Archaeologists discover Mayan 'melting pot'.

• Position: Civilization

Researchers working in Guatemala have unearthed information about the Mayan civilization's transition from a mobile, hunter-gatherer lifestyle to a sedentary way of life. Led by archaeologists Takeshi Inomata and Daniela Triadan, the team's excavations of the ancient Mayan lowlands site of Ceibal suggest that, as the society transitioned from a heavy reliance on foraging to farming, mobile communities and settled groups coexisted and may have come together to collaborate on construction projects and participate in public ceremonies.

The findings, published in Proceedings of the National Academy of Sciences, challenge two common assumptions: that mobile and sedentary groups maintained separate communities, and that public buildings were constructed only after a society fully had put down roots.

"There has been the theory that sedentary and mobile groups coexisted in various parts of the world, but most people thought the sedentary and mobile communities were separate, even though they were in relatively close areas," explains Inomata, lead author. "Our study presents the first relatively concrete evidence that mobile and sedentary people came together to build a ceremonial center."

A public plaza uncovered at Ceibal dates to about 950 B.C., with surrounding ceremonial buildings growing to monumental sizes by about 800 B.C. Yet, evidence of permanent residential dwellings in the area during that time is scarce. Most people still were living a traditional hunter-gatherer-like lifestyle, moving from place to place throughout the rain forest, as they would continue to do for five or six more centuries.

The area's few permanent residents could not have built the plaza alone...