Archaeology, climate, and global change in the Age of Humans

Climate and cultural evolution drove Holocene cropland change in the Huai River Valley, China

As an important way of maximizing land productivity by growing more than one crop type in the same field, mixed cropping has been an effective option for sustaining population growth under different climatic conditions since prehistoric period. We used a combination of archaeological data and an improved prehistoric land use model (PLUM) to quantitatively reconstruct spatiotemporal changes in cropland types and areas in the Huai River Valley of China, a core region of mixed cropping during the Holocene. The total cropland area increased more than 25 times during 8-2 ka BP, with northward expansion of rice-dominated cultivation during 5-4 ka BP and southward expansion of dry-dominated cultivation after 4 ka BP. Temperature and precipitation determined cropland types distribution, while that of cropland area was controlled by cultural development. The interplay between past climate, culture, and cultivation potentially provides useful insights into mitigating future population pressures with climate change.

The human side of biodiversity: coevolution of the human niche, palaeo-synanthropy and ecosystem complexity in the deep human past

Today's biodiversity crisis fundamentally threatens the habitability of the planet, thus ranking among the primary human challenges of our time. Much emphasis is currently placed on the loss of biodiversity in the Anthropocene, yet these debates often portray biodiversity as a purely natural phenomenon without much consideration of its human dimensions and frequently lack long-term vistas. This paper offers a deep-time perspective on the key role of the evolving human niche in ecosystem functioning and biodiversity dynamics. We summarize research on past hunter-gatherer ecosystem contributions and argue that human-environment feedback systems with important biodiversity consequences are probably a recurrent feature of the Late Pleistocene, perhaps with even deeper roots. We update current understandings of the human niche in this light and suggest that the formation of palaeo-synanthropic niches in other animals proffers a powerful model system to investigate recursive interactions of foragers and ecosystems. Archaeology holds important knowledge here and shows that ecosystem contributions vary greatly in relation to different human lifeways, some of which are lost today. We therefore recommend paying more attention to the intricate relationship between biodiversity and cultural diversity, contending that promotion of the former depends on fostering the latter. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Climate change adaptation needs a science of culture

There is global consensus that we must immediately prioritize climate change adaptation-change in response to or anticipation of risks from climate change. Some researchers and policymakers urge 'transformative change', a complete break from past practices, yet report having little data on whether new practices reduce the risks communities face, even over the short term. However, researchers have some leads: human communities have long generated solutions to changing climate, and scientists who study culture have examples of effective and persistent solutions. This theme issue discusses cultural adaptation to climate change, and in this paper, we review how processes of biological adaptation, including innovation, modification, selective retention and transmission, shape the landscapes decision-makers care about-from which solutions emerge in communities, to the spread of effective adaptations, to regional or global collective action. We introduce a comprehensive portal of data and models on cultural adaptation to climate change, and we outline ways forward. This article is part of the theme issue 'Climate change adaptation needs a science of culture'.

A Tough Hydrogel Adhesive for the Repair of Archeological Pottery

Pottery is the oldest art and plays a landmark role in human civilization. The repair of ceramic relics often uses acrylic resins and cyanoacrylate adhesives. However, existing adhesives often take hours to get cured, and wet adhesion is not possible. We herein propose a redox initiator-triggered hydrogel adhesive, of which robust (∼700 J m^-2) and wet adhesion with potsherds can be achieved within a few seconds. The high toughness lies in the self-limited delocalized rupture of the porous interface, and the wet adhesion is due to the hydrophilic precursor and its free radical polymerization. The hydrogel adhesive also exhibits high aging resistance for stable preservation of ∼400 annuals. We have applied the adhesive to the restoration of artifacts excavated from Yinxu, Anyang (∼1300 BC) and the Xia Jiao Shan site (∼4000 BC, Neolithic), and the adhesive is expected to be extended to applications beyond archeology.

Climate and vegetation and their impact on stable C and N isotope ratios in bat guano

Cave guano deposits represent a relatively untapped paleoecological archive that can provide information about past vegetation, climate, and bat diet over several millennia. Recent research suggests that carbon isotope values (δ13C) measured in guano accumulations from insectivorous bats reflect the relative abundance of C3 and C4 plants on the landscape while nitrogen isotope values (δ15N) may reflect precipitation amount. Together, these proxies can provide useful information for restoration practitioners seeking to understand how plant species composition has changed over time in relation to climate and land use. To better calibrate these proxies for use in restoration, we compared instrumental records of precipitation and satellite imagery of vegetation with isotope values measured in modern bat guano from Mary Lawson Cave, a large limestone cavern located in central Missouri. Mary Lawson Cave hosts a maternity colony of insectivorous gray bats (Myotis grisescens), and as such, contains significant guano accumulations. In the fall of 2018, we collected a 60 cm long guano core that dates to 1999 cal AD at its base. Guano core δ13C values decrease from the base toward the surface (from ~-26 to -27‰) whereas δ15N values increase toward the surface even after accounting for ammonia volatilization (from ~3 to 5‰). Presently, the landscape around Mary Lawson Cave is dominated by a deciduous forest and pasture. Given that the land cover has changed very little over this period, the decline in δ13C values toward the present likely reflects a shift in land management on farms and/or increases in invasive C3 species. Rainfall amounts from nearby Lebanon, Missouri, are significantly positively correlated with guano δ15N values, a relationship that is notably opposite that observed previously in soil and plants. We argue that heavy fertilizer application and significant grazing intensity could lead to the accumulation of large pools of excess labile nitrogen which would be vulnerable to leaching during precipitation events. The relationship between guano δ15N values and precipitation may differ for materials from less agriculturally impacted locations or periods and should be extended into the past with caution.

Towards a science of archaeoecology

We propose defining a field of research called 'archaeoecology' that examines the past ~60 000 years of interactions between humans and ecosystems to better understand the human place within them. Archaeoecology explicitly integrates questions, data, and approaches from archaeology and ecology, and coalesces recent and future studies that demonstrate the usefulness of integrating archaeological, environmental, and ecological data for understanding the past. Defining a subfield of archaeoecology, much as the related fields of environmental archaeology and palaeoecology have emerged as distinct areas of research, provides a clear intellectual context for helping us to understand the trajectory of human-ecosystem interactions in the past, during the present, and into the future.

Quinoa, potatoes, and llamas fueled emergent social complexity in the Lake Titicaca Basin of the Andes

The Lake Titicaca basin was one of the major centers for cultural development in the ancient world. This lacustrine environment is unique in the high, dry Andean altiplano, and its aquatic and terrestrial resources are thought to have contributed to the florescence of complex societies in this region. Nevertheless, it remains unclear to what extent local aquatic resources, particularly fish, and the introduced crop, maize, which can be grown in regions along the lakeshores, contributed to facilitating sustained food production and population growth, which underpinned increasing social political complexity starting in the Formative Period (1400 BCE to 500 CE) and culminating with the Tiwanaku state (500 to 1100 CE). Here, we present direct dietary evidence from stable isotope analysis of human skeletal remains spanning over two millennia, together with faunal and floral reference materials, to reconstruct foodways and ecological interactions in southern Lake Titicaca over time. Bulk stable isotope analysis, coupled with compound-specific amino acid stable isotope analysis, allows better discrimination between resources consumed across aquatic and terrestrial environments. Together, this evidence demonstrates that human diets predominantly relied on C₃ plants, particularly quinoa and tubers, along with terrestrial animals, notably domestic camelids. Surprisingly, fish were not a significant source of animal protein, but a slight increase in C₄ plant consumption verifies the increasing importance of maize in the Middle Horizon. These results underscore the primary role of local terrestrial food resources in securing a nutritious diet that allowed for sustained population growth, even in the face of documented climate and political change across these periods.

Resistance and Care in the Time of COVID-19: Archaeology in 2020

The COVID-19 pandemic offered humanity a portal through which we could break with the past and imagine our world anew. This article reviews how over the course of 2020, a series of intersecting crises at the nexus of racism, settler colonialism, climate change, and sexual harassment have prompted acts of resistance and care in the field of archaeology. Throughout the article, we provide concrete suggestions as to how we can continue the work of movements begun over the course of the past year to improve dynamics within our field and use the lessons from our field to improve life for all people in the world and for our planet. [resistance, care, COVID-19, 2020, climate change, #MeToo, restorative justice].

Transgressing Time: Archaeological Evidence in/of the Anthropocene

Archaeological evidence of human-influenced transformations of physical strata and the Earth system provides strong support to the broad concept of the Anthropocene, yet it also presents a powerful material challenge to some of its most entrenched assumptions. This substantial and growing body of time-transgressive evidence has the potential to radically alter the concept from the ground up and to provide a literal ground on which interdisciplinary collaboration among the natural sciences, social sciences, and humanities can take place.

Remote Sensing Reveals Lasting Legacies of Land-Use by Small-Scale Foraging Communities in the Southwestern Indian Ocean

Archaeologists interested in the evolution of anthropogenic landscapes have productively adopted Niche Construction Theory (NCT), in order to assess long-term legacies of human-environment interactions. Applications of NCT have especially been used to elucidate co-evolutionary dynamics in agricultural and pastoral systems. Meanwhile, foraging and/or highly mobile small-scale communities, often thought of as less intensive in terms of land-use than agropastoral economies, have received less theoretical and analytical attention from a landscape perspective. Here we address this lacuna by contributing a novel remote sensing approach for investigating legacies of human-environment interaction on landscapes that have a long history of co-evolution with highly mobile foraging communities. Our study is centered on coastal southwest Madagascar, a region inhabited by foraging and fishing communities for close to two millennia. Despite significant environmental changes in southwest Madagascar’s environment following human settlement, including a wave of faunal extinctions, little is known about the scale, pace and nature of anthropogenic landscape modification. Archaeological deposits in this area generally bear ephemeral traces of past human activity and do not exhibit readily visible signatures of intensive land-use and landscape modification (e.g., agricultural modifications, monumental architecture, etc.). In this paper we use high-resolution satellite imagery and vegetative indices to reveal a legacy of human-landscape co-evolution by comparing the characteristics – vegetative productivity and geochemical properties – of archaeological sites to those of locations with no documented archaeological materials. Then, we use a random forest (RF) algorithm and spatial statistics to quantify the extent of archaeological activity and use this analysis to contextualize modern-day human-environment dynamics. Our results demonstrate that coastal foraging communities in southwest Madagascar over the past 1,000 years have extensively altered the landscape. Our study thus expands the temporal and spatial scales at which we can evaluate human-environment dynamics on Madagascar, providing new opportunities to study early periods of the island’s human history when mobile foraging communities were the dominant drivers of landscape change.

Conservation of Earth's biodiversity is embedded in Indigenous fire stewardship

Large and severe wildfires are becoming increasingly common worldwide and are having extraordinary impacts on people and the species and ecosystems on which they depend. Indigenous peoples comprise only 5% of the world’s population but protect approximately 85% of the world’s biodiversity through stewardship of Indigenous-managed lands. Much of this is attributed to long-term and widespread relationships with and dependence on fire, which has been applied as a tool for managing landscapes for millennia. Fortunately, the revitalization of Indigenous fire stewardship is demonstrating the value of routinely applying controlled fire to adapt to changing environments while promoting desired landscapes, habitats, and species and supporting subsistence practices and livelihoods.

Increasingly, severe wildfires have led to declines in biodiversity across all of Earth’s vegetated biomes [D. B. McWethy et al., Nat. Sustain. 2, 797–804 (2019)]. Unfortunately, the displacement of Indigenous peoples and place-based societies that rely on and routinely practice fire stewardship has resulted in significant declines in biodiversity and the functional roles of people in shaping pyrodiverse systems [R. Bliege Bird et al., Proc. Natl. Acad. Sci. U.S.A. 117, 12904–12914 (2020)]. With the aim of assessing the impacts of Indigenous fire stewardship on biodiversity and species function across Earth’s major terrestrial biomes, we conducted a review of relevant primary data papers published from 1900 to present. We examined how the frequency, seasonality, and severity of human-ignited fires can improve or reduce reported metrics of biodiversity and habitat heterogeneity as well as changes to species composition across a range of taxa and spatial and temporal scales. A total of 79% of applicable studies reported increases in biodiversity as a result of fire stewardship, and 63% concluded that habitat heterogeneity was increased by the use of fire. All studies reported that fire stewardship occurred outside of the window of uncontrollable fire activity, and plants (woody and nonwoody vegetation) were the most intensively studied life forms. Three studies reported declines in biodiversity associated with increases in the use of high-severity fire as a result of the disruption of Indigenous-controlled fire regimes with the onset of colonization. Supporting Indigenous-led fire stewardship can assist with reviving important cultural practices while protecting human communities from increasingly severe wildfires, enhancing biodiversity, and increasing ecosystem heterogeneity.

The archaeology of climate change: The case for cultural diversity

Anthropogenic climate change is currently driving environmental transformation on a scale and at a pace that exceeds historical records. This represents an undeniably serious challenge to existing social, political, and economic systems. Humans have successfully faced similar challenges in the past, however. The archaeological record and Earth archives offer rare opportunities to observe the complex interaction between environmental and human systems under different climate regimes and at different spatial and temporal scales. The archaeology of climate change offers opportunities to identify the factors that promoted human resilience in the past and apply the knowledge gained to the present, contributing a much-needed, long-term perspective to climate research. One of the strengths of the archaeological record is the cultural diversity it encompasses, which offers alternatives to the solutions proposed from within the Western agro-industrial complex, which might not be viable cross-culturally. While contemporary climate discourse focuses on the importance of biodiversity, we highlight the importance of cultural diversity as a source of resilience.

Contributions of evolutionary anthropology to understanding climate-induced human migration

Humans are able to thrive in a multitude of ecological and social environments, including varied environments over an individual lifetime. Migration-leaving one place of residence for another-is a central feature of many people's life histories, and environmental change goes hand-in-hand with migration, both in terms of cause and consequence. Climate change has amplified this connection between environment and migration, with the potential to profoundly impact millions of lives. Although climate-induced migration has been at the forefront of other disciplines in the social sciences, evolutionary anthropologists (EAs) have given it little attention. In this paper we draw upon existing literature and contribute our EA perspective to present a framework for analyzing climate-induced migration that utilizes theoretical approaches from a variety of social science disciplines. We focus on three overlapping dimensions-time, space, and severity-relevant to understanding the impact of climate change on human migration. We apply this framework to case studies from North America of people impacted by climate change and extreme weather events, including hurricanes, droughts, rising sea-levels, and wildfires. We also consider how access to both economic and social resources influence decisions regarding migration. Research focused on climate-induced human migration can benefit equally from the addition of EA perspectives and a more interdisciplinary theoretical approach.

Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island)

Examining how past human populations responded to environmental and climatic changes is a central focus of the historical sciences. The use of summed probability distributions (SPD) of radiocarbon dates as a proxy for estimating relative population sizes provides a widely applicable method in this research area. Paleodemographic reconstructions and modeling with SPDs, however, are stymied by a lack of accepted methods for model fitting, tools for assessing the demographic impact of environmental or climatic variables, and a means for formal multi-model comparison. These deficiencies severely limit our ability to reliably resolve crucial questions of past human-environment interactions. We propose a solution using Approximate Bayesian Computation (ABC) to fit complex demographic models to observed SPDs. Using a case study from Rapa Nui (Easter Island), a location that has long been the focus of debate regarding the impact of environmental and climatic changes on its human population, we find that past populations were resilient to environmental and climatic challenges. Our findings support a growing body of evidence showing stable and sustainable communities on the island. The ABC framework offers a novel approach for exploring regions and time periods where questions of climate-induced demographic and cultural change remain unresolved.

Summed probability distributions of radiocarbon dates can be used to estimate past demography, but methods to test for associations with environmental change are lacking. Here, DiNapoli et al. propose an approach using Approximate Bayesian Computation and illustrate it in a case study of Rapa Nui.

Mobilizing the past to shape a better Anthropocene

As our planet emerges into a new epoch in which humans dominate the Earth system, it is imperative that societies initiate a new phase of responsible environmental stewardship. Here we argue that information from the past has a valuable role to play in enhancing the sustainability and resilience of our societies. We highlight the ways that past data can be mobilized for a variety of efforts, from supporting conservation to increasing agricultural sustainability and food security. At a practical level, solutions from the past often do not require fossil fuels, can be locally run and managed, and have been tested over the long term. Past failures reveal non-viable solutions and expose vulnerabilities. To more effectively leverage increasing knowledge about the past, we advocate greater cross-disciplinary collaboration, systematic engagement with stakeholders and policymakers, and approaches that bring together the best of the past with the cutting-edge technologies and solutions of tomorrow.