The ‘mosaic habitat’ concept in human evolution: past and present

The habitats preferred by hominins and other species are an important theme in palaeoanthropology, and the ‘mosaic habitat’ (also referred to as habitat heterogeneity) has been a central concept in this regard for the last four decades. Here we explore the development of this concept – loosely defined as a range of different habitat types, such as woodlands, riverine forest and savannah within a limited spatial area– in studies of human evolution in the last sixty years or so. We outline the key developments that took place before and around the time when the term ‘mosaic’ came to wider palaeoanthropological attention. To achieve this we used an analysis of the published literature, a study of illustrations of hominin evolution from 1925 onwards and an email survey of senior researchers in palaeoanthropology and related fields. We found that the term mosaic starts to be applied in palaeoanthropological thinking during the 1970’s due to the work of a number of researchers, including Karl Butzer and Glynn Isaac , with the earliest usage we have found of ‘mosaic’ in specific reference to hominin habitats being by Adriaan Kortlandt (1972). While we observe a steady increase in the numbers of publications reporting mosaic palaeohabitats, in keeping with the growing interest and specialisation in various methods of palaeoenvironmental reconstruction, we also note that there is a lack of critical studies that define this habitat, or examine the temporal and spatial scales associated with it. The general consensus within the field is that the concept now requires more detailed definition and study to evaluate its role in human evolution

Influences of Temperature and Secondary Environmental Parameters on Planktonic Foraminiferal Mg/Ca: A New Core-Top Calibration

The accuracy of the Mg/Ca paleothermometer is contested over the influences of secondary environmental parameters such as salinity and pH. Recent calibrations based on compiled sediment trap and laboratory culture data suggest moderate influences from salinity and pH. Core tops are the best analogues to downcore samples used for paleoceanographic reconstruction with well‐constrained environmental parameters and thus can be used to validate sediment trap and laboratory culture calibrations. Here, we calibrate new core‐top Mg/Ca data in Globigerinoides ruber (white) and Trilobatus sacculifer (without final sac‐like chamber) with sea surface temperature, salinity, and pH. Part of these coretops were previously used to argue for a large salinity effect on G. ruber (w) Mg/Ca (Arbuszewski et al., 2010, http://10.0.3.248/j.epsl.2010.10.035). Our new G. ruber (w) Mg/Ca data are on average 12% lower than the previous results. Our calibrations yield Mg/Ca‐temperature sensitivities of 8.1 ± 0.7%/°C for G. ruber (w) and 6.6 ± 0.8%/°C for T. sacculifer (w/o sac), and Mg/Ca salinity effects of 4.7 ± 2.4%/‰ for G. ruber (w) and 5.5 ± 2.3%/‰ for T. sacculifer (w/o sac). These results agree well with culture experiments but discount the large salinity effects reported in previous core‐top studies. Our data reveal insignificant pH effects on Mg/Ca in both species. Overall, our core‐top calibrations for G. ruber (w) and T. sacculifer (w/o sac) lend strong support to previous calibrations, strengthening our confidence in the use of planktonic Mg/Ca as a reliable proxy for sea surface temperature reconstructions.This research is supported by ARC Future Fellowship (FT140100993), Discovery Projects (DP140101393 and DP190100894), and NSFC (41676026) to J. Y. New data generated in this study are archived on Pangaea (https://doi.pangaea.de/ 10.1594/PANGAEA.905128)

Impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in Porites corals

Restricted zones of recent dissolution and secondary aragonite infilling were identified in a coral core collected in 1986 from a living massive Porites colony from the central Great Barrier Reef, Australia. Secondary aragonite needles, ≥20 μm long, c

Tracking the extent of the South Pacific Convergence Zone since the early 1600s

[ 1] The South Pacific Convergence Zone (SPCZ) is the largest and most persistent spur of the Intertropical Convergence Zone. At the southeastern edge of the SPCZ near 170 degrees W and 15 degrees - 20 degrees S a surface ocean salinity frontal zone exists that separates fresher Western Pacific Warm Pool water from saltier and cooler waters in the east. This salinity front is known to shift east and west with the phase of the El Nino Southern Oscillation. We have generated subannually resolved and replicated coral oxygen isotopic time series from Fiji ( 17 degrees S, 179 degrees E) and Rarotonga (21.5 degrees S, 160 degrees W) that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front, and eastern extent of the SPCZ, has shifted east-west through 10 degrees to 20 degrees of longitude three times during this interval. The most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites. Our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the SPCZ since the mid 1800s. The expansion of the SPCZ implies a gradual change in the South Pacific to more La Nina-like long-term mean conditions. This observation is consistent with the ocean thermostat mechanism for the Pacific coupled ocean-atmosphere system, whereby exogenous heating of the atmosphere would result in greater warming in the western Pacific and a greater east-west surface temperature gradient

The influence of salinity on Mg/Ca in planktic foraminifers - Evidence from cultures, core-top sediments and complementary δ 18 O

The Mg/Ca ratio in foraminiferal calcite is one of the principal proxies used for paleoceanographic temperature reconstructions, but recent core-top sediment observations suggest that salinity may exert a significant secondary control on planktic foramin

Interlaboratory comparison study of Mg/Ca and Sr/Ca measurements in planktonic foraminifera for paleoceanographic research

Thirteen laboratories from the USA and Europe participated in an intercomparison study of Mg/Ca and Sr/Ca measurements in foraminifera. The study included five planktonic species from surface sediments from different geographical regions and water depths. Each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples. Analysis of solutions of known Mg/Ca and Sr/Ca ratios showed that the intralaboratory instrumental precision is better than 0.5% for both Mg/Ca and Sr/Ca measurements, regardless whether ICP-OES or ICP-MS is used. The interlaboratory precision on the analysis of standard solutions was about 1.5% and 0.9% for Mg/Ca and Sr/Ca measurements, respectively. These are equivalent to Mg/Ca-based temperature repeatability and reproducibility on the analysis of solutions of ±0.2°C and ±0.5°C, respectively. The analysis of foraminifera suggests an interlaboratory variance of about ±8% (%RSD) for Mg/Ca measurements, which translates to reproducibility of about ±2–3°C. The relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability (about ±1–2°C) and a bias (about 1°C) due to the application of different cleaning methods by different laboratories. Improving the consistency of cleaning methods among laboratories will, therefore, likely lead to better reproducibility. Even more importantly, the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility