slightly different
story. In the Phase 1 deposits, the pig bones don't show signs of
millet in the diet, so they were probably wild pigs hunted and eaten by
people. But pig bones from Phase 2 do have the isotopic signature of
millet, so they were probably domesticated by this time.
"Our results help fill in the picture of how agriculture arose in
this part of the world," says Newsome. "There has been speculation that
agriculture spread north from southern rice-farming areas, but the
Phase 1 people were likely experimenting with agriculture by
cultivating local grains. This simple system was later replaced by
people in Phase 2 who had a much more developed agricultural system"
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