Think back
Maternal investment, life histories and the evolution of brain structure in primates
Lauren Powell, Robert Barton & Sally Street
Proceedings of the Royal Society: Biological Sciences, 18 September 2019
Abstract:
Life history is a robust correlate of relative brain size: larger-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. The cognitive buffer hypothesis (CBH) proposes an adaptive explanation for this relationship: large brains may permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing for reduced mortality and increased lifespan. By contrast, the developmental costs hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains, predicting correlations with pre-adult life-history phases. Here, we test novel predictions of the hypotheses in primates applied to the neocortex and cerebellum, two major brain structures with distinct developmental trajectories. While neocortical growth is allocated primarily to pre-natal development, the cerebellum exhibits relatively substantial post-natal growth. Consistent with the DCH, neocortical expansion is related primarily to extended gestation while cerebellar expansion to extended post-natal development, particularly the juvenile period. Contrary to the CBH, adult lifespan explains relatively little variance in the whole brain or neocortex volume once pre-adult life-history phases are accounted for. Only the cerebellum shows a relationship with lifespan after accounting for developmental periods. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental phases, and imply that environmental input during post-natal maturation may be particularly crucial for the development of cerebellar function. They also suggest that relatively extended post-natal maturation times provide a developmental mechanism for the marked expansion of the cerebellum in the apes.
Milk of ruminants in ceramic baby bottles from prehistoric child graves
Julie Dunne et al.
Nature, 10 October 2019, Pages 246-248
Abstract:
The study of childhood diet, including breastfeeding and weaning, has important implications for our understanding of infant mortality and fertility in past societies. Stable isotope analyses of nitrogen from bone collagen and dentine samples of infants have provided information on the timing of weaning; however, little is known about which foods were consumed by infants in prehistory. The earliest known clay vessels that were possibly used for feeding infants appear in Neolithic Europe, and become more common throughout the Bronze and Iron Ages. However, these vessels - which include a spout through which liquid could be poured - have also been suggested to be feeding vessels for the sick or infirm. Here we report evidence for the foods that were contained in such vessels, based on analyses of the lipid ‘fingerprints’ and the compound-specific δ13C and Δ13C values of the major fatty acids of residues from three small, spouted vessels that were found in Bronze and Iron Age graves of infants in Bavaria. The results suggest that the vessels were used to feed infants with milk products derived from ruminants. This evidence of the foodstuffs that were used to either feed or wean prehistoric infants confirms the importance of milk from domesticated animals for these early communities, and provides information on the infant-feeding behaviours that were practised by prehistoric human groups.
Genetic contributions to variation in human stature in prehistoric Europe
Samantha Cox et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
The relative contributions of genetics and environment to temporal and geographic variation in human height remain largely unknown. Ancient DNA has identified changes in genetic ancestry over time, but it is not clear whether those changes in ancestry are associated with changes in height. Here, we directly test whether changes over the past 38,000 y in European height predicted using DNA from 1,071 ancient individuals are consistent with changes observed in 1,159 skeletal remains from comparable populations. We show that the observed decrease in height between the Early Upper Paleolithic and the Mesolithic is qualitatively predicted by genetics. Similarly, both skeletal and genetic height remained constant between the Mesolithic and Neolithic and increased between the Neolithic and Bronze Age. Sitting height changes much less than standing height - consistent with genetic predictions - although genetics predicts a small post-Neolithic increase that is not observed in skeletal remains. Geographic variation in stature is also qualitatively consistent with genetic predictions, particularly with respect to latitude. Finally, we hypothesize that an observed decrease in genetic heel bone mineral density in the Neolithic reflects adaptation to the decreased mobility indicated by decreased femoral bending strength. This study provides a model for interpreting phenotypic changes predicted from ancient DNA and demonstrates how they can be combined with phenotypic measurements to understand the relative contribution of genetic and developmentally plastic responses to environmental change.
The earliest evidence for mechanically delivered projectile weapons in Europe
Katsuhiro Sano et al.
Nature Ecology & Evolution, October 2019, Pages 1409-1414
Abstract:
Microscopic analysis of backed lithic pieces from the Uluzzian technocomplex (45-40 thousand yr ago) at Grotta del Cavallo (southern Italy) reveals their use as mechanically delivered projectile weapons, attributed to anatomically modern humans. Use-wear and residue analyses indicate that the lithics were hunting armatures hafted with complex adhesives, while experimental and ethnographic comparisons support their use as projectiles. The use of projectiles conferred a hunting strategy with a higher impact energy and a potential subsistence advantage over other populations and species.
Great Lakes Copper and Shared Mortuary Practices on the Atlantic Coast: Implications for Long-Distance Exchange during the Late Archaic
Matthew Sanger et al.
American Antiquity, October 2019, Pages 591-609
Abstract:
Analysis of human remains and a copper band found in the center of a Late Archaic (ca. 5000-3000 cal BP) shell ring demonstrate an exchange network between the Great Lakes and the coastal southeast United States. Similarities in mortuary practices suggest that the movement of objects between these two regions was more direct and unmediated than archaeologists previously assumed based on “down-the-line” models of exchange. These findings challenge prevalent notions that view preagricultural Native American communities as relatively isolated from one another and suggest instead that wide social networks spanned much of North America thousands of years before the advent of domestication.
Kinship-based social inequality in Bronze Age Europe
Alissa Mittnik et al.
Science, forthcoming
Abstract:
Revealing and understanding the mechanisms behind social inequality in prehistoric societies is a major challenge. By combining genome wide data, isotopic evidence as well as anthropological and archaeological data, we go beyond the dominating supra-regional approaches in archaeogenetics to shed light on the complexity of social status, inheritance rules and mobility during the Bronze Age. We apply a deep micro-regional approach and analyze genome wide data of 104 human individuals deriving from farmstead-related cemeteries from the Late Neolithic to the Middle Bronze Age in southern Germany. Our results reveal that individual households lasting several generations consisted of a high-status core family and unrelated low-status individuals, a social organization accompanied by patrilocality and female exogamy, and the stability of this system over 700 years.
Ancient Maya wetland fields revealed under tropical forest canopy from laser scanning and multiproxy evidence
Timothy Beach et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
We report on a large area of ancient Maya wetland field systems in Belize, Central America, based on airborne lidar survey coupled with multiple proxies and radiocarbon dates that reveal ancient field uses and chronology. The lidar survey indicated four main areas of wetland complexes, including the Birds of Paradise wetland field complex that is five times larger than earlier remote and ground survey had indicated, and revealed a previously unknown wetland field complex that is even larger. The field systems date mainly to the Maya Late and Terminal Classic (∼1,400-1,000 y ago), but with evidence from as early as the Late Preclassic (∼1,800 y ago) and as late as the Early Postclassic (∼900 y ago). Previous study showed that these were polycultural systems that grew typical ancient Maya crops including maize, arrowroot, squash, avocado, and other fruits and harvested fauna. The wetland fields were active at a time of population expansion, landscape alteration, and droughts and could have been adaptations to all of these major shifts in Maya civilization. These wetland-farming systems add to the evidence for early and extensive human impacts on the global tropics. Broader evidence suggests a wide distribution of wetland agroecosystems across the Maya Lowlands and Americas, and we hypothesize the increase of atmospheric carbon dioxide and methane from burning, preparing, and maintaining these field systems contributed to the Early Anthropocene.