An ancient workshop on the Nottoway River
On a sandy terrace overlooking the Nottoway River in Sussex County, Virginia, lies one of the most important archaeological sites in the Americas. Cactus Hill, named for the prickly pear cactus that grows in the sandy soil, contains evidence that changed our understanding of when humans first arrived on the continent. The site, designated 44SX202, is not a cave or a permanent settlement but a stratified campsite where people have stopped for millennia. Its remarkable record is preserved within wind-deposited (eolian) sand dunes that have kept distinct layers of occupation separate for thousands of years.
Systematic excavations, led by archaeologists Joseph M. McAvoy and Lynn D. McAvoy starting in 1993, revealed a clear sequence of cultural layers. An upper layer contained classic fluted projectile points and tools associated with the Clovis culture, radiocarbon dated to about 10,920 years ago. Below this, separated by a layer of sterile sand, archaeologists found an even older cultural deposit. This pre-Clovis layer contained a different toolkit, including thin, unfluted lanceolate bifaces, polyhedral blade cores, and scrapers made from local quartzite. The presence of these tools deep below the Clovis horizon showed that people were in Virginia long before the Clovis hunters appeared.
Dating the deep past
The claims made about Cactus Hill rest on rigorous dating techniques applied to materials from the pre-Clovis layer. Archaeologists uncovered hearth-like features containing charcoal from white pine and conifer. Using accelerator mass spectrometry (AMS) radiocarbon dating, samples from this layer produced dates ranging between 15,000 and 20,000 years ago. One important sample of white pine charcoal from a hearth was dated to 15,070 ± 70 radiocarbon years Before Present. Another sample from wood charcoal yielded a date of 16,670 ± 730 years BP.
To corroborate these findings, researchers used a different technique called Optically Stimulated Luminescence (OSL). OSL dating measures the last time the sand grains themselves were exposed to sunlight. This method determined that the sediments containing the pre-Clovis artifacts were buried between 18,200 and 18,600 years ago. The agreement between the radiocarbon and OSL dates gives scientists high confidence in the site's antiquity. Before the discoveries at Cactus Hill and a handful of other sites, the consensus was that the Clovis people were the first to inhabit the Americas around 13,000 years ago. The data from this sandy Virginia dune overturned the long-held "Clovis-First" model.