[adastra22]

That's not what I mean by "in context." For radiocarbon dating, the term "in context" means that it is established that the radioisotopes were captured at a time coinciding with or in some way limiting upon the date of the activity under consideration, in this case the construction of the pyramid structure.

1. Soil is alive--it is constantly interacting with the atmosphere, if it is close enough to the surface, and the nutrients which seep through it and the various organic matter that lives inside it. You might be able to reliably date a peet bog or other undisturbed anoxic system, but packed soil in a tropical environment is a bit more suspect (no matter how buried). Otherwise the "date" of the soil is continuously evolving based on local conditions that are difficult to calibrate. That's why archeologists typically date things like the charred remains of a cooking fire, not soil.

2. Ok, assume that these dates are in any way meaningful. That still doesn't establish the age of the structure as claimed in the article. Surface dates are totally suspect for the reasons I gave above, but for the purpose of this point we can grant it. So Unit 1 provides only an unsurprising minimum age. The packed dirt in Unit 2 & 3 on the other hand is construction back-fill: the radiocarbon age of the packed soil is the average age of the soil they used in construction. But that soil was already old. Think about it this way: if you took that surface soil from Unit 1 and put it on top of your house porch, we'd now be able say your porch was constructed between 2,000-1000BC.

This article establishes that there were two construction phases, and that these phases were likely carried out at different times because different sources of back-fill soil were used. But that's it. The actual dates have no relation to the human activity.