Originals
Hindcasting global population densities reveals forces enabling the origin of agriculture
Patrick Kavanagh et al.
Nature Human Behaviour, July 2018, Pages 478–484
Abstract:
The development and spread of agriculture changed fundamental characteristics of human societies. However, the degree to which environmental and social conditions enabled the origins of agriculture remains contested. We test three hypothesized links between the environment, population density and the origins of plant and animal domestication, a prerequisite for agriculture: (1) domestication arose as environmental conditions improved and population densities increased (surplus hypothesis); (2) populations needed domestication to overcome deteriorating environmental conditions (necessity hypothesis); (3) factors promoting domestication were distinct in each location (regional uniqueness hypothesis). We overcome previous data limitations with a statistical model, in which environmental, geographic and cultural variables capture 77% of the variation in population density among 220 foraging societies worldwide. We use this model to hindcast potential population densities across the globe from 21,000 to 4,000 years before present. Despite the timing of domestication varying by thousands of years, we show that improving environmental conditions favoured higher local population densities during periods when domestication arose in every known agricultural origin centre. Our results uncover a common, global factor that facilitated one of humanity’s most significant innovations and demonstrate that modelling ancestral demographic changes can illuminate major events deep in human history.
Evidence for close-range hunting by last interglacial Neanderthals
Sabine Gaudzinski-Windheuser et al.
Nature Ecology & Evolution, July 2018, Pages 1087–1092
Abstract:
Animal resources have been part of hominin diets since around 2.5 million years ago, with sharp-edged stone tools facilitating access to carcasses. How exactly hominins acquired animal prey and how hunting strategies varied through time and space is far from clear. The oldest possible hunting weapons known from the archaeological record are 300,000 to 400,000-year-old sharpened wooden staves. These may have been used as throwing and/or close-range thrusting spears, but actual data on how such objects were used are lacking, as unambiguous lesions caused by such weapon-like objects are unknown for most of human prehistory. Here, we report perforations observed on two fallow deer skeletons from Neumark-Nord, Germany, retrieved during excavations of 120,000-year-old lake shore deposits with abundant traces of Neanderthal presence. Detailed studies of the perforations, including micro-computed tomography imaging and ballistic experiments, demonstrate that they resulted from the close-range use of thrusting spears. Such confrontational ways of hunting require close cooperation between participants, and over time may have shaped important aspects of hominin biology and behaviour.
Male and Female Nipples as a Test Case for the Assumption that Functional Features Vary Less than Nonfunctional Byproducts
Ashleigh Kelly et al.
Adaptive Human Behavior and Physiology, forthcoming
Objectives: Evolutionary researchers have sometimes taken findings of low variation in the size or shape of a biological feature to indicate that it is functional and under strong evolutionary selection, and have assumed that high variation implies weak or absent selection and therefore lack of function.
Methods: To test this assumption we compared the size variation (using a mean-adjusted measure of absolute variability) of the functional human female nipple (defined as the nipple-areola complex) with that of the non-functional human male nipple.
Results: We found that female nipples were significantly more variable than male nipples, even after controlling for body mass index, testing-room temperature, bust size in women, and chest size in men.
Conclusions: Morphological variation in a feature should not be used by itself to infer whether or not the feature is functional or under selection.
A Noisy Signal: To what extent are Hadza hunting reputations predictive of actual hunting skills?
Duncan Stibbard-Hawkes, Robert Attenborough & Frank Marlowe
Evolution and Human Behavior, forthcoming
Abstract:
The measurement of hunting ability has been central to several debates about the goals of men’s hunting among the Hadza and other hunter-gatherer populations. Hunting ability has previously been measured indirectly, by weighing the amount of food individuals bring back to camp over an extended period, their central place hunting return rate, and by conducting hunting ability interviews. Despite the centrality of the hunting ability concept, some authors (Hill & Kintigh, 2009) have expressed scepticism that such measures accurately capture individual differences in actual hunting ability. In the current study, we introduce a novel measure of hunting reputation which, unlike previous ones, allows fine-grained distinction between hunters of all reputations. To assess the suitability of this measure as a viable proxy for hunting ability, we address two further questions. First, to what extent do interviewees agree about the hunting ability of their present and former campmates? Second, to what extent does this measure of hunting reputation reflect success in four tasks expected to capture important components of hunting ability? We demonstrate that these measures of hunting reputation appear to reflect variation in these skills. We argue, however, that hunting reputation appears too noisy an index of these skills and, we infer, hunting ability in general for hunting to act, as some have suggested (e.g. Hawkes & Bird, 2002), as an honest signal of cryptic qualities related to hunting ability.
Coalitional Play Fighting and the Evolution of Coalitional Intergroup Aggression
Michelle Scalise Sugiyama et al.
Human Nature, forthcoming
Abstract:
Dyadic play fighting occurs in many species, but only humans are known to engage in coalitional play fighting. Dyadic play fighting is hypothesized to build motor skills involved in actual dyadic fighting; thus, coalitional play fighting may build skills involved in actual coalitional fighting, operationalized as forager lethal raiding. If human psychology includes a motivational component that encourages engagement in this type of play, evidence of this play in forager societies is necessary to determine that it is not an artifact of agricultural or industrial conditions. We examine whether coalitional play fighting appears in the hunter-gatherer record and includes motor skills used in lethal raiding. Using the ethnographic record, we generated a list of motor patterns regularly used in forager warfare. Then, using Murdock’s Ethnographic Atlas, we identified 100 culture clusters containing forager societies and searched the ethnographic records of these societies for descriptions of coalitional play fighting, operationalized as contact games played in teams. Resulting games were coded for the presence of eight motor patterns regularly used in forager lethal raiding. Although play does not tend to be systematically documented in the hunter-gatherer literature, sufficiently detailed descriptions of coalitional play were found for 46 of the 100 culture clusters: all 46 exhibited coalitional play using at least one of the predicted motor patterns; 39 exhibited coalitional play using four or more of the eight predicted motor patterns. These results provide evidence that coalitional play fighting (a) occurs across a diverse range of hunter-gatherer cultures and habitats, (b) regularly recruits motor patterns used in lethal raiding, and (c) is not an artifact of agricultural or industrial life. This is a first step in a new line of research on whether human male psychology includes motivations to engage in play that develops the deployment of coordinated coalitional action involving key motor patterns used in lethal raiding.
Ancient genomes document multiple waves of migration in Southeast Asian prehistory
Mark Lipson et al.
Science, 6 July 2018, Pages 92-95
Abstract:
Southeast Asia is home to rich human genetic and linguistic diversity, but the details of past population movements in the region are not well known. Here, we report genome-wide ancient DNA data from 18 Southeast Asian individuals spanning from the Neolithic period through the Iron Age (4100 to 1700 years ago). Early farmers from Man Bac in Vietnam exhibit a mixture of East Asian (southern Chinese agriculturalist) and deeply diverged eastern Eurasian (hunter-gatherer) ancestry characteristic of Austroasiatic speakers, with similar ancestry as far south as Indonesia providing evidence for an expansive initial spread of Austroasiatic languages. By the Bronze Age, in a parallel pattern to Europe, sites in Vietnam and Myanmar show close connections to present-day majority groups, reflecting substantial additional influxes of migrants.