Humans were long thought to have begun occupying the Peruvian settlement of Machu Picchu between 1440 and 1450 CE. However, a team led by anthropologist Dr. Richard Burger used accelerator mass spectrometry to uncover evidence that it was occupied ________ 1420 CE, according to Burger, humans were likely inhabiting the area.

Which choice completes the text so that it conforms to the conventions of Standard English?