Last week, Lorraine led a discussion about the recent article in Nature Communications that focuses on the genetic prehistory of human populations in Central America. It highlights new evidence from skeletal remains of Early-Middle Holocene individuals found within caves of the Toledo District (just south of Stann Creek). Thanks to all who participated.

Douglas J. Kennett , Mark Lipson, Keith M. Prufer, David Mora-Marín , Richard J. George,
Nadin Rohland, Mark Robinson, Willa R. Trask, Heather H. J. Edgar, Ethan C. Hill, Erin E. Ray, Paige Lynch, Emily Moes, Lexi O’Donnell, Thomas K. Harper, Emily J. Kate, Josue Ramos, John Morris, Said M. Gutierrez, Timothy M. Ryan, Brendan J. Culleton, Jaime J. Awe, and David Reich. (2022). “South-to-north migration preceded the advent of intensive farming in the Maya region.” Nature Communications, 13:1530. https://doi.org/10.1038/s41467-022-29158-y | http://www.nature.com/naturecommunications

Summary:

This article pertains to the Bladen Paleoindian and Archaic Archaeological Project (BPAAP) and the research conducted at two Belize rock-shelter sites known as Mayahak Cab Pek (MCHP) and Saki Tzul (ST). These shelters contained archaeological deposits dating back to ~12,000 cal. BP. Researchers selected 20 individuals appropriate for genomic and stable isotope sampling. Individuals dated to between 9,600 and 3,700 cal. BP, with an apparent gap in the skeletal record between 7,300 and 5,600 cal. BP. The individuals who fell within the 9,600 to 7,300 cal. BP range owed their ancestry to an early-splitting branch of humanity’s first southern dispersal into the Americas during the Late Pleistocene. Sometime between 7,300 to 5,600 cal. BP, there was a south-to-north movement into southeastern Yucatan. The individuals who fell within the 5,600 to 3,700 cal. BP range owed their ancestry to the descendants of earlier dispersals from the north-to-south and south-to-north. Linguistic and paleoecological data were marshalled to infer a subsequent northward migration of Chibchan-related populations from northern South America and southern Central America. Genetic characterizations of modern Maya peoples reflect these latter (post-5,600 cal. BP) population events.

Questions:

1. According to the authors, “Stable isotope dietary data from these individuals show increases in their consumption of maize starting after 4,700 cal. BP, but it is unclear if this dietary shift represents local adoption of more intensive maize cultivation or a new population of maize farmers moving into the region.” Based on the information provided in this article, which would you ascribe to the increases in maize horticulture and consumption: (a) adoption of maize and other domesticates by local forger-horticulturalists, (b) the intrusion of more horticulture-oriented populations with new varieties of maize, or (c) combination of (a) and (b).
2. Individuals were found in the Hoyo Negro (Black Hole) sinkhole of the Tulum area and the Naharon cave of Quintana Roo, with dates of 10,976 +/- 20 ¹⁴C y BP (12,910 – 11,750 cal. BP) and 11,670 ) +/- 60 ¹⁴C y BP (13,721 – 13,354 cal. BP), respectively. Are we able to fit these individuals into the scheme presented by Kennet et al.? What information would we need?
3. Terminology matters… doesn’t it? In the article, Kennet et al. describe their skeletal populations as representing the “first” migration into the Americas. Dating to between 9,600 and 7,300 cal. BP, is this an accurate description? Why does it matter?
4. The specific content of this article may lie outside the expertise of many members of our group, but a concept/concern that we are all familiar with is sample size. How confident are you in the broad-strokes picture of human migration painted by this paper? Which story is of greater interest to you, local/specific or global/general? Why?