Legacy Systems
Perceptual Grouping Explains Similarities in Constellations Across Cultures
Charles Kemp et al.
Psychological Science, forthcoming
Abstract:
Cultures around the world organize stars into constellations, or asterisms, and these groupings are often considered to be arbitrary and culture specific. Yet there are striking similarities in asterisms across cultures, and groupings such as Orion, the Big Dipper, the Pleiades, and the Southern Cross are widely recognized across many different cultures. Psychologists have informally suggested that these shared patterns are explained by Gestalt laws of grouping, but there have been no systematic attempts to catalog asterisms that recur across cultures or to explain the perceptual basis of these groupings. Here, we compiled data from 27 cultures around the world and found that a simple computational model of perceptual grouping accounts for many of the recurring cross-cultural asterisms. Our results suggest that basic perceptual principles account for more of the structure of asterisms across cultures than previously acknowledged and highlight ways in which specific cultures depart from this shared baseline.
The tempo of the Iberian megalithic rituals in the European context: The cemetery of Panoría
Gonzalo Aranda Jiménez et al.
Journal of Archaeological Science, forthcoming
Abstract:
Our ability to build precise narratives regarding megalithic societies largely depends on the chronology of the multi-ritual events that usually shaped these complex sites. The cemetery of Panoría offers an excellent opportunity for exploring ritual complexity in Iberia through radiocarbon chronology, as four of the nine recently excavated dolmens are remarkably well preserved. For this purpose, seventy-three radiocarbon dates were obtained and analysed within a Bayesian framework. The resulting refined chronology has led us to three main conclusions: i) in all tombs, the second half of the 4th millennium cal BC was an intensive but brief period of funerary depositions, probably over three to six generations; ii) after a long hiatus, most of the dolmens were reused in the 25th and 21st centuries cal BC during even shorter periods, spanning just a few decades and approximately one to four generations; and (iii) long after the funerary rituals had ended in the 21st century, the memory of the cemetery was revived in Late Antiquity. These short, punctuated periods of use are highly consistent with those seen in a growing number of European megalithic monuments. From Britain to Iberia, a pattern of short spans of use is dramatically changing our perception of the social and political roles of these complex monuments.
Hunter-gatherer genomes reveal diverse demographic trajectories during the rise of farming in Eastern Africa
Shyamalika Gopalan et al.
Current Biology, forthcoming
Abstract:
The fate of hunting and gathering populations following the rise of agriculture and pastoralism remains a topic of debate in the study of human prehistory. Studies of ancient and modern genomes have found that autochthonous groups were largely replaced by expanding farmer populations with varying levels of gene flow, a characterization that is influenced by the almost universal focus on the European Neolithic. We sought to understand the demographic impact of an ongoing cultural transition to farming in Southwest Ethiopia, one of the last regions in Africa to experience such shifts. Importantly, Southwest Ethiopia is home to several of the world’s remaining hunter-gatherer groups, including the Chabu people, who are currently transitioning away from their traditional mode of subsistence. We generated genome-wide data from the Chabu and four neighboring populations, the Majang, Shekkacho, Bench, and Sheko, to characterize their genetic ancestry and estimate their effective population sizes over the last 60 generations. We show that the Chabu are a distinct population closely related to ancient people who occupied Southwest Ethiopia >4,500 years ago. Furthermore, the Chabu are undergoing a severe population bottleneck, which began approximately 1,400 years ago. By analyzing eleven Eastern African populations, we find evidence for divergent demographic trajectories among hunter-gatherer-descendant groups. Our results illustrate that although foragers respond to encroaching agriculture and pastoralism with multiple strategies, including cultural adoption of agropastoralism, gene flow, and economic specialization, they often face population decline.
The evolution of de novo human-specific microRNA genes on chromosome 21
Hunter Johnson et al.
American Journal of Biological Anthropology, forthcoming
Abstract:
The genetic basis of human uniqueness remains one of the most enduring mysteries in biological anthropology. The goal of this research project was to identify, characterize, and infer the origin and function of novel elements in the human genome that are not functionally shared with other apes. Our approach toward this goal was to utilize a variety of genome alignment tools to discover islands of non-conserved DNA sequences, followed by theoretical and computational analysis of those regions using synteny sequence analysis. We discovered families of microRNA genes on human chromosome 21 with no detectable orthologs in the other African apes. We then developed a working model of their origin through repeated rounds of segmental duplication occurring within an array of rRNA genes. Target prediction reveals potential roles for these microRNA genes in the embryonic development of the central nervous system. We conclude that the 21p11 region of human chromosome 21 has undergone segmental duplication events that generated de novo microRNA genes from within a field of rRNA genes. These microRNA genes may have played a role in the unique evolutionary trajectory of the human lineage through their modulation of genes involved in embryonic development.
Evidence for a mid-Holocene drowning from the Atacama Desert coast of Chile
Pedro Andrade et al.
Journal of Archaeological Science, forthcoming
Abstract:
Coastal archaeological communities were exposed to numerous risks associated with living in their liminal environment. Many of the problems faced by these populations have been recorded and interpreted through their skeletal remains, but death by drowning in saltwater is not easy to recognise and as such is invariably either ignored, inferred, or discounted as a possible cause of death. Here we develop and test an enhanced microscopic marine fingerprinting methodology to determine the death by drowning of a ∼5000 year old coastal hunter-gatherer from the hyperarid coast of northern Chile. Through the application of this forensic method, we were able to detect the presence of a range of exogenous microscopic material that allows us to postulate his death because of drowning in the nearshore environment. This methodology has the potential to greatly enrich our understanding of past human-environment interactions not only in northern Chile but also around the world's coastlines. How pervasive was drowning in prehistory particularly along an active, tectonic margin exposed to palaeotsunamis and extreme ENSO-related palaeostorms?