Amber M. VanDerwarker’s research while affiliated with University of California, Santa Barbara and other places

Molecular research suggests that avocados (Persea americana Mill.) were domesticated multiple times in the Americas. Seed exchange, hybridization, and cloning have played an essential role across their wild distribution from Mexico to South America to create the modern varieties of today. Archaeological sites with well-preserved and directly radiocarbon-dated botanical assemblages are rare, however, so we know very little about the complexities of the domestication process. Here, we define an early locus of avocado domestication using well-dated desiccated and carbonized avocado remains from El Gigante rockshelter in western Honduras spanning the last 11,000 y. Measurements of avocado seeds and rinds show evidence for long-term management resulting in selection for larger, more robust fruits through time that culminated by 2,250 to 2,080 calendar B.P. (cal. B.P.). However, human-directed selection for larger fruits with thicker rinds is evident as early as 7,565 to 7,265 cal. B.P. Seed morphology is similar to P. americana var. guatemalensis and is congruent with genetic data for the development of this variety in both the highlands of Guatemala and Honduras. Increases in seed size and rind thickness through time are consistent with genetic evidence for the enrichment of putative candidate genes for fruit development and ripening in this variety.

The squash family (Cucurbitaceae) contains some of the most important crops cultivated worldwide and has played an important ecological, economic, and cultural role for millennia. In the American tropics, squashes were among the first cultivated crop species, but little is known about how their domestication unfolded. Here, we employ direct radiocarbon dating and morphological analyses of desiccated cucurbit seeds, rinds, and stems from El Gigante Rockshelter in Honduras to reconstruct human practices of selection and cultivation of Lagenaria siceraria, Cucurbita pepo, and Cucurbita moschata. Direct radiocarbon dating indicates that humans started using Lagenaria and wild Cucurbita starting ~ 10,950 calendar years before present (cal B.P.), primarily as watertight vessels and possibly as cooking and drinking containers. A rind directly dated to 11,150–10,765 cal B.P. represents the oldest known bottle gourd in the Americas. Domesticated C. moschata subsequently appeared ~ 4035 cal B.P., followed by domesticated C. pepo ~ 2190 cal B.P. associated with increasing evidence for their use as food crops. Multivariate statistical analysis of seed size and shape show that the archaeological C. pepo assemblage exhibits significant variability, representing at least three varieties: one similar to present-day zucchini, another like present-day vegetable marrow, and a native cultivar without modern analogs. Our archaeobotanical data supports the hypothesis that Indigenous cucurbit use started in the Early Holocene, and that agricultural complexity during the Late Holocene involved selective breeding that encouraged crop diversification.

El Gigante rockshelter in western Honduras provides a deeply stratified archaeological record of human–environment interaction spanning the entirety of the Holocene. Botanical materials are remarkably well preserved and include important tree (e.g., ciruela (Spondias), avocado (Persea americana)) and field (maize (Zea mays), beans (Phaseolus), and squash (Cucurbita)) crops. Here we provide a major update to the chronology of tree and field crop use evident in the sequence. We report 375 radiocarbon dates, a majority of which are for short-lived botanical macrofossils (e.g., maize cobs, avocado seeds, or rinds). Radiocarbon dates were used in combination with stratigraphic details to establish a Bayesian chronology for ~9,800 identified botanical samples spanning the last 11,000 years. We estimate that at least 16 discrete intervals of use occurred during this time, separated by gaps of ~100–2,000 years. The longest hiatus in rockshelter occupation was between ~6,400 and 4,400 years ago and the deposition of botanical remains peaked at ~2,000 calendar years before present (cal BP). Tree fruits and squash appeared early in the occupational sequence (~11,000 cal BP) with most other field crops appearing later in time (e.g., maize at ~4,400 cal BP; beans at ~2,200 cal BP). The early focus on tree fruits and squash is consistent with early coevolutionary partnering with humans as seed dispersers in the wake of megafaunal extinction in Mesoamerica. Tree crops predominated through much of the Holocene, and there was an overall shift to field crops after 4,000 cal BP that was largely driven by increased reliance on maize farming.

This study uses isotope and microbotanical data from the analysis of teeth and dental calculus to investigate camelid diet and foddering practices at Quilcapampa (AD 835–900). By providing taxonomically specific evidence of foods consumed, botanical data from dental calculus complement the more general impressions of photosynthetic pathways obtained through isotopic analysis. Results suggest that the camelid diet incorporated maize ( Zea mays ), algarrobo ( Prosopis sp.), potato chuño ( Solanum sp.), and other resources. The life-history profile of one camelid (Individual 3) reveals dietary change from mainly C 3 plants to more C 4 plant contributions as the animal aged. This pattern is supported by carbonate isotope results indicating that this individual spent its youth in the mid-valley ecozone before becoming more mobile later in life. As this life-history example shows, isotopic and microbotanical analyses are complementary approaches, clarifying a pattern of seasonal transhumance that linked the lives of humans and animals along the Middle Horizon (AD 600–1000) caravan networks that crisscrossed the central Andes.

Recent remote sensing research in the Tlalixcoyan basin, Veracruz, has identified patterns of raised fields and public civic-ceremonial plaza groups that suggest a local and decentralized strategy of cooperation to develop hydraulic and agricultural resources. This perspective provides support for Scarborough and Lucero’s (2010) cross-cultural conceptualization of hydraulic strategies in the semi-tropics, but we note some exceptions to their model as well. We conclude based on the remotely sensed data that (1) most of the interconnected field systems are too large or complex for a single family or lineage to have built and maintained alone; (2) the Tlalixcoyan settlement system is divided into clusters that likely represent social groupings akin to administrative districts; (3) each residential cluster possessed its own public civic-ceremonial plaza group; (4) each plaza group could have provided the seat of cooperation in the creation and maintenance of common-pool resources like raised fields; and (5) despite the implication of local hydraulic management within districts, the region as a whole presents a hierarchical settlement distribution with the Tlalixcoyan Monumental Complex at the top. The last two points represent central hypotheses generated from the remote sensing data that will be tested in future field research.

Significance Maize is a global food staple with great economic and cultural importance. Archaeogenomic studies have revealed a process of protracted maize domestication and multiple waves of human-mediated dispersal in the Americas. Maize first arrived in South America as a partial domesticate, where the domestication syndrome became independently fixed and improved varieties developed away from the influence of wild gene flow. We demonstrate that hybrids of some of these improved varieties were likely reintroduced back to Central America. We hypothesize that this backflow of South American genetic material may have contributed to the development of a more productive staple, which was related to the growth and aggregation of human populations, and the formation of more complex social and political structures regionally.

Calibration and analysis of radiocarbon dates from the Orendorf settlement is framed within the broader scope of the regional chronology of the Central Illinois River Valley, building on research presented in Wilson et al. 2018 (journal article published in Southeastern Archaeology).