Hunting and nuclear families: some lessons from the Hadza about men's work

Journal ArticleHadza hunter-gatherers display economic and social features usually assumed to indicate the dependence of wives and children on provisioning husbands and fathers. The wives and children of better Hadza hunters have been found to be better-nourished, consistent with the assumption that men hunt to provision their families. Yet, as is common among foragers, the Hadza share meat widely. Analyses of meat-sharing data confirm that little of the meat from large prey went to the hunter's own household. These analyses also show that neither a man's hunting success nor the time he spent hunting made any difference in how much meat his family got from the kills of others. Here we address questions posed by this set of observations. What explains the better nutrition of the children of better hunters if they did not get differential rations of meat? If better hunters got no more meat for their effort and poorer hunters were not punished with less, what incentive could account for the continuing disproportionate contribution that some men made to the group's nutrition? If women were not dependent on their husband's hunting success for meat, an obvious incentive for women to marry hunters disappears. We briefly consider the implications of these patterns for the evolution of marriage and nuclear families

On the design and feasibility of refractory metal-base Superalloys

Over the last 60 years, the evolution of nickel-base superalloys has enabled successive generations of gas turbine engines to operate at progressively higher temperatures. However, despite continued research activity, capability enhancement has become incremental and it seems unlikely that nickel-base superalloys will be able to support the requirements of future engine designs. Therefore, to enable a step change in operating temperatures, it is necessary to identify and develop new alloy systems, which, in addition to higher temperature capability, also have the correct balance of mechanical and environmental properties. Here, we outline an alloy design philosophy and report on the initial characterisation of one of the potential alloy systems. High temperature properties are dominated by the melting temperature and crystal structure of the principal element. Thus, only 11 elements offer capability above that of nickel-base alloys. However, if terrestrial abundance and cost are also considered, then only the bcc refractory metals remain as viable options. Intrinsic environmental resistance above 1000˚C can be afforded only by the formation of protective silica or alumina scales, requiring the incorporation of at least one of these elements in reasonable concentrations. In addition the required balance of mechanical properties is only likely to be achieved by the production of a microstructure containing a fine dispersion of small intermetallic precipitates, which have a coherent superlattice structure of solid solution matrix. The simplest materials identified by this approach are ternary refractory metal-base alloys, e.g. Ta‑Al‑Co. However, the phase equilibria of these systems, particularly in the refractory rich corners, are poorly defined. To address this issue and explore the potential of these materials, a series of alloys in the Ta-rich corner of the Ta‑Al‑Co system have been created and characterised following 500 hour heat treatments at temperatures between 1000 and 1300 ̊C. As part of this work the first conclusive evidence of a large-unit-celled Ta2AlCo phase was obtained, which may give potential for refractory metal-base superalloys

Design, characterisation and properties of Mo-Ti-Fe alloys reinforced by ordered intermetallic precipitates

Reinforcement of solid solution matrices with ordered intermetallic precipitates is known to be an effective strategy for obtaining high strength, damage tolerant alloys and has been central to the success of nickel based superalloys. This strategy has also been exploited in a number of bcc-based systems, for example in maraging steels where ferrite is strengthened by L21 (Heusler) and/or B2 structured intermetallic precipitates. However, only limited studies have explored the possibility of extending this approach to bcc alloys based on refractory metals and titanium. Recent research has shown that titanium-iron alloys comprising eutectic A2 Ti and B2 TiFe phases may be produced with strengths of over 2.5 GPa, alongside elongations to failures of ~15%. These impressive properties are thought to be a result of a fine microstructural length scale and a high lattice misfit between the phases. Here, we report on the phase equilibria in the Mo-Ti-Fe ternary system. In this system, an extensive two-phase field was identified between B2 TiFe intermetallic phase and the A2 (Ti, Mo) solid solution, that extended to Mo rich compositions. Knowledge of how this phase equilibrium varies with temperature enabled the design of alloys that could be homogenised in the single-phase solid solution and subsequently reinforced by solid state precipitates following a lower temperature heat treatment. The microstructure obtained was finer than has been produced through an invariant reaction and an initial assessment of their mechanical properties revealed substantial strength. The prospects for modifying these alloys to enable their use at higher temperatures will be discussed. This work was supported through the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1 and EP/H500375/1, as well as the DARE project under EP/L025213/1

When fecundity does not equal fitness: evidence of an offspring quantity versus quality trade-off in pre-industrial humans

Maternal fitness should be maximized by the optimal division of reproductive investment between offspring number and offspring quality. While evidence for this is abundant in many taxa, there have been fewer tests in mammals, and in particular, humans. We used a dataset of humans spanning three generations from pre-industrial Finland to test how increases in maternal fecundity affect offspring quality and maternal fitness in contrasting socio-economic conditions. For ‘resource-poor’ landless families, but not ‘resource-rich’ landowning families, maternal fitness returns diminished with increased maternal fecundity. This was because the average offspring contribution to maternal fitness declined with increased maternal fecundity for landless but not landowning families. This decline was due to reduced offspring recruitment with increased maternal fecundity. However, in landowning families, recruited offspring fecundity increased with increased maternal fecundity. This suggests that despite decreased offspring recruitment, maternal fitness is not reduced in favourable socio-economic conditions due to an increase in subsequent offspring fecundity. These results provide evidence consistent with an offspring quantity–quality trade-off in the lifetime reproduction of humans from poor socio-economic conditions. The results also highlight the importance of measuring offspring quality across their whole lifespan to estimate reliably the fitness consequences of increased maternal fecundity

Species compositions of elasmobranchs caught by three different commercial fishing methods off southwestern Australia, and biological data for four abundant bycatch species

Commercial catches taken in southwestern Australian waters by trawl fisheries targeting prawns and scallops and from gillnet and long-line fisheries targeting sharks were sampled at different times of the year between 2002 and 2008. This sampling yielded 33 elasmobranch species representing 17 families. Multivariate statistics elucidated the ways in which the species compositions of elasmobranchs differed among fishing methods and provided benchmark data for detecting changes in the elasmobranch fauna in the future. Virtually all elasmobranchs caught by trawling, which consisted predominantly of rays, were discarded as bycatch, as were approximately a quarter of the elasmobranchs caught by both gillnetting and longlining. The maximum lengths and the lengths at maturity of four abundant bycatch species, Heterodontus portusjacksoni, Aptychotrema vincentiana, Squatina australis, and Myliobatis australis, were greater for females than males. The L50 determined for the males of these species at maturity by using full clasper calcification as the criterion of maturity did not differ significantly from the corresponding L50 derived by using gonadal data as the criterion for maturity. The proportions of the individuals of these species with lengths less than those at which 50% reach maturity were far greater in trawl samples than in gillnet and long-line samples. This result was due to differences in gear selectivity and to trawling being undertaken in shallow inshore waters that act as nursery areas for these species. Sound quantitative data on the species compositions of elasmobranchs caught by commercial fisheries and the biological characteristics of the main elasmobranch bycatch species are crucial for developing strategies for conserving these important species and thus the marine ecosystems of which they are part

An assessment of the lattice strain in the CrMnFeCoNi high-entropy alloy

The formation of single phase solid solutions from combinations of multiple principal elements, with differing atomic radii, has led to the suggestion that the lattices of high-entropy alloys (HEAs) must be severely distorted. To assess this hypothesis, total scattering measurements using neutron radiation have been performed on the CrMnFeCoNi alloy and compared with similar data from five compositionally simpler materials within the same system. The Bragg diffraction patterns from all of the studied materials were similar, consistent with a face-centered cubic structure, and none showed the pronounced dampening that would be expected from a highly distorted lattice. A more detailed evaluation of the local lattice strain was made by considering the first six coordination shells in the pair distribution functions (PDF), obtained from the total scattering data. Across this range, the HEA exhibited the broadest PDF peaks but these widths were not disproportionately larger than those of the simpler alloys. In addition, of all the materials considered, the HEA was at the highest homologous temperature, and hence the thermal vibrations of the atoms would be greatest. Consequently, the level of local lattice strain required to rationalise a given PDF peak width would be reduced. As a result, the data presented in this study do not indicate that the local lattice strain in the equiatomic CrMnFeCoNi HEA is anomalously large.The authors would like to thank the EPSRC/Rolls-Royce Strategic Partnership for funding (EP/M005607/1 and EP/H022309).This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.actamat.2016.09.03

The 3s Proton Occupancy in 206-Pb

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Test of the DWBA Description of Transfer Reactions at Intermediate Energies by Measuring a Complete Set of Single Nucleon Transfer and Elastic Scattering Data

This research was sponsored by the National Science Foundation Grant NSF PHy 87-1440