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Competition among species and entire clades can impact species diversification and extinction, which can shape macroevolutionary patterns. The fossil record shows successive biotic turnovers such that a dominant group is replaced by another. One striking example involves the decline of gymnosperms and the rapid diversification and ecological dominance of angiosperms in the Cretaceous. It is generally believed that angiosperms outcompeted gymnosperms, but the macroevolutionary processes and alternative drivers explaining this pattern remain elusive. Using extant time trees and vetted fossil occurrences for conifers, we tested the hypotheses that clade competition or climate change led to the decline of conifers at the expense of angiosperms. Here, we find that both fossil and molecular data show high congruence in revealing 1) low diversification rates, punctuated by speciation pulses, during warming events throughout the Phanerozoic and 2) that conifer extinction increased significantly in the Mid- Cretaceous (100 to 110 Ma) and remained high ever since. Their extinction rates are best explained by the rise of angiosperms, rejecting alternative models based on either climate change or time alone. Our results support the hypothesis of an active clade replacement, implying that direct competition with angiosperms increased the extinction of conifers by pushing their remaining species diversity and dominance out of the warm tropics. This study illustrates how entire branches on the Tree of Life may actively compete for ecological dominance under changing climates.

Rice agriculture is the foundation of Asian civilizations south of the Yangtze River. Although rice history is well documented for its lower Yangtze homeland area, the early southward expansion of paddy rice farming is poorly known. Our study investigates this process using a compilation of paleoenvironmental proxies from coastal sediment cores fromsoutheast China to Thailand and Island Southeast Asia.We propose that a shortage of land suitable for paddy fields, caused by marine transgression, constrained rice agriculture during the mid-Holocene. Rapid expansion of coastal plains, particularly in deltaic basins, over the past three millennia has coincided with increases in land suitable for rice cultivation. Our study also helps explain the past population movements of rice farmers.

Understanding heterogeneity in species richness between closely related clades is a key research question in ecology and evolutionary biology. Multiple hypotheses have been proposed to interpret such diversity contrasts across the tree of life, with most studies focusing on speciation rates to explain clades’ evolutionary radiations, while often neglecting extinction rates. Here we study a notorious biological model as exemplified by the sister relationships between mackerel sharks (Lamniformes, 15 extant species) and ground sharks (Carcharhiniformes, ∼290 extant species). Using a comprehensive fossil dataset, we found that the diversity dynamics of lamniforms waxed and waned following repeated cycles of radiation phases and declining phases. Radiation phases peaked up to 3 times the current diversity in the early Late Cretaceous. In the last 20 million years, the group declined to its present-day diversity. Along with a higher extinction risk for young species, we further show that this declining pattern is likely attributed to a combination of abiotic and biotic factors, with a cooling-driven extinction (negative correlation between temperature and extinction) and clade competition with some ground sharks. Competition from multiple clades successively drove the demise and replacement of mackerel sharks due to a failure to originate facing the rise of ground sharks, particularly since the Eocene. These effects came from ecologically similar carcharhiniform species inhibiting diversification of mediumand large-sized lamniforms. These results imply that the interplay between abiotic and biotic drivers had a substantial role in extinction and speciation, respectively, which determines the sequential rise and decline of marine apex predators.

Trace elements are actively cycled in seawater, are essential components for marine life, and are transported to the seafloor where they can become enriched in marine sediments. Trace element enrichment in marine sediments depends on local hydrography, redox conditions, and biological activity. Most redox-sensitive trace elements partake in biological cycling in seawater and sedimentary pore waters, and their distribution in the rock record can help to constrain the dynamics and changes in environmental conditions on geologic timescales. Carbonate minerals including calcite, aragonite, and dolomite readily adsorb and/or incorporate trace elements during precipitation. Although experimental laboratory studies concerning incorporation of trace elements into carbonate minerals have not always yielded unambiguous results, they have generally confirmed a strong tendency of carbonate minerals to accumulate and retain certain trace elements. Because natural carbonate minerals can archive trace elements, they have attracted attention as sources of information on biogeochemical processes. Nonetheless, drawbacks of using trace element contents of marine carbonates as paleoproxies exist due to mineral alteration during early diagenesis, subsequent burial diagenesis, and meteoric diagenesis. These processes can affect trace element contents in marine carbonates to different degrees, possibly leading to alteration or even a complete loss of their original trace element composition. This review summarizes current knowledge on the behavior of trace elements in seawater and interstitial pore water by integrating trace element cycling in the water column, their transport to the seafloor, and their subsequent incorporation into carbonate minerals. This work provides a comprehensive overview for the carbonate sedimentologist, detailing the water column and early diagenetic processes that affect trace element patterns of unaltered or poorly altered carbonate rocks used as archives of paleoenvironmental change.

Addressing and anticipating future South Asian monsoon changes under continuing global warming is of critical importance for the food security and socioeconomic well-being of one-quarter of the world’s population. However, climate model projections show discrepancies in future monsoon variability in South Asian monsoon domains, largely due to our still limited understanding of the monsoon response to warm climate change scenarios. Particularly, climate models are largely based on the assumption that higher solar insolation causes higher rainfall during similar warm climatic regimes, but this has not been verified by proxy data for different interglacial periods. Here, we compare Indian summer monsoon (ISM) variability during the Last Interglacial and Holocene using a sedimentary leaf wax δD and δ13C record from the northern Bay of Bengal, representing the Ganges–Brahmaputra–Meghna (G-B-M) river catchment. In combination with a seawater salinity record, our results show that ISM intensity broadly follows summer insolation on orbital scales, but ISM intensity during the Last Interglacial was lower than during the Holocene despite higher summer insolation and greenhouse gas concentrations. We argue that sustained warmer sea surface temperature in the equatorial and tropical Indian Ocean during the Last Interglacial increased convective rainfall above the ocean but dampened ISM intensity on land. Our study demonstrates that besides solar insolation, internal climatic feedbacks also play an important role for South Asian monsoon variability during warm climate states. This work can help to improve future climate model projections and highlights the importance of understanding controls of monsoonal rainfall under interglacial boundary conditions.

The Niutitang Formation in the South China Block might be a source of hydrocarbon as it contains an enormous quantity of organic matter. Black rock of the Early Cambrian Niutitang Formation is widely distributed in the Yangtze region, but detailed geochemical understanding of it is still emerging. This research discusses the detailed geochemical characteristics of the Niutitang Formation to reconstruct the paleoenvironmental conditions, employing total organic carbon (TOC) content, major, trace, and rare earth element data. For this purpose, black rock specimens of the Niutitang Formation from two outcrop sections were utilized for geochemical characterization, and the results compared with another eight sections from the South China Block. The average total organic carbon in these sediments is significantly higher (5.80 wt.%). In the platform region, lower quantities of TOC indicate a poor potential to produce hydrocarbons. At the same time, significantly higher TOC is observed in the deep shelf and slope sediments, indicating a significant potential to produce hydrocarbons. The average Ce, Eu and Y anomalies from both Longbizui and Sancha sections studied are 0.74, 0.86, 1.77, 1.07, and 1.19, 1.30, respectively. The chemical index of alteration (CAI) throughout the Yangtze block is higher (averaging 71.32) than that of Post Archean Australian Shale (PAAS 69), indicating a moderately weathered source of the Niutitang Formation relative to PAAS. As the sediments are moderately weathered, this suggests these rocks might have been derived from felsic rocks, mainly granite-granodiorite. The normalization of REEs in the black rocks reveals a reduction of light REEs with increase in heavy REEs enrichment. Similarly, a positive Eu anomaly, negative Ce anomaly, and a moderate Y/Ho (34.61) are clues to a hybrid depositional mechanism associated with hydrothermal action and terrigenous input. These anomalies are also evidence of upwelling in the paleo-ocean and mixing of organic matter, which created anoxic bottom water during the deposition of the Niutitang Formation in the basin and upper oxic water conditions before deposition. The main controlling factors for the distribution of rare earth elements in these black rocks of the Niutitang Formation are pH, terrigenous input, source rock composition, tectonism, an upwelling mechanism, and hydrothermal activity.

Studies of climate variation commonly rely on chemical and isotopic changes recorded in sequentially produced growth layers, such as in corals, shells, and tree rings, as well as in accretionary deposits—ice and sediment cores, and speleothems. Oxygen isotopic compositions (δ 18 O) of tooth enamel are a direct method of reconstructing environmental variation experienced by an individual animal. Here, we utilize long-forming orangutan dentitions ( Pongo spp.) to probe recent and ancient rainfall trends on a weekly basis over ~3–11 years per individual. We first demonstrate the lack of any consistent isotopic enrichment effect during exclusive nursing, supporting the use of primate first molar teeth as environmental proxies. Comparisons of δ 18 O values (n=2016) in twelve molars from six modern Bornean and Sumatran orangutans reveal a high degree of overlap, with more consistent annual and bimodal rainfall patterns in the Sumatran individuals. Comparisons with fossil orangutan δ 18 O values (n=955 measurements from six molars) reveal similarities between modern and late Pleistocene fossil Sumatran individuals, but differences between modern and late Pleistocene/early Holocene Bornean orangutans. These suggest drier and more open environments with reduced monsoon intensity during this earlier period in northern Borneo, consistent with other Niah Caves studies and long-term speleothem δ 18 O records in the broader region. This approach can be extended to test hypotheses about the paleoenvironments that early humans encountered in southeast Asia. When an animal drinks water, two naturally occurring variants of oxygen – known as oxygen-18 and oxygen-16 – are incorporated into its growing teeth. The ratio of these variants in water changes with temperature, rainfall and other environmental conditions and therefore can provide a record of the climate during an animal’s life. Teeth tend to be well preserved as fossils, which makes it possible to gain insights into this climate record even millions of years after an animal’s death. Orangutans are highly endangered great apes that today live in rainforests on the islands of Borneo and Sumatra. During a period of time known as the Pleistocene (around 2.6 million years to 12,000 years ago), these apes were more widely spread across Southeast Asia. Climate records from this area in the time before human-induced climate change are somewhat limited. Therefore, fossilized orangutan teeth offer a possible way to investigate past seasonal rainfall patterns and gain insight into the kind of environments early humans would have encountered. To address this question, Smith et al. measured oxygen-18 and oxygen-16 variants in thin slices of modern-day orangutan teeth using a specialized analytical system. This established that the teeth showed seasonal patterns consistent with recent rainfall trends, and that the ratio of these oxygen variants did not appear to be impacted by milk intake in young orangutans. These findings indicated that the oxygen variants could be a useful proxy for predicting prehistoric weather patterns from orangutan teeth. Further measurements of teeth from fossilized Sumatran orangutans showed broadly similar rainfall patterns to those of teeth from modern-day orangutans. On the other hand, fossilized teeth from Borneo suggested that the environment used to be drier, with less intense wet seasons. The approach developed by Smith et al. provides an opportunity for scientists to leverage new fossil discoveries as well as existing collections to investigate past environments. This could allow future research into how climate variation may have influenced the spread of early humans through the region, as well as the evolution of orangutans and other endangered animals.

Changes in microbialite abundance during the Archean and Paleoproterozoic have been attributed to a variety of environmental and biological factors, yet past work looking at large‐scale patterns of microbialite abundance generally assumes shallow marine deposition rather than incorporating specific settings. We compiled Archean and Paleoproterozoic microbialite occurrences and depositional environment information to assess how microbialite development and preservation changed across settings. Microbially induced sedimentary structures formed a significant part of the record, but may be undercounted as they were identified mostly in units that also contained stromatolites. While broad trends in abundance resembled previous compilations, critically, we found that more microbialites formed in tidal environments than subtidal marine. The proportion of terrestrially influenced (including tidal) microbialites peaked during periods of craton development and following the Great Oxidation Event and Huronian Glaciations. These findings highlight the importance of continental landmasses and tectonic processes in defining the distribution and preservation of early life.