Macho G.A.,Research Laboratory for Archaeology
Human Evolution | Year: 2015
Hominin brain size continues to be the focus of intense research. However, relatively little attention has thus far been given to the causes and mechanisms that led to the initial, albeit moderate, brain size increase among australopiths and/or the reasons why this increase was followed by a relatively long period of stasis until the emergence of Homo. To address this issue I take a comparative phylogenetic approach that investigates the scaling relationship between brain size and body mass in catarrhines. Unlike traditional studies, body mass of the opposite sex is factored into the allometric relationships. The results obtained throw new light on the possible causes underlying early hominin encephalisation. Phylogenetically controlled analyses reveal a complex pattern, whereby brain size in both sexes is correlated with body mass of the larger sex, i.e. males. Hence, in cases where male body size has been the target of selection, either through sexual or natural selection, females have larger endocranial volumes than expected on the basis of their body masses alone, irrespective of family, dietary ecology or social organisation; this bias is seen for average values also. The scaling coefficients suggest a genetic, i.e. pleiotropic, link between both structures. Against this backdrop it is unsurprising that the sexually dimorphic early australopiths were also slightly encephalised: These hominins probably had brain sizes expected for their body size and sexual dimorphism. The higher energy requirements of their larger brains, together with environmental changes during the late Miocene/early Pliocene, most likely underlie the changes in dietary ecology observed in the hominin fossil record. By switching to a ubiquitous, energy-rich C4 (mainly) plant food niche hominins were able to sustain their larger brains without compromising other aspects of their biology, e.g. time for socialising. This made further brain size increases possible later in their evolution, i.e. with the emergence of Homo.
O'Meara D.B.,University College Cork |
O'Meara D.B.,Waterford Institute of Technology |
Edwards C.J.,Trinity College Dublin |
Edwards C.J.,Research Laboratory for Archaeology |
And 11 more authors.
Biological Journal of the Linnean Society | Year: 2012
The present study examined the contemporary genetic composition of the Eurasian badger, Meles meles, in Ireland, Britain and Western Europe, using six nuclear microsatellite loci and a 215-bp fragment of the mitochondrial DNA control region. Significant population structure was evident within Europe (global multilocus microsatellite FST=0.205, P<0.001; global mitochondrial control region ΦST=0.399, P<0.001). Microsatellite-based cluster analyses detected one population in Ireland, whereas badgers from Britain could be subdivided into several populations. Excluding the island populations of Ireland and Britain, badgers from Western Europe showed further structuring, with evidence of discrete Scandinavian, Central European, and Spanish populations. Mitochondrial DNA cluster analysis grouped the Irish population with Scandinavia and Spain, whereas the majority of British haplotypes grouped with those from Central Europe. The findings of the present study suggest that British and Irish badger populations colonized from different refugial areas, or that there were different waves of colonization from the source population. There are indications for the presence of an Atlantic fringe element, which has been seen in other Irish species. We discuss the results in light of the controversy about natural versus human-mediated introductions. © 2012 The Linnean Society of London.
Beaumont J.,University of Bradford |
Geber J.,Queen's University of Belfast |
Powers N.,Museum of London Archaeology |
Wilson A.,University of Bradford |
And 2 more authors.
American Journal of Physical Anthropology | Year: 2013
Historical evidence documents mass migration from Ireland to London during the period of the Great Irish Famine of 1845-52. The rural Irish were reliant on a restricted diet based on potatoes but maize, a C4 plant, was imported from the United States of America in 1846-47 to mitigate against Famine. In London, Irish migrants joined a population with a more varied diet. To investigate and characterize their diet, carbon and nitrogen isotope ratios were obtained from bone collagen of 119 and hair keratin of six individuals from Lukin Street cemetery, Tower Hamlets (1843-54), and bone collagen of 20 individuals from the cemetery at Kilkenny Union Workhouse in Ireland (1847-51). A comparison of the results with other contemporaneous English populations suggests that Londoners may have elevated δ15N compared with their contemporaries in other cities. In comparison, the Irish group have lower δ15N. Hair analysis combined with bone collagen allows the reconstruction of perimortem dietary changes. Three children aged 5-15 years from Kilkenny have bone collagen δ13C values that indicate consumption of maize (C4). As maize was only imported into Ireland in quantity from late 1846 and 1847, these results demonstrate relatively rapid bone collagen turnover in children and highlight the importance of age-related bone turnover rates, and the impact the age of the individual can have on studies of short-term dietary change or recent migration. Stable light isotope data in this study are consistent with the epigraphic and documentary evidence for the presence of migrants within the London cemetery. Am J Phys Anthropol, 2013. © 2012 Wiley Periodicals, Inc.
News Article | October 28, 2015
A new study of chickens overturns the popular assumption that evolution is only visible over long time scales. By studying individual chickens that were part of a long-term pedigree, the scientists led by Professor Greger Larson at Oxford University's Research Laboratory for Archaeology, found two mutations that had occurred in the mitochondrial genomes of the birds in only 50 years. For a long time scientists have believed that the rate of change in the mitochondrial genome was never faster than about 2% per million years. The identification of these mutations shows that the rate of evolution in this pedigree is in fact 15 times faster. In addition, by determining the genetic sequences along the pedigree, the team also discovered a single instance of mitochondrial DNA being passed down from a father. This is a surprising discovery, showing that so-called 'paternal leakage' is not as rare as previously believed.
Lee-Thorp J.A.,Research Laboratory for Archaeology |
Sponheimer M.,University of Colorado at Boulder |
Passey B.H.,Johns Hopkins University |
De Ruiter D.J.,Texas A&M University |
Cerling T.E.,University of Utah
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010
Accumulating isotopic evidence from fossil hominin tooth enamel has provided unexpected insights into early hominin dietary ecology. Among the South African australopiths, these data demonstrate significant contributions to the diet of carbon originally fixed by C4 photosynthesis, consisting of C4 tropical/savannah grasses and certain sedges, and/or animals eating C4 foods. Moreover, high-resolution analysis of tooth enamel reveals strong intra-tooth variability in many cases, suggesting seasonal-scale dietary shifts. This pattern is quite unlike that seen in any great apes, even 'savannah' chimpanzees. The overall proportions of C4 input persisted for well over a million years, even while environments shifted from relatively closed (ca 3 Ma) to open conditions after ca 1.8 Ma. Data from East Africa suggest a more extreme scenario, where results for Paranthropus boisei indicate a diet dominated (approx. 80%) by C4 plants, in spite of indications from their powerful 'nutcracker' morphology for diets of hard objects. We argue that such evidence for engagement with C4 food resources may mark a fundamental transition in the evolution of hominin lineages, and that the pattern had antecedents prior to the emergence of Australopithecus africanus. Since new isotopic evidence from Aramis suggests that it was not present in Ardipithecus ramidus at 4.4 Ma, we suggest that the origins lie in the period between 3 and 4 Myr ago. © 2010 The Royal Society.
Macho G.A.,Research Laboratory for Archaeology |
Lee-Thorp J.A.,Research Laboratory for Archaeology
PLoS ONE | Year: 2014
Factors influencing the hominoid life histories are poorly understood, and little is known about how ecological conditions modulate the pace of their development. Yet our limited understanding of these interactions underpins life history interpretations in extinct hominins. Here we determined the synchronisation of dental mineralization/eruption with brain size in a 20 th century museum collection of sympatric Gorilla gorilla and Pan troglodytes from Central Cameroon. Using δ13C and δ15N of individuals' hair, we assessed whether and how differences in diet and habitat use may have impacted on ape development. The results show that, overall, gorilla hair δ13C and δ15N values are more variable than those of chimpanzees, and that gorillas are consistently lower in δ13C and δ15N compared to chimpanzees. Within a restricted, isotopically-constrained area, gorilla brain development appears delayed relative to dental mineralization/eruption [or dental development is accelerated relative to brains]: only about 87.8% of adult brain size is attained by the time first permanent molars come into occlusion, whereas it is 92.3% in chimpanzees. Even when M1s are already in full functional occlusion, gorilla brains lag behind those of chimpanzee (91% versus 96.4%), relative to tooth development. Both bootstrap analyses and stable isotope results confirm that these results are unlikely due to sampling error. Rather, δ15N values imply that gorillas are not fully weaned (physiologically mature) until well after M1 are in full functional occlusion. In chimpanzees the transition from infant to adult feeding appears (a) more gradual and (b) earlier relative to somatic development. Taken together, the findings are consistent with life history theory that predicts delayed development when non-density dependent mortality is low, i.e. in closed habitats, and with the "risk aversion" hypothesis for frugivorous species as a means to avert starvation. Furthermore, the results highlight the complexity and plasticity of hominoid/hominin development. © 2014 Macho, Lee-Thorp.
Pellegrini M.,University of Bradford |
Lee-Thorp J.A.,University of Bradford |
Lee-Thorp J.A.,Research Laboratory for Archaeology |
Donahue R.E.,University of Bradford
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011
Comparisons between the oxygen isotope ratios in the carbonate and phosphate fractions of bioapatite have been proposed and applied as an internal check for diagenesis because oxygen in the two compartments is believed to be incorporated simultaneously from the same body water. It has become clear, however, that the relationship is quite variable and for some time this variability was thought to be induced by a "species" effect, although it has never been clear why that should be the case. We studied sequential samples in enamel crowns of eight equid and cervid teeth from five different Upper Palaeolithic sites in peninsular Italy, encompassing an area with different geological units. Results suggest that δ18Oc values are slightly attenuated compared to the δ18Op values in their seasonal profiles. The observation is unexpected if both bioapatite mineral fractions precipitate simultaneously from body water. One explanation could be diagenetic effects on the carbonate fraction. The same pattern, however, has been observed in data comparing incremental δ18Oc and δ18Op in modern mammal enamel crowns. If confirmed, attenuation of intra-tooth δ18Oc sequences compared to δ18Op variability would imply that seasonal climate inferences from the two proxies are not completely equivalent. Our results may also go some way in explaining the extent of variability amongst different sets of data in the δ18Op/δ18Oc relationship and suggest that the classical approach in the bioapatite community of using a constant offset between δ18Op and δ18Oc values needs to be approached with caution. © 2011 Elsevier B.V.