Louisiana State University (LSU) has two mounds built by Native Americans on its campus. The mounds are heritage listed, regarded as being around 5-6,000 years old – older than Egypt's great pyramids. New work indicates they're almost twice that age – probably making them the oldest known human-made structures in the Americas, and possibly the oldest on Earth.
The LSU Campus Mounds are famous enough to have their own Wikipedia page, and the university considers them important enough to have taken steps to protect them from partying students, who once slid down them to celebrate sporting victories and sometimes even drove vehicles onto them. Nevertheless, they haven't been widely regarded as being of national, let alone world significance.
Professor Brooks Ellwood helped excavate the mounds in 2012 and 2018 and has an office strolling distance from them. Great for ease of access, not so good for applying for travel grants. He now believes there was an error in the dating, and the true age is 11,300 years.
Ellwood has a distinguished career, but most of it relates to far more distant eras. Most of his hundreds of published papers relate to deep geologic time, such as the Permian-Triassic boundary 252 million years ago.
Past studies of the mounds revealed bone fragments and a layer of ash. The ash was apparently regarded as having little use for telling archaeologists about the age and purpose of the mounds and wasn't investigated further. However, on waking from a nightmare, Ellwood remembered ashy material he had found at an excavation in Albania 30 years ago. When he compared slides taken at the two sites he noticed something different, leading him to look deeper.
Besides estimating the mounds are much older than previously thought, Ellwood's research on them has led him to some new ideas about their purpose. Although commonly referred to as burial mounds, anthropologists have doubted they contained bodies.
Closer examination of the Louisiana ash revealed tiny bone fragments identified as being of mammalian (and therefore possibly human) origin. The fragments were encased in material from reed and cane that had apparently been burnt with them. Neither material was used for cooking by Native Americans because they burn at too high a temperature. It was the contrast between this, and the ash provided by the cooler Albanian cooking fires that had troubled Ellwood's subconsious.
“The only logical thing that it could have been is for human beings,” Ellwood told The Baton Rouge Advocate.
Ellwood's paper on the mounds has been submitted, but is yet to pass peer review, and his colleagues are cautious about commenting until it has. Approval from native leaders may be needed for some tests that could prove or disprove his theories.
If Ellwood's right, however, the mounds must have been built to last. Considering the makers lacked metal tools and probably agriculture, the knowledge of engineering is remarkable. Like many similar mounds, those on the university campus look out over the Mississippi and are likely to have hosted ceremonies and gatherings.