One of the earliest transitions to a politically stratified society in the Americans took place not among crop growers, but among villagers who hunted, fished and gathered wild plants along Mexico's southwestern coast about 3,500 years, ago, according to a report in the February CURRENT ANTHROPOLOGY.
This finding, along with the excavation of a coastal Peruvian settlement from the same period (SN: 1/19/91, p.38), indicates that many New World coastal societies developed without relying on agricultural techniques, which anthropologists often consider essential to the growth of civilizations.
Researchers led by anthropologist Michael Blake of the University of British Columbia in Vancouver collected 1- to 2-gram bone samples from 36 human skeletons excavated from 15 archaeological sites along the west coast of southern Mexico and Guatemala. The earliest sites date to between 2700 B.C. and 1800 B.C.; the most recent date to between A.D. 1200 and A.D. 1524.
The scientists ground up each bone sample and produced a dried gelatin for chemical analysis in a mass spectrometer. Ratios of specific carbon and nitrogen isotopes in bone signify the regular consumption of particular classes of agricultural and wild plants, as well as fish and other sea creatures.
Blake's group focused on 16 bone samples taken from "early formative" villagers, who lived in sites in southwestern Mexico from around 1550 B.C. …