Today's post is by guest blogger: Jana Haasz
Taken at the excavation of an elite Moche female tomb
If you haven’t seen the exhibit “Science on a Half-Shell,” I highly recommend that you hurry up! Besides these bivalves giving us clues about evolution through the study of theirs, it turns out that we can learn a lot of other interesting things about civilizations in general by studying them. Maybe not all civilizations and cultures, but clam shells are aiding scientists to perhaps solve a mystery about a civilization that vanished in Peru somewhere around 800 C.E.
The civilization was the Moche (Mo-shay), and archaeologists and scientists have been able to surmise the kind of culture they developed because of mummified remains, and of course architectural, and archaeological evidence; however, as much as we learned from the speculations about the way these people lived, that’s how little we know about why they disappeared.
Ruins of their cities are tourist destinations in Peru. Their civilization lived in and around the modern day cities of Moche and Trujillo, and it is believed that they were not a single unified society. In other words, they did believe in the same religion, but did not have a centralized governmental system. They seemed to have been dispersed throughout the region in "clans" or groups. It is believed that they are divided into several kingdoms throughout the area, and so the total disappearance and collapse of their civilization did not occur uniformly and all at the same time.
The Moche have become famous for the exquisite pottery they created. They built strange and eerie giant pyramids, and even constructed efficient irrigation systems, and some of the aqueducts are still used today. It was a sophisticated and agriculturally based culture.
Over time, speculations about the reasons for their disappearance gradually turned to ideas that perhaps some kind of drastic climate change occurred, forcing the Moche peoples to change habits, and perhaps lose their source of food supply in their agriculturally based system. That is difficult to prove, nonetheless, especially since no writing system has been found to show us an account. In the 1970s, scientists, anthropologists, and archaeologists definitively turned their attention to seeking evidence to prove the climate change theory.
The Moche practiced gruesome and gory sacrificial ceremonies as part of religious rites, and many bodies of the Moche have been found buried with – you guessed it – clam shells.
Suddenly, it occurred to scientists to look to the clam shells for evidence that there was indeed a change in El Nino, (the band of anomalous warm wind that develops off the coast of South America and causes climate changes over the Pacific Ocean). They turned their attention to examining the changes in the shells that were buried with the bodies, which were, of course, buried at different periods throughout Moche history. Not only that, there’s actually a science called schlerochronology – the science of determining climate changes through the study of shells.
How does this work? Clams suck up carbon from the ocean during their growth stages, and the amount of carbon increases with an “upwelling.” This phenomena occurs during an El Nino, and is cooler ocean water rising to the surface. This water is generally more nutrient rich, and the extra carbon is then absorbed into the shells. This shows up bands upon the shells, much like the rings of a tree that show us the tree’s age. The bands can be dated by using radiocarbon measurements.
When this was performed on the many shells found at Moche burial sites, the findings supported the El Nino climate change theory.
During an El Nino event, droughts can occur in some areas and flooding in others, which of course, requires adaptation in an agricultural society. Since this appears to have been a relatively long El Nino event, the changes would have been gradual, but obviously had a devastating impact on this sophisticated culture.
Who knew that a bivalve could reveal so much?
Background information: Shurkin, Jack for Livescience.com
Image credit: class.csueastbay.edu
Saturday, May 18, 2013 at 11:31AM 
