Search Results

A research program that takes full advantage of the quality of the archaeological record eliminates the study of most microscale processes — those that are observed within a human lifetime and that operate at the hierarchical scale of the individual — because the archaeological record is not a suitable medium to study them. Instead, an appropriate research program focuses on: (1) cultural history and (2) macroarchaeology, the search for macroscale patterns and processes in the global archaeological record. Archaeologists can also make unique contributions to the social sciences by studying macroscale processes that operate at a hierarchical level well above that of the individual, that cannot be seen within the span of a human lifetime, but that become visible only when looked from an observation window thousands of years long and thousands of kilometers wide. The archaeological record has the scope necessary to detect macroscale phenomena because it can provide samples that are large enough to cancel out the noise generated by microscale processes. In order to discover macroscale principles affecting human history, archaeologists need to build a global database of archaeological types. Such database can act as a low-pass filter that cancels out the noise generated by microscale factors.

The latitudinal diversity gradient (LDG) is a phenomenon acknowledged for over two centuries. The LDG of marine crustaceans has been studied often but without reaching consensus on its ultimate causative processes. We have undertaken a new synthesis to assess the generality of the LDG and evaluated how potential sampling and other biases, spatial scale, geographic regions, taxonomic aggregation, and differences between clades affect patterns. A meta-analysis of 186 datasets, encompassing 20 studies and 7 crustacean orders, revealed a strong effect size of the species richness-latitude correlation, supporting the existence of a “canonical” LDG. The effect size was sensitive to spatial scale, with studies conducted over shorter latitudinal ranges tending to show a weaker LDG. Correcting for sampling biases in the number of occurrences, taxonomic completeness and spatial heterogeneity did not affect the strength of the LDG, nor did the degree of taxonomic aggregation; effect sizes were similar at family and ordinal levels. However, between orders effect sizes varied strongly, with peracarid orders (Amphipoda, Cumacea, Isopoda) showing a weaker or inverse LDG compared with non-peracarid orders (Calanoida, Euphausiacea, Decapoda, Sessilia). Additional analyses based on a global dataset of >2 million occurrences of >13,000 species revealed patterns undetected by the meta-analysis, including: (1) the existence of a marked bi-modal LDG, with peaks of diversity in subtropical areas (Calanoidea, Decapoda, Sessilia) and in temperate areas (Amphipoda, Isopoda), (2) interhemispheric asymmetry, variable across groups and depths, and (3) ocean basin differences in the shape of the LDG, dependent on taxonomic clade. Both ecological and evolutionary processes play a part. The fossil record of Decapoda showed that its global canonical LDG can be explained by median and range of the age of genera, i.e., hotspots of diversity harbor both younger and older genera and contain a high proportion of genera originating during the Paleogene. In addition, the effect size was negatively related to family age, the LDG being stronger in older families of early Cenozoic and Mesozoic origin. Modes of larval development also played a significant part, taxa without planktonic larvae having weaker or inverse LDG compared with taxa with pelagic larvae. Because clades with direct development tend to show smaller bathymetric and latitudinal ranges than those with pelagic larvae, differences in diversification rates may be implied. Overall, our evidence suggested that the ultimate causes of the LDG are deeply tied to geographic differences in macro-evolutionary rates, i.e., greater rates of species origin and lower rates of extinction in the tropics than in higher latitudes combined with a strong tropical niche conservatism.

Developed countries—and many developing nations as well—face the triple threat of growing longevity, falling birthrates, and fiscal shortfalls. Drawing on the 2014 Global Findex database, which provides individual-level data on the use of financial products in more than 140 countries, we show that only about one-quarter of adults globally save for old age, with higher rates in higher income economies as well as East Asia and the Pacific. On average, men are slightly more likely than women to do this, but the gender gap is deeper in developing countries. Worldwide, saving for old age is most common for older and better educated adults, those adults with financial accounts, and people in countries having an English or German legal origin. Measures to increase trust in the financial system—such as deposit insurance—also lead to higher rates of old age saving. Finally, we find no evidence of substitution between pension system provisions and contribution rates with saving for old age.