In northern Peru, archaeologists have discovered the oldest adobe monumental building in the New World. The mud brick walls hidden inside the hill known as Los Morteros are already 5100 years old and thus the oldest evidence of a systematic use of such bricks for architectural buildings. Remains of votive offerings also suggest that the pre-Columbian monument once served ritual purposes.
Mud bricks are an important building material in many regions of the world: Around 30 percent of the world’s population and half of all people in developing countries still live in mud buildings today. The adobe bricks, also known as adobe bricks after their Spanish name, were of particular importance in pre-Columbian America. There they shaped the architectural tradition for thousands of years and were used for the construction of enormous monuments.
A hill turns out to be a monumental building
But despite this enormous importance for the architecture of the new world, the origin of this building material has so far been in the dark: “None of the available studies has taken a closer look at the roots of adobe production or the technological development of its structure and composition,” explains Ana Cecilia Mauricio from of the Pontifical Catholic University of Peru and their colleagues. The research team took a chance to find out more about new discoveries in Los Morteros in northern Peru.
The 150 meter wide, 200 meter long and 15 meter high Los Morteros hill is located in the middle of a barren desert landscape, apparently in the middle of nowhere – for this reason, among other things, it was considered of natural origin for a long time. It was not until 2010 that ground radar analyzes revealed that remains of architectural structures were hidden beneath the layers of the earth. As a result, Mauricio and her team began to explore these remains in excavations in 2012. “We were able to prove that the Los Morteros Hill is not a natural structure, but a hill structure that was built in two complex periods of settlement,” report the archaeologists.
Mud bricks in their most original form
The excavations brought to light, among other things, the remains of around 5100 year old buildings. Its walls were made of mud bricks that had been piled on a foundation of rock and mortar. Inside the rooms, a thick layer of clay formed the floor and the walls were covered with clay plaster. In one of these rooms, the researchers discovered three children’s graves, which were apparently part of a larger votive offering. “This ritual activity, as well as the large size and construction, suggests that this adobe building once had monumental dimensions and fulfilled an equally important function,” state Mauricio and her colleagues.
The really exciting thing about this building, however, were the walls and their mud bricks: “All bricks were roughly rectangular and about 30 to 40 centimeters long, ten centimeters wide and seven centimeters high,” reports the team. According to them, the structure of these bricks suggests that they were cut directly from a natural, water-saturated layer of clay and then dried as they were. In this and in their old age, these adobe bricks differ from all those previously known from South and Central America: “In their unique composition, their internal structure and their age, the adobe bricks from Los Morteros show the beginnings of this architectural tradition,” write Mauricio and her team . At the same time, the Los Morteros mound is the oldest known monumental building in the New World that was built from adobe bricks.
As the team explains, the still simple, unmodified adobe bricks in this building mark a phase in which the people of this region were apparently still experimenting with this nature-based building material. “It was only in the following time periods that the cultures of this region developed the recipes for the production and drying of the more durable, mass-produced mud bricks that were to shape the great architectural traditions of pre-Columbian Peru,” the archaeologists state.
Source: Proceedings of the National Academy of Sciences, doi: 10.1073 / pnas.2102941118