James Stewart

The answer lay in Ecuador.

In early 2024, a science study using the same LiDAR techniques revealed a dense settlement network in the Upano Valley of Ecuador along the eastern foothills of the Andes Mountains.

The work, led by archaeologist Stephen Rostain and his colleagues, integrated decades of field research with LiDAR mapping, and with this combined knowledge, they uncovered the unthinkable.

Within a 300 square kilometer survey area, they found more than 6,000 anthropogenic rectangular earthen platforms and plaza structures,

connected by footpaths and roads, some 13 meters wide, and surrounded by expansive agricultural landscapes and even drainage features.

In other words, what they were looking at was not just a single lost city.

This was a patterned regional network.

They were looking at a hidden metropolis.

The sheer scale of this discovery meant it was likely home to at least 10,000, possibly 30,000 inhabitants in around 500 BCE, with the settlement lasting roughly 1,000 years.

And if you're wondering, by the way, how on earth we know that this was happening that far back, well, science has another trick up its sleeve to answer that question too.

Enter Oxford's radiocarbon accelerator unit.

This team applied radiocarbon dating to organic materials to find out just how old this civilization was.

To quickly explain how this works, every living thing absorbs carbon from the atmosphere, whether that's through photosynthesis or eating stuff that photosynthesizes.

Now, most of that is your regular carbon-12, which has six protons and six neutrons, but a tiny percentage, about one in a trillion particles of carbon, is carbon-14.

which still has six protons but has eight neutrons, so is slightly heavier.

Now, living things aren't very picky about this and will take in either type of carbon, really, but crucially, carbon-14 is radioactive and so breaks down naturally over time.

And what this means is the moment a plant or animal dies, the clock starts, effectively.

It stops taking in carbon-14, and as it decays, the amount of carbon-14 in the organism decreases.

Its half-life, therefore, that's the time taken for half of the carbon-14 in a sample to decay, is around 5,700 years.

As such, scientists can measure what percentage of the carbon in a sample is still carbon-14, and from that, can calculate how many years have passed since that organism died, which is pretty clever.