About

Heather Thakar is an Assistant Professor at Texas A&M University College of Arts and Sciences, where she serves as the Director of the Archaeobotany & Palynology Laboratories and the Radiocarbon & Isotope Preparation Laboratory. Her research focuses on archaeological theory, evolutionary ecology, and the study of foraging and proto-agricultural societies in the New World, particularly in regions such as California, Mexico, Belize, Honduras, and Nicaragua. Thakar's work involves isotope geochemistry, radiocarbon dating, zooMS collagen peptide fingerprinting, archaeobotany, and palynology, with a strong emphasis on understanding human niche construction during the Late Pleistocene and Middle Holocene in Pacific Central America, as well as foodways reconstruction and domestication processes during the Holocene.

Research topics

• Sociology
• Archaeology
• Biology
• Geography
• Forestry
• Mechanical engineering
• Botany
• Engineering
• Demography
• Ecology
• Engineering ethics
• History
• Genetics

Selected publications

• Refining near-infrared spectroscopy for collagen quantification: A new predictive model for archaeological bone

  Journal of Archaeological Science · 2025-12-09 · 1 citations

  articleOpen access

  Collagen is a vital archaeological material, preserving biochemical signatures that provide insights into past environments, diets, and human-animal interactions. However, diagenesis can lead to rapid and inconspicuous collagen degradation. Given the variability in collagen preservation and its significance for analyses such as radiocarbon dating, stable isotope analysis, and ZooMS, researchers have developed prescreening techniques to assess collagen preservation before destructive sampling. Current prescreening approaches, including %N and C:N ratios, typically require sample destruction and access to equipped laboratories. Spectroscopic techniques such as Raman spectroscopy and Fourier Transform Infrared spectroscopy have been explored as alternatives, but they are limited in penetration depth, generalizability (at present at least), and are often still destructive, if minimally. Here, we further develop single-point near-infrared (NIR) spectroscopy as a fully non-destructive, rapid, and field-portable method for prescreening bone for collagen preservation. Unlike FTIR and Raman spectroscopic techniques, NIR light penetrates below the surface of bone, enabling assessment of internal collagen preservation without destructive sample preparation. Using Partial Least Squares Regression (PLSR) and Random Forest (RF) modeling, we trained predictive models on whole bones with known collagen yields and validated the models on an independent archaeological collection. Both PLSR and RF models, when restricted to the 2030–2060 nm range, demonstrate strong and comparable performance while avoiding wavelengths associated with consolidants in our reference library. The models outperform traditional % N-based methods in identifying suitable samples for radiocarbon dating. These models enable the high-throughput screening of large collections of bone, improving sample selection and minimizing unnecessary destructive analysis.

  PublisherDOI

• Early evidence of avocado domestication from El Gigante Rockshelter, Honduras

  Proceedings of the National Academy of Sciences · 2025-03-03 · 3 citations

  articleOpen access

  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.

  PublisherDOI

• Refining Near-Infrared Spectroscopy for Collagen Quantification: A New Predictive Model for Archaeological Bone

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Fishing further inland? The role of the transition to agriculture on fishing practices in the Soconusco region, Mexico

  The Journal of Island and Coastal Archaeology · 2024-06-08

  articleOpen accessSenior author

  In the Soconusco region of Mexico, the abundance of larger-bodied, carnivorous fish decreased relative to smaller-bodied, omnivorous/herbivorous fish between the terminal Late Archaic (4700–4000 BP [2700–2000 BCE]) and late Early Formative (3300–3200 BP [1300–1200 BCE]). The exact reason is unknown, occurring during a time of change when plant-based food production became a larger proportion of the diet and settlement patterns were shifting. Here, we address whether the same diversity of fish harvested during the terminal Late Archaic persisted into the Formative Period and if it reflects a change in where fish were being harvested. Using seven previously identified and published zooarchaeological assemblages dating to between the Middle Archaic and Middle Formative periods, we analyzed changes in diversity (NISP versus NTAXA, evenness, and richness) and habitat exploitation (nestedness and proportion of aquatic environment). We find differences in taxonomic diversity, changes in where fish were harvested along the coast, and the degree of exploitation intensity. Finally, we conclude the Chantuto society may have shifted their focus from marine to more freshwater species in conjunction with early low-level food production and agricultural production. We suggest the shift in focus during the late Early Formative and Middle Formative to estuarine–riverine environments may have occurred in conjunction with agricultural intensification.

  PublisherOA PDFDOI

• Archaeobotanical evidence supports indigenous cucurbit long-term use in the Mesoamerican Neotropics

  Scientific Reports · 2024-05-13 · 2 citations

  articleOpen access

  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.

  PublisherOA PDFDOI

• Current and Future Applications of Genetic, Archaeological, and Ethnobotanical Data to Uncovering Avocado Domestication

  Ethnobiology Letters · 2024-09-16

  articleOpen accessSenior author

  The domestication of fruit trees is a topic of increasing significance in anthropological research. The avocado is a perennial fruit domesticated in Central America with a complex history of management and dispersal since the arrival of humans in the New World. Archaeological data illustrates the avocado’s domestication from wild to cultivar forms throughout the Holocene, while genetic and ethnobotanical evidence provide insights into ancient avocado cultivation patterns. It is only through the combined application of all three lines of evidence that we may fully understand the dynamic origins of this essential fruit.

  PublisherOA PDFDOI

• Working Ethically with Ancient DNA from Composites in the United States

  Advances in Archaeological Practice · 2024 · 6 citations

  • Sociology
  • Archaeology
  • Engineering ethics

  Abstract This article discusses ethical frameworks for planning and implementing composite research in the United States. Composites, defined here as archaeological materials with multiple genetic sources, include materials such as sediment, coprolites, birch pitch, and dental calculus. Although composites are increasingly used in genetic research, the ethical considerations of their use in ancient DNA studies have not been widely discussed. Here, we consider how composites’ compositions, contexts, and potential to act as proxies can affect research plans and offer an overview of the primary ethical concerns of ancient DNA research. It is our view that ethical principles established for analyses of Ancestral remains and related materials can be used to inform research plans when working with composite evidence. This work also provides a guide to archaeologists unfamiliar with genetics analyses in planning research when using composite evidence from the United States with a focus on collaboration, having a clear research plan, and using lab methods that provide the desired data with minimal destruction. Following the principles discussed in this article and others allows for engaging in composite research while creating and maintaining positive relationships with stakeholders.

  PublisherOA PDFDOI

• Trans–Holocene Bayesian chronology for tree and field crop use from El Gigante rockshelter, Honduras

  PLoS ONE · 2023 · 7 citations

  • Archaeology
  • Geography
  • Biology

  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.

  PublisherOA PDFDOI

• Archaeological Central American maize genomes suggest ancient gene flow from South America

  Proceedings of the National Academy of Sciences · 2020 · 82 citations

  • Sociology
  • Biology
  • Geography

  ) domestication began in southwestern Mexico ∼9,000 calendar years before present (cal. BP) and humans dispersed this important grain to South America by at least 7,000 cal. BP as a partial domesticate. South America served as a secondary improvement center where the domestication syndrome became fixed and new lineages emerged in parallel with similar processes in Mesoamerica. Later, Indigenous cultivators carried a second major wave of maize southward from Mesoamerica, but it has been unclear until now whether the deeply divergent maize lineages underwent any subsequent gene flow between these regions. Here we report ancient maize genomes (2,300-1,900 cal. BP) from El Gigante rock shelter, Honduras, that are closely related to ancient and modern maize from South America. Our findings suggest that the second wave of maize brought into South America hybridized with long-established landraces from the first wave, and that some of the resulting newly admixed lineages were then reintroduced to Central America. Direct radiocarbon dates and cob morphological data from the rock shelter suggest that more productive maize varieties developed between 4,300 and 2,500 cal. BP. We hypothesize that the influx of maize from South America into Central America may have been an important source of genetic diversity as maize was becoming a staple grain in Central and Mesoamerica.

  PublisherOA PDFDOI

• Archaeological assessment reveals Earth’s early transformation through land use

  Science · 2019-08-29 · 588 citations

  articleOpen access

  Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth's transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon.

  PublisherOA PDFDOI

Frequent coauthors

• Kenneth Hirth

  Pennsylvania State University

  5 shared

• Logan Kistler

  National Museum of Natural History

  5 shared

• Alejandra I. Domic

  Pennsylvania State University

  4 shared

• Amber M. VanDerwarker

  University of California, Santa Barbara

  4 shared

• Thomas K. Harper

  Pennsylvania State University

  4 shared

• Douglas J. Kennett

  4 shared

• Timothy E. Scheffler

  Volcano Corporation (United States)

  3 shared

• Brendan J. Culleton

  Pennsylvania State University

  2 shared

Labs

• Archaeobotany & Palynology LaboratoriesPI

Awards & honors

• NSF Archaeology Program Collaborative Research Grant BCS-202…
• NSF Archaeology Program Collaborative Research Grant BCS-175…