April 10, 2022
Jaime Awe has done a study on two rock shelters in the rainforest of Belize. 85 skeletons have been unearthed at those rock shelters, 50 of these individuals have been radio carbon dated to 1,000-9,600 years ago. Geneticists then studied these remains and obtained high quality DNA from the inner ear bones of 20 of these individuals. They found that the oldest individuals in this group lived 9,600 to 7.300 years ago. This is the oldest DNA from any rain forest rock shelter. These resemble hunter-gatherers coming in an ancient migration from the north. But at 5,600 years ago, the DNA shifted and showed these individuals came from individuals living from Columbia to Costa Rica who are Chibcha speakers.
The Maya got half of their DNA from the southern immigrants, the remainder from the most ancient settlers who emigrated from the north and some from the Mexican highlands. Other researchers studied the teeth of the rock shelter people. The teeth showed a steady increase in maize consumption over time. Between 5,600 to 4,000 years ago, maize consumption soared to 50% of the diet. Maize was partially domesticated 9.000 years ago in southwest Mexico, but not fully domesticated till 6,500 years ago in Peru and Bolivia. These southern migrants brought their fully domesticated maize to Belize 5.600 years ago.
Thus it was migrants from South America who were responsible for kicking off the Maya civilization.
Science.org has the report here.