LOS ANGELES — U.S. and Mexican archaeologists have discovered one of the oldest tombs in Mesoamerica, a burial chamber from at least 2,500 years ago in the state of Chiapas that contains the remains of what appears to be one of the first powerful rulers of the Zoque people.

“There certainly isn’t any tomb that is earlier … and this is the only one found at the very crest of a pyramid, which makes the find rather special,” said archaeologist Bruce R. Bachand of Brigham Young University, one of the tomb’s discoverers.

The tomb “is by far the most elaborate” of those from the period, he added, and is the only one that has been found to contain human remains. Because of the acidic soil in the region and the high humidity, remains tend to decompose relatively rapidly.

The find, announced May 17, sheds new light on the origins of the Zoque, who are generally thought to be descended from early emigrants from the Olmec culture to the west.

“For so long, the Olmec people have been considered the ‘Mother Culture’ where everything started in Mesoamerica,” said archaeologist Carl Wendt of California State University, Fullerton, not involved in the research. “This find is showing that complexity is not necessarily confined to the Olmec area.”

The tomb was near the top of a three-story pyramid at the site of Chiapa de Corzo, about 60 miles southeast of the Olmec coastal city of La Venta on the Gulf of Mexico. Archaeologists  have been working at the site for two years, attempting to learn more about the little-known people referred to as the Zoque, a linguistic appellation more than an ethnic one.

Evidence suggests the site was settled about 1200 B.C. by Mixe-Zoquean speakers who had strong ancestral ties to the Olmec. The village was probably initially a way station on an Olmec trading route, but evidence from the tomb and the rest of the site suggests that it had become largely independent by the time of the tomb’s construction, between 700 and 500 B.C.

The Zoque flourished for more than 2,000 years, but in A.D. 1494 they were invaded and defeated by the Aztecs.