Studying the causes of biological diversification and the main environmental drivers involved is useful not only for the progress of fundamental science but also to inform conservation practices. Unraveling the origin and maintenance of the comparatively high Neotropical biodiversity is important to understand the global latitudinal biodiversity gradients (LBGs), which is one of the more general and conspicuous biogeographical patterns on Earth. This chapter reviews the historical development of the study of Neotropical diversification, in order to highlight the influence of methodological progress and to identify the conceptual developments that have appeared through history. Four main steps are recognized and analyzed, namely the discovery of the LBGs by pioneer naturalists, the first biogeographic studies, the inception of paleoecology and the recent revolution of molecular phylogeography. This historical account ends with an update of the current state of the study of Neotropical diversification and the main conceptual handicaps that are believed to slow progress towards a general theory on this topic. Among these constraints, emphasis is placed on (i) the shifting from one paradigm to another, (ii) the extrapolation from particular case studies to the whole Neotropics, (iii) the selection of biased evidence to support either one or another hypothesis, (iv) the assumption that Pleistocene diversification equals to refuge diversification, and (v) the straightforward inference of diversification drivers from diversification timing. The main corollary is that the attainment of a general theory on Neotropical diversification is being delayed by conceptual, rather than methodological causes. Some solutions are proposed based on the Chamberlin’s multiple-working-hypotheses scheme and a conceptual research framework to address the problem from this perspective is suggested.
After decades of human-deterministic explanations for the collapse of the ancient Rapanui civilization that inhabited Easter Island (Rapa Nui) before European contact (1722 CE), paleoecological studies developed during the last decade have provided sound evidence for climate changes and their potential socio-ecological impact. Especially significant is the occurrence of a century-scale (1570-1720 CE) drought occurred during the Little Ice Age. Freshwater is a critical resource at Easter Island that heavily depends on rain, which maintains the three only permanent surficial freshwater sources of the island: two lakes (Kao and Raraku) and a marsh (Aroi). In these conditions, the LIA drought could have significantly affected human life; however, the Rapanui civilization remained healthy showing a remarkable resilience. There are two main hypotheses on how the ancient Rapanui civilization could have obtained freshwater to guarantee its continuity. The intra-island migration hypothesis proposes that Lake Raraku, the cultural center of this civilization, dried out and the Rapanui were forced to migrate to Lake Kao, which was likely the only surficial freshwater source during the LIA drought. This shift was accompanied a profound cultural reorganization. The coastal groundwater hypothesis dismisses the use of lakes and other surficial freshwater sources to maintain the water-stressed Rapanui population and contends that the only routine freshwater sources during the LIA drought were the abundant and widespread coastal seeps fed by fresh/brackish groundwater. The pros and cons of these two hypotheses are discussed on the basis of the available archaeological and paleoecological evidence and it is concluded that, in the present state of knowledge, none of them can be rejected. Therefore, these two proposals could be complementary, rather than excluding.
In the coming years, the Anthropocene Working Group (AWG) will submit its proposal on the ‘Anthropocene’ as a new geological epoch to the International Commission on Stratigraphy (ICS) for approval. If approved, the proposal will be send to the International Union of Geological Sciences (IUGS) for ratification. If the proposal is approved and ratified, the ‘Anthropocene’ will be formalised and the Holocene Series/Epoch will be officially terminated. Currently, the ‘Anthropocene’ is a broadly used term and concept in a wide range of scientific and non-scientific situations and, for many, the official acceptance of this term is only a matter of time. However, the AWG proposal, in its present state, seems to not fully meet the ICS requirements for a new geological epoch. This paper asks what could happen if the current ‘Anthropocene’ proposal is not formalised by the ICS/IUGS. The possible stratigraphic alternatives are evaluated on the basis of the more recent literature and the personal opinions of distinguished AWG and ICS members. The eventual impact on environmental sciences and on non-scientific sectors, where the ‘Anthropocene’ seems already firmly rooted and de facto accepted as a new geological epoch, are also discussed.
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