Domestication as innovation : the entanglement of techniques, technology and chance in the domestication of cereal crops

The origins of agriculture involved pathways of domestication in which human behaviours and plant genetic adaptations were entangled. These changes resulted in consequences that were unintended at the start of the process. This paper highlights some of the key innovations in human behaviours, such as soil preparation, harvesting and threshing, and how these were coupled with genetic ‘innovations’ within plant populations. We identify a number of ‘traps’ for early cultivators, including the needs for extra labour expenditure on crop-processing and soil fertility maintenance, but also linked gains in terms of potential crop yields. Compilations of quantitative data across a few different crops for the traits of nonshattering and seed size are discussed in terms of the apparently slow process of domestication, and parallels and differences between different regional pathways are identified. We highlight the need to bridge the gap between a Neolithic archaeobotanical focus on domestication and a focus of later periods on crop-processing activities and labour organization. In addition, archaeobotanical data provide a basis for rethinking previous assumptions about how plant genetic data should be related to the origins of agriculture and we contrast two alternative hypotheses: gradual evolution with low selection pressure versus metastable equilibrium that prolonged the persistence of ‘semi-domesticated’ populations. Our revised understanding of the innovations involved in plant domestication highlight the need for new approaches to collecting, modelling and integrating genetic data and archaeobotanical evidence

Studying the relationship between past people and their environments

AGU Chapman Conference on Climates, Past Landscapes, and Civilizations; Santa Fe, New Mexico, 21–25 March 2011; The fortunes of human societies are intimately linked to the environments that sustain them. This has been true from the first emergence of human ancestors through to the present day. An AGU Chapman Conference was held to discuss the relationship between past people and their environments. Participants examined the state of the field, debated issues of contention, and formulated ways that such cross-disciplinary research can progress. Scientists' increasing ability to generate high-resolution climate records has proliferated studies that link the rise and fall of cultures to climate change. This meeting brought together scholars from across the divide between Earth sciences and archaeology to derive a deeper understanding of how humans have reacted to and shaped the changing environment.Anthropolog

The Rice Paradox: Multiple Origins but Single Domestication in Asian Rice

The origin of domesticated Asian rice (Oryza sativa) has been a contentious topic, with conflicting evidence for either single or multiple domestication of this key crop species. We examined the evolutionary history of domesticated rice by analyzing de novo assembled genomes from domesticated rice and its wild progenitors. Our results indicate multiple origins, where each domesticated rice subpopulation (japonica, indica, and aus) arose separately from progenitor O. rufipogon and/or O. nivara. Coalescence-based modeling of demographic parameters estimate that the first domesticated rice population to split off from O. rufipogon was O. sativa ssp. japonica, occurring at ∼13.1–24.1 ka, which is an order of magnitude older then the earliest archeological date of domestication. This date is consistent, however, with the expansion of O. rufipogon populations after the Last Glacial Maximum ∼18 ka and archeological evidence for early wild rice management in China. We also show that there is significant gene flow from japonica to both indica (∼17%) and aus (∼15%), which led to the transfer of domestication alleles from early-domesticated japonica to proto-indica and proto-aus populations. Our results provide support for a model in which different rice subspecies had separate origins, but that de novo domestication occurred only once, in O. sativa ssp. japonica, and introgressive hybridization from early japonica to proto-indica and proto-aus led to domesticated indica and aus rice

Holocene evolution in weathering and erosion patterns in the Pearl River delta

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013); 2349–2368, doi:10.1002/ggge.20166.Sediments in the Pearl River delta have the potential to record the weathering response of this river basin to climate change since 9.5 ka, most notably weakening of the Asian monsoon since the Early Holocene (∼8 ka). Cores from the Pearl River delta show a clear temporal evolution of weathering intensity, as measured by K/Al, K/Rb, and clay mineralogy, that shows deposition of less weathered sediment at a time of weakening monsoon rainfall in the Early-Mid Holocene (6.0–2.5 ka). This may reflect an immediate response to a less humid climate, or more likely reduced reworking of older deposits from river terraces as the monsoon weakened. Human settlement of the Pearl River basin may have had a major impact on landscape and erosion as a result of the establishment of widespread agriculture. After around 2.5 ka weathering intensity sharply increased, despite limited change in the monsoon, but at a time when anthropogenic pollutants (e.g., Cu, Zn, and Pb) increased and when the flora of the basin changed. 87Sr/86Sr covaries with these other proxies but is also partly influenced by the presence of carbonate. The sediments in the modern Pearl River are even more weathered than the youngest material from the delta cores. We infer that the spread of farming into the Pearl River basin around 2.7 ka was followed by a widespread reworking of old, weathered soils after 2.5 ka, and large-scale disruption of the river system that was advanced by 2.0 ka.We acknowledge financial support from the Swire Educational Trust and South China Sea Institute of Oceanology PhD Funding (Grant No. MSGL09-06).2014-01-2

Rolling friction of a viscous sphere on a hard plane

A first-principle continuum-mechanics expression for the rolling friction coefficient is obtained for the rolling motion of a viscoelastic sphere on a hard plane. It relates the friction coefficient to the viscous and elastic constants of the sphere material. The relation obtained refers to the case when the deformation of the sphere $\xi$ is small, the velocity of the sphere $V$ is much less than the speed of sound in the material and when the characteristic time $\xi/V$ is much larger than the dissipative relaxation times of the viscoelastic material. To our knowledge this is the first ``first-principle'' expression of the rolling friction coefficient which does not contain empirical parameters.Comment: 6 pages, 2 figure

Reply to Ellis et al.: human niche construction and evolutionary theory

We are pleased Ellis et al. found value in our recent synthesis of the deep history of human impacts on global ecosystems and agree that our paper should influence the current debate on if and how an Anthropocene epoch is defined. We also agree that the ecological consequences of human niche construction have profound and growing effects on the evolutionary trajectories of humans and other species living within human-altered ecosystems. Niche construction theory (NCT) provides an explicit framework for linking evolutionary and ecological processes into a coherent theory of biological evolution. Of special appeal to us as archaeologists is that NCT bridges biological and cultural evolution by including human culture and social learning within the mechanisms of evolutionary change, allowing scientists to address issues at the interface of human and natural systems. Some of us have contributed significantly to human NCT, addressing some of the very issues raised by Ellis et al. Finally, we agree that human transformations of ecosystems are inherently social processes—clearly humans are intensely social organisms—and that such processes result from long-term melding of biological and cultural evolution

Reply to Westaway and Lyman: emus, dingoes, and archaeology’s role in conservation biology

In a curious comment on our PNAS Perspective, Westaway and Lyman offer two Australian zooarchaeological case studies—one involving eggshells and the other dingoes—that they argue undercut one of our main points: that archaeological data and deep time perspectives have much to offer conservation biology. Neither example provides a specific substantive critique of our perspective: there are no dingoes in our article, no eggshells, and we mention the long and rich record of human management and alteration of Australian environments only briefly. Nor do we suggest that all archaeological assemblages can effectively inform current conservation biology efforts. Such datasets obviously vary in their quality and potential applicability to modern situations. When considered more closely, both of Westaway and Lyman’s case studies underscore rather than undercut the importance of archaeological and paleoecological data in conservation biology initiatives

Tarantino the cartoonist

In cinema it is not uncommon to see the interrelation of animation and live action but, despite this, the ascription of characteristics of one medium onto the other has been largely one-dimensional: live action upon animation. The films of Quentin Tarantino, however, illustrate an attribution of a cartoon-like aesthetic in live-action sequences, which the author subsequently terms `cartoonism'. `Cartoonism' and its development have been highlighted in Tarantino's work, showing his continual desire to realize this aesthetic in his own work whilst, ironically, only fully achieving this aesthetic in another's film. The conclusions are illuminating with respect to Tarantino's filmic politics and provide a potential mode of inquiry within film theory

Neoglacial climate anomalies and the Harappan metamorphosis

Climate exerted constraints on the growth and decline of past human societies but our knowledge of temporal and spatial climatic patterns is often too restricted to address causal connections. At a global scale, the inter-hemispheric thermal balance provides an emergent framework for understanding regional Holocene climate variability. As the thermal balance adjusted to gradual changes in the seasonality of insolation, the Intertropical Convergence Zone migrated southward accompanied by a weakening of the Indian summer monsoon. Superimposed on this trend, anomalies such as the Little Ice Age point to asymmetric changes in the extratropics of either hemisphere. Here we present a reconstruction of the Indian winter monsoon in the Arabian Sea for the last 6000 years based on paleobiological records in sediments from the continental margin of Pakistan at two levels of ecological complexity: Sedimentary ancient DNA reflecting water column environmental states and planktonic foraminifers sensitive to winter conditions. We show that strong winter monsoons between ca. 4500 and 3000 years ago occurred during a period characterized by a series of weak interhemispheric temperature contrast intervals, which we identify as the early neoglacial anomalies (ENA). The strong winter monsoons during ENA were accompanied by changes in wind and precipitation patterns that are particularly evident across the eastern Northern Hemisphere and tropics. This coordinated climate reorganization may have helped trigger the metamorphosis of the urban Harappan civilization into a rural society through a push-pull migration from summer flood-deficient river valleys to the Himalayan piedmont plains with augmented winter rains. The decline in the winter monsoon between 3300 and 3000 years ago at the end of ENA could have played a role in the demise of the rural late Harappans during that time as the first Iron Age culture established itself on the Ghaggar-Hakra interfluve. Finally, we speculate that time-transgressive land cover changes due to aridification of the tropics may have led to a generalized instability of the global climate during ENA at the transition from the warmer Holocene thermal maximum to the cooler Neoglacial

Resonance locking in giant planets indicated by the rapid orbital expansion of Titan

Saturn is orbited by dozens of moons, and the intricate dynamics of this complex system provide clues about its formation and evolution. Tidal friction within Saturn causes its moons to migrate outwards, driving them into orbital resonances that pump their eccen- tricities or inclinations, which in turn leads to tidal heating of the moons. However, in gi- ant planets, the dissipative processes that determine the tidal migration timescale remain poorly understood. Standard theories suggest an orbital expansion rate inversely pro- portional to the power 11/2 in distance1, implying negligible migration for outer moons such as Saturn’s largest moon, Titan. Here, we use two independent measurements ob- tained with the Cassini spacecraft to measure Titan’s orbital expansion rate. We find Titan rapidly migrates away from Saturn on a timescale of roughly 10 Gyr, corresponding to a tidal quality factor of Saturn of Q ≃ 100, which is more than a hundred times smaller than most expectations. Our results for Titan and five other moons agree with the predic- tions of a resonance locking tidal theory2, sustained by excitation of inertial waves inside the planet. The associated tidal expansion is only weakly sensitive to orbital distance, motivating a revision of the evolutionary history of Saturn’s moon system. In particular, it suggests Titan formed significantly closer to Saturn and has migrated outward to its current position