A-maize-ing Grains... Two early agriculture discoveries
Submitted by coldrum on Thursday, 02 April 2009 Page Views: 1320
DiscoveriesEarly Agriculture Left Traces in Animal Bones.Researchers writing in the Proceedings of the National Academy of Sciences report early human experiments with grain cultivation in East Asia. They gathered this information from an unlikely source―dog and pig bones.
Earliest Evidence of Domesticated Maize.
Maize was domesticated from its wild ancestor more than 8700 years according to biological evidence uncovered by researchers in the Mexico’s Central Balsas River Valley. This is the earliest dated evidence -- by 1200 years -- for the presence and use of domesticated maize.
Early agriculture left traces in animal bones (continued-)
The dog and pig bones come from a 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 (Carnegie Institution's Geophysical Laboratory).
The bones come from a Neolithic site known as Dadiwan, in China's western Loess Plateau, excavated first in the late 70s and early 80s, and again in 2006. 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 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.
For more, see Eureka Alert.
Earliest Evidence of Domesticated Maize (continued-)
Anthony Ranere (Temple University) and Dolores Piperno (Smithsonian National Museum of Natural History), reported findings in two studies.
According to Ranere, recent studies have confirmed that maize derived from teosinte, a large wild grass that has five species growing in Mexico, Guatemala and Nicaragua. The teosinte species that is closest to maize is Balsas teosinte, which is native to Mexico’s Central Balsas River Valley.
“We went to the area where the closest relative to maize grows,” said Ranere. “That wasn’t surprising since molecular biologists had determined that Balsas teosinte was the ancestral species to maize. So it made sense that this was where we would find the earliest domestication of maize.”
The study began with Piperno finding evidence in the form of pollen and charcoal in lake sediments that forests were being cut down and burned in the Central Balsas River Valley to create agricultural plots by 7000 years ago. She also found maize and squash phytoliths -- rigid microscopic bodies found in many plants -- in lakeside sediments.
Ranere, an archaeologist, joined in the study to find rock shelters or caves where people lived in that region thousands of years ago. His team carried out excavations in four of the 15 caves and rock shelters visited in the region, -only one of them yielded evidence for the early domestication of maize and squash.
Ranere excavated the site and recovered numerous grinding tools. Radiocarbon dating showed that the tools dated back at least 8700 years. Ranere said that maize starch, which is different from teosinte starch, was found in crevices of many of the tools that were unearthed.
“We found maize starch in almost every tool that we analyzed, all the way down to the bottom of our site excavations,” Ranere said. “We also found phytoliths that comes from maize or corn cobs, and since teosinte doesn’t have cobs, we knew we had something that had changed from its wild form.”
For more, see newswise.com.
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