Indians who inhabited the territory of today’s U.S. state of Louisiana more than 3,000 years ago were highly skilled engineers who were able to build massive earthworks. This is the opinion of archaeologists from Washington University in St. Louis.

The scientists, whose findings are published in the journal Southeastern Archaeology, have found that Native North Americans were not primitive hunter-gatherers and composed after themselves structures that are difficult to build even with modern technology.

“We as a research community-and the general population-underestimated Native people and their ability to do this work and do it quickly the way they did,” said lead author Tristram R.

The researchers also specified that one of the most remarkable features of the earth fortifications built by the ancient Indians is that they were able to stand for more than 3,000 years without any failure or serious erosion.

“They really were incredible engineers with very sophisticated technical knowledge,” stressed the scientist.

That said, theoverty Point World Heritage Site in northern Louisiana that the scientists investigated, which consists of a massive dirt hill over 20 meters high and concentric semicircular hills, was built about 3,400 years ago from nearly 1.5 million cubic meters of soil without the use of modern tools, pets or even wheeled carts.

Scientists believe the site had religious significance. Using modern research methods, including radiocarbon dating, microscopic soil analysis and magnetic soil measurements, they found that the earthwork was done quickly.

“Depending on the speed of excavation and construction, as well as the amount of earth moved, this data shows that local people came to the site and worked in a coordinated manner. This in itself is remarkable because hunter-gatherers were not capable of engaging in these activities,” Kidder noted.

In doing so, scientists also learned that Native Americans mixed different types of soil – clay, silt and sand – according to a calculated recipe to make the structures stronger, which has resulted in them surviving to this day.

“Like Roman concrete or tamped earth in China, Native Americans discovered sophisticated ways to mix different types of materials to make them virtually indestructible, even though they are not compacted. There’s some magic there that our modern engineers haven’t been able to figure out yet,” explained the study’s lead author.