Mangrove sediments have served as valuable archives of Late-Holocene relative sea-level (RSL) change. However, challenges such as age uncertainties due to root penetration and bioturbation, as well as elevation uncertainties from surveying, indicative meaning, and sediment compaction remain. Here, we reconstructed Late-Holocene RSL from Singapore using a multi-proxy approach combining litho- (grain size and loss on ignition), bio- (pollen), and chrono-stratigraphical (Accelerator Mass Spectrometry radiocarbon dating) techniques to produce a series of sea-level index points (SLIPs). We surveyed the SLIPs to mean tide level, quantified the indicative meaning from the contemporary mangrove environment and minimised compaction by producing mostly basal SLIPs. We developed nine SLIPs and assessed RSL change using the Error-In-Variables Integrated Gaussian Process (EIV-IGP) model. We compared the RSL reconstructions with Glacial Isostatic Adjustment (GIA) models and a database of SLIPs from the East Coast of the Malay-Thai Peninsula. Our results show that RSL gradually decreased from 0.33 +/- 0.75 m to -0.07 +/- 0.17 m between similar to 4000 cal. yrs. BP and similar to 500 cal. yrs. BP. The EIV-IGP model suggests RSL likely (66% probability) went below present-day levels between similar to 900 cal. yrs. BP and similar to 500 cal. yrs. BP, aligning with regional RSL reconstructions but differing from GIA model predictions. Potential drivers of the Late-Holocene RSL fall and subsequent rise to present include global ice-sheet expansion, regional ocean-atmosphere interactions and the subsidence of Sundaland. Future research should refine far-field RSL reconstructions to determine the extent and drivers of Late-Holocene RSL lowstands.

Tropical peatland wildfire incidence has risen in recent decades, driven by drainage for land use and intensified by severe droughts with global climate change. These disturbances have altered vegetation structure, disrupted ecosystem functioning, and increased carbon emissions, particularly in Southeast Asia. However, the long-term history and characteristics of wildfires in tropical peatlands remain largely unknown. Here, we compiled fifty-eight macro-charcoal records from peatlands across the tropics, ranging from lowland forested to montane peatlands, to assess millennia-scale changes and controlling factors of tropical peatland burning. We divided the datasets into four main sub-regions: Neotropical, Afrotropical, Indomalayan and Australasian ecoregions to explore regional variability. Tropical peatlands had high burning levels between 0 and 850 ce, followed by a relatively low and stable period until a marked increase during the 20th century. The general trend in tropical peatland burning follows changes in global temperature, and climate variables that control the length and severity of drought events have a notable influence on peat burning before 1900 ce. During the 20th century, regional differences were observed, with declining fire trends in the Neotropical and Afrotropical regions and increasing fire trends in the Indomalayan and Australasian regions. This difference is likely attributable to human activities, and such intervention is also evident in palm swamps and hardwood swamps under similar wet, weakly seasonal climates. With the increase in anthropogenic pressures on peatlands and greater climate variability, future wildfires in peatlands are likely to become more frequent and widespread across all tropical ecoregions. Conservation and sustainable land-use practices could be used to mitigate and control peatland burning and protect these carbon-rich sinks.

Ecosystems are continuously responding to both natural and anthropogenic environmental change. Lake sediments preserve local and global evidence of these ecological transitions through time. This archived information can yield crucial insights through the reconstruction of past changes over hundreds to many thousands of years. This chapter provides an overview on what lake sedimentary DNA (sedDNA) is, which biological groups can be detected with this novel paleoecological proxy, and the workflow and analytical techniques currently employed in sedDNA research. Finally, the implications of lake sedDNA studies are illustrated through five topics, illustrating how sedDNA can reconstruct lake response to environmental change.

Raised peatlands, or bogs, are recognized as exceptionally carbon-dense terrestrial ecosystems in which peat accumulates into convex shapes that rise above their boundaries. Because of this convexity, bogs are vulnerable to artificial drainage, and mapping them is important to evaluate whether and how to protect or restore their carbon stocks. Recently, we showed that hydrological constraints create a pattern in the morphology of bogs that holds under a broad range of conditions, as illustrated by eight examples of bogs from northern, through tropical and further to southern latitudes. Specifically, we found that if bog surface elevation, mean water table elevation and transmissivity are related to one another in similar ways across a bog, the relationships among these variables define a bog-specific monotonic function that generates the bog morphology from a solution to Poisson’s equation. This pattern is like a signature for raised bog morphology, and could be used to help identify the boundaries of raised bogs. In addition, the pattern can be used to infer the full morphology of bogs from limited data, which in turn enables estimation of a bog’s stock of vulnerable carbon. We discuss how these findings can be combined with field and remote sensing data to better map the extent and vulnerable carbon stocks of raised peatlands around the world.

This book addresses the interplay between geodynamics, climate, and biodiversity, focusing on the India-Asia collision, the key abiotic parameter shaping the region's topography, climate, and ecosystems. Asia, with its unparalleled geological activity and rich biodiversity, is ideal for studying interactive processes of Earth System Science. Collision shaped the Himalayan and Tibetan Plateau regions, significantly influencing atmospheric circulation, precipitation patterns, and biotic evolution. Key questions revolve around the timing and mechanisms of these processes, which remain topics of debate. Fossil records highlight evolutionary patterns, such as plant and animal dispersals during tectonic shifts like the “Africa-India Floristic Interchange.” Climatic phenomena, including monsoons and glaciations, further influenced biodiversity by shaping habitats and driving speciation. High-altitude regions, like the Hengduan Mountains, became biodiversity cradles due to habitat heterogeneity and ecological niches. Advances in tools like palaeoaltimetry proxies, molecular phylogenetics, climate and landscape modelling clarify the complex interactions between tectonics, climate, and biodiversity. Asia's geological history offers vital insights into past climate-biodiversity dynamics, aiding predictions of current ecosystem responses to climate change. This region's unparalleled geological activity and biodiversity make it a focal point for Earth System Science, highlighting the need for interdisciplinary research to address global biodiversity and environmental challenges.

Southeast Asia is a global hotspot of peatland degradation and related greenhouse gas emissions. Anthropogenic impacts, mainly associated with agricultural conversion, shift Southeast Asian peatlands from carbon sinks to significant carbon sources. Here we first describe the impacts of anthropogenic drainage on landscape-scale carbon dynamics of individual peatlands and then use an impulse‐response model of radiative forcing to quantify the climate impacts of peat-carbon losses. Whereas water-table elevation (i.e. drainage depth) determines the magnitude of CO2 emissions at the site-scale, the geometric arrangement of artificial drainage networks determines carbon losses on the landscape-scale. Among all peatland greenhouse gas fluxes, the rapid release of large quantities of CO2 with lowered water tables has the greatest impact on atmospheric radiative forcing. While peat accumulation in undisturbed peatlands produces a slowly increasing net radiative cooling, drainage, within decades, causes a shift in radiative forcing to a positive atmospheric perturbation (i.e. net warming), which can persist for centuries to millennia. The pace of this shift in radiative forcing and the magnitude and duration of the warming effect depend on the age and carbon pools of peatlands.

The Olorgesailie basin, southern Kenya Rift, is a renowned prehistoric site that preserves evidence of hominin behavior over the past ~1 million years. During this period the basin experienced environmental variability in response to orbitally controlled climate changes and tectonic forcing, which together influenced preservation of evidence for early human behavior and technological innovations. Palaeobotanical data from phytoliths extracted from outcrop paleosols show that vegetation cover varied subtly across the landscape and through time, shifting between wooded grasslands and open grasslands. Low-resolution outcrop data and a sedimentary hiatus between ~500 ka and ~320 ka hinder understanding of when important vegetation changes may have occurred and how these influenced mammalian species turnover or major transitions in hominin technology and behavior. Here we report vegetation data analyzed from a well-dated and continuous 139 m sedimentary core spanning the last ~1 million years, drilled from the southern area of the Olorgesailie catchment known as the Koora basin. Phytolith data from 270 samples show that climate largely controlled vegetation variability in the basin. These changes appear to have influenced mammalian assemblages and corresponded with changes in human behavior and technological transitions in the southern Kenya rift. Our record shows a significant shift towards more C4-short-Chloridoideae grasslands associated with increased variability in available fresh water, corresponding to the technological transition from Acheulean to Middle Stone Age around 320 ka. In addition, phytolith indices indicate increased vegetation variability 330-220 ka, corresponding to high variability in terrestrial and freshwater conditions resulting from tectonic, hydrological and ecological changes. The sediment core thus provides a unique, high-resolution opportunity to evaluate vegetation dynamics of the Olorgesailie-Koora region, providing new insights on how vegetation may have influenced our ancestors’ behavioral changes over the past ~1 million years.

The South Kenya Rift is comprised of a series of N-S-oriented grabens with sediments that preserve an approximate one-million-year environmental history that reflects the interplay of climate, tectonism and volcanism. This study attempts to disentangle the relative roles of these major controls by comparing the geochemical records preserved in three sedimentary basins. The study focuses on the Koora Basin using bulk geochemical data in a 139-m-long core. This record is then compared with geochemical data and environmental histories from a 196-m-long core at Magadi and outcrops in the Olorgesailie Basin. Four climatic phases (1000-850; 850-470; 470-400; 400-0 ka) are recognised at Koora, which can also be distinguished in the Magadi and Olorgesailie Basins. However, inter-basin contrasts also suggest that additional, non-climatic factors influenced these geochemical histories, particularly during four intervals. These include 1) the Magadi Transition (MT; -770-700 ka), 2) the Magadi Tectonic Event (MTE; -540 ka), 3) the Koora Instability Period (KIP; -325-180 ka), and 4) the Trona Precipitation Period (TPP; -105-0 ka). Prior to the MT, Zr/TiO2, La/Lu, Mo, As, V and Na/Ca in Magadi and Koora cores were similar but afterwards diverged. Major reductions in transition metals at Magadi during the MTE reflect tectonically-induced cross-rift drainage diversion. This contrasts with the Koora and Olorgesailie basins where these metals were constant from -1000 to 300 ka. The KIP represents a significant increase in volcanic inputs to the Koora Basin and increased geochemical variability. Bromine (Br), which reflects peralkaline volcanic activity and/or evaporative concentration, is elevated during the KIP at Koora but is below detection limits in the rest of the Koora core. Br in the Magadi core does not correlate with that in the Koora record, suggesting contrasting accumulation processes. The TPP represents a phase of trona precipitation at Magadi but not at Koora. This difference partly reflects increased magmatic CO2 rising along faults in the Magadi basin during a period of increasing aridity. Rare-earth element patterns indicate a major change at Magadi with many anomalies after about 325 ka to the present, caused by the development of hypersaline waters, which did not occur at Koora or Olorgesailie. The geochemical data from the three basins help to partially separate climatic controls from those related to volcanism, tectonism and local geomorphology.

The Olorgesailie basin, southern Kenya Rift, is a renowned prehistoric site that preserves evidence of hominin behavior over the past ~1 million years. During this period the basin experienced environmental variability in response to orbitally controlled climate changes and tectonic forcing, which together influenced preservation of evidence for early human behavior and technological innovations. Palaeobotanical data from phytoliths extracted from outcrop paleosols show that vegetation cover varied subtly across the landscape and through time, shifting between wooded grasslands and open grasslands. Low-resolution outcrop data and a sedimentary hiatus between ~500 ka and ~320 ka hinder understanding of when important vegetation changes may have occurred and how these influenced mammalian species turnover or major transitions in hominin technology and behavior.         Here we report vegetation data analyzed from a well-dated and continuous 139 m sedimentary core spanning the last ~1 million years, drilled from the southern area of the Olorgesailie catchment known as the Koora basin. Phytolith data from 270 samples show that climate largely controlled vegetation variability in the basin. These changes appear to have influenced mammalian assemblages and corresponded with changes in human behavior and technological transitions in the southern Kenya rift. Our record shows a significant shift towards more C4-short-Chloridoideae grasslands associated with increased variability in available fresh water, corresponding to the technological transition from Acheulean to Middle Stone Age around 320 ka. In addition, phytolith indices indicate increased vegetation variability 330-220 ka, corresponding to high variability in terrestrial and freshwater conditions resulting from tectonic, hydrological and ecological changes. The sediment core thus provides a unique, high-resolution opportunity to evaluate vegetation dynamics of the Olorgesailie-Koora region, providing new insights on how vegetation may have influenced our ancestors’ behavioral changes over the past ~1 million years.

AbstractConservation areas encompassing elevation gradients are biodiversity hotspots because they contain a wide range of habitat types in a relatively small space. Studies of biodiversity patterns along elevation gradients, mostly on small mammal or bird species, have documented a peak in diversity at mid elevations. Here, we report on a field study of medium and large mammals to examine the impact of elevation, habitat type, and gross primary productivity on community structure. Species richness was observed using a camera trap transect with 219 sites situated across different habitat types from 2329 to 4657 m above the sea level on the western slope of Mt Kenya, the second highest mountain in Africa. We found that the lowest elevation natural habitats had the highest species richness and relative abundance and that both metrics decreased steadily as elevation increased, paralleling changes in gross primary productivity, and supporting the energy richness hypothesis. We found no evidence for the mid‐domain effect on species diversity. The lowest elevation degraded Agro‐Forestry lands adjacent to the National Park had high activity of domestic animals and reduced diversity and abundance of native species. The biggest difference in community structure was between protected and unprotected areas, followed by more subtle stepwise differences between habitats at different elevations. Large carnivore species remained relatively consistent but dominant herbivore species shifted along the elevation gradient. There was some habitat specialization and turnover in species, such that the elevation gradient predicts a high diversity of species, demonstrating the high conservation return for protecting mountain ecosystems for biodiversity conservation.

Tropical peatlands are estimated to hold carbon stocks of 70 Pg C or more as partly decomposed organic matter, or peat. Peat may accumulate over thousands of years into gently mounded deposits called peat domes with a relief of several meters over distances of kilometers. The mounded shapes of tropical peat domes account for much of the carbon storage in these landscapes, but their subtle topographic relief is difficult to measure. As many of the world's tropical peatlands are remote and inaccessible, spaceborne laser altimetry data from missions such as NASA's Global Ecosystem Dynamics Investigation (GEDI) on the International Space Station (ISS) and the Advanced Topographic Laser Altimeter System (ATLAS) instrument on the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) observatory could help to describe these deposits. We evaluate retrieval of ground elevations derived from GEDI waveform data, as well as single-photon data from ATLAS, with reference to an airborne lidar dataset covering an area of over 300 km2 in the Belait District of Brunei Darussalam on the island of Borneo. Spatial filtering of GEDI L2A version 2, algorithm 1 quality data reduced mean absolute deviations from airborne-lidar-derived ground elevations from 8.35 m to 1.83 m, root-mean-squared error from 15.98 m to 1.97 m, and unbiased root-mean-squared error from 13.62 m to 0.72 m. Similarly, spatial filtering of ATLAS ATL08 version 3 ground photons from strong beams at night reduced mean absolute deviations from 1.51 m to 0.64 m, root-mean-squared error from 3.85 m to 0.77 m, and unbiased root-mean-squared error from 3.54 m to 0.44 m. We conclude that despite sparse ground retrievals, these spaceborne platforms can provide useful data for tropical peatland surface altimetry if postprocessed with a spatial filter.

The rare clariid catfish genus Encheloclarias is recorded for the first time from the peat swamp habitat in Brunei Darussalam, representing its northernmost record on the island of Borneo. Upon detailed examination, the Brunei species is keyed out to E. baculum. Using fresh material from Brunei and Sarawak (Malaysia, Borneo), the taxonomic status of E. prolatus is reviewed, and is herein synonymised with E. baculum, as first reviser's action. An updated key for all Encheloclarias species is provided, and ecological notes on the Brunei material discussed.

Raised peatlands, or bogs, are gently mounded landforms that are composed entirely of organic matter1-4 and store the most carbon per area of any terrestrial ecosystem5. The shapes of bogs are critically important because their domed morphology4,6,7 accounts for much of the carbon that bogs store and determines how they will respond to interventions8,9 to stop greenhouse gas emissions and fires after anthropogenic drainage10-13. However, a general theory to infer the morphology of bogs is still lacking4,6,7. Here we show that an equation based on the processes universal to bogs explains their morphology across biomes, from Alaska, through the tropics, to New Zealand. In contrast to earlier models of bog morphology that attempted to describe only long-term equilibrium shapes4,6,7 and were, therefore, inapplicable to most bogs14-16, our approach makes no such assumption and makes it possible to infer full shapes of bogs from a sample of elevations, such as a single elevation transect. Our findings provide a foundation for quantitative inference about the morphology, hydrology and carbon storage of bogs through Earth's history, as well as a basis for planning natural climate solutions by rewetting damaged bogs around the world.

Tropical peatlands account for a small portion of global peatland area but hold over 100 Gt of carbon (C), equivalent to approximately 13% of the C stored in the atmosphere. At this point, a comprehensive synthesis on the timing and behavior of peatland formation and peat accumulation does not exist for the tropics, where long-term accumulation rates could be higher than other regions due to the high productivity and water availability characteristic of tropical regions. In this work, we synthesize data collected from tropical peatlands around the world, to identify dominant external drivers (such as climate or tectonics) that influence patterns of peat depth and accumulation. We use radiocarbon measurements compiled in the International Soil Radiocarbon Database (ISRaD) to calculate peat and C accumulation rates of peat profiles across the tropics. Currently 44 individual studies make up this synthesis that together cover 12 countries and 62 tropical peat sites. This analysis focuses on comparisons between tropical peatlands from different continents and geographic locations and with different site characteristics. We identify three geographically distinct types of peatlands across the tropics: a) inland b) coastal c) montane that differ in terms of underlying substrate, timing of initiation, and accumulation rate. Four regions have been recognized in this analysis with differences in the range of peatland ages and depth: Africa (4000-10,600 cal yr BP) with 1-3m low elevation peatlands, the Neotropics (1400-13,000 cal yr BP) with higher variability in elevation and 1-8m peat deposits, Southeast Asia (4000-47,000 cal yr BP) with 1-18m deep peat deposits, and Hawaii (115-45,000 cal yr BP) with 1-4m peat deposits. We explore possible drivers of these differences in peatland age and accumulation across the tropics. This study complements the recent progress that has been made in mapping tropical peats, identifying their specific characteristics, assessing their potential uses, and calling attention to their potential vulnerability, restoration, and conservation.

East Africa is a global biodiversity hotspot and exhibits distinct longitudinal diversity gradients from west to east in freshwater fishes and forest mammals The assembly of this exceptional biodiversity and the drivers behind diversity gradients remain poorly understood, with diversification often studied at local scales and less attention paid to biotic exchange between Afrotropical regions. Here, we reconstruct a river system that existed for several millennia along the now semiarid Kenya Rift Valley during the humid early Holocene and show how this river system influenced postglacial dispersal of fishes and mammals due to its dual role as a dispersal corridor and barrier. Using geomorphological, geochronological, isotopic, and fossil analyses and a synthesis of radiocarbon dates, we find that the overflow of Kenyan rift lakes between 12 and 8 ka before present formed a bidirectional river system consisting of a "Northern River" connected to the Nile Basin and a "Southern River," a closed basin. The drainage divide between these rivers represented the only viable terrestrial dispersal corridor across the rift. The degree and duration of past hydrological connectivity between adjacent river basins determined spatial diversity gradients for East African fishes. Our reconstruction explains the isolated distribution of Nilotic fish species in modern Kenyan rift lakes, Guineo-Congolian mammal species in forests east of the Kenya Rift, and recent incipient vertebrate speciation and local endemism in this region. Climate-driven rearrangements of drainage networks unrelated to tectonic activity contributed significantly to the assembly of species diversity and modern faunas in the East African biodiversity hotspot.

Most of the Earth’s biodiversity is concentrated in the tropics. While the ultimate causes of this geographic pattern remain to be established, ongoing anthropogenic impacts in the tropical belt lead to rapid losses of species diversity. Ancient DNA approaches may help in deciphering temporal patterns in the diversification of tropical biota and could potentially provide historical baseline data on the diversity and distribution of species in anthropogenically modified landscapes. However, studies of sedimentary ancient DNA (sedaDNA) are thus far extremely rare in tropical settings and consequently its value as a conservation tool for tropical ecosystems remains to be tested systematically. To address this issue we present meta-genomic records of shot-gun sequenced sedimentary ancient DNA (sedaDNA) from several sediment cores from the equatorial Bwindi-Impenetrable Forest in Uganda. Because Bwindi is one the most diverse rainforests in Africa and its biota is well documented (including endangered species such Mountain Gorilla and Chimpanzee) it is well suited for a baseline study. We describe the taxonomic composition of sedaDNA from Bwindi for the past 2200 years at an average resolution of 50 years – one of the first comprehensive sedaDNA records of plant and animal taxa from a tropical rainforest. We specifically address the following questions: 1) How precisely can the taxonomic level of shotgun-sequenced tropical sediments be resolved at present? 2) What is the effect of temperature, acidity, nutrient availability, elemental and lithological sediment composition, and burial age on the degradation of DNA? Taxonomic assignments are based on three metagenomic classifiers and four reference databases and their reliability tested against local pollen and modern animal occurrence data. We find that 92.3% of our metagenomic data is taxonomically not identifiable due to the substantial underrepresentation of tropical taxa in genomic reference databases. Yet at ordinal level we reconstruct typical afrotropical assemblages, which do not decline in diversity over time. Our comprehensive set of ecological and sedimentological parameters including sediment age, surface water chemistry, pH, soil temperature, sediment density, sediment water and organic matter content, XRF elemental chemistry, nutrient concentrations, and magnetic susceptibility reveals that DNA degradation cannot be explained by any sedimentary parameter alone, is at Bwindi independent of sediment type, and most likely primarily driven by burial age, suggesting that DNA taphonomic models need to be site-specific in tropical environments. The viability of sedaDNA as a conservation-biology tool requires comprehensive genomic surveys of tropical biota to drastically improve the taxonomic representativeness of DNA reference databases.

The Koora Basin (south Kenya Rift) preserves a continental, tropical, one-million-year record of environmental change driven by global climate, regional tectonism and volcanism. Diatom-based reconstructions from Olorgesailie Drilling Project (ODP) cores indicate lakes that expanded and contracted with conductivities ranging between -200 and > 25,000 mS.cm(-1) and pH of 7.9-11.2. Benthic and planktonic diatoms document mostly shallow fresh water between 1 Ma and 870 ka with deeper freshwater lakes from 870 to 470 ka. After the Mid-Brunhes Event at about 430 ka, diatoms record many transgression-regression cycles with both freshwater and saline-alkaline lakes present. Palaeosols also indicate episodes of desiccation and lower water tables. Carbonates and zeolites are present in younger sediments, especially after 400 ka. Many high-lake-level stages correlate with low values in ocean benthic delta O-18 stack data. Most, but not all, low lake levels occurred during higher delta O-18 MIS intervals, suggesting tectonic and/or volcanic events, in addition to climatic forcing, influenced the drainage, outlet heights and accommodation space. The 870-470 ka period of deeper freshwater lakes at Koora correlates well with the neighbouring Lake Magadi pollen record that suggests generally wetter conditions at this time. Wet-dry cycles after 470 ka at Koora developed when the Magadi record indicates a change towards drier conditions, but with many wetter intervals. High lake level periods at Koora also correlate with phases of diatom-inferred flooding at Magadi. Outcrops north of Koora also document several large lakes during deposition of parts of the Olorgesailie Formation prior to -500 ka. The Koora environmental history helps to fill an environmental gap (500-320 ka) encompassing critical changes in hominin lithic technology caused by a hiatus at Olorgesailie. During the first part of this interval (470-390 ka), Koora was occupied by a shallow alkaline lake, suggesting relatively dry conditions. The second part (390-320 ka) was characterised by fluctuating deeper lakes that imply greater variability and wetter conditions. Subsequently, both the Olorgesailie and Koora records indicate variable environments. (C) 2021 Elsevier Ltd. All rights reserved.

Characterizing eastern African environmental variability on orbital timescales is crucial to evaluating the hominin evolutionary response to past climate changes. However, there is a dearth of high-resolution, well-dated records of ecosystem dynamics from eastern Africa that cover long time intervals. In the last 1 Myr, there were significant anatomical and cultural developments in Homo, including the origin of Homo sapiens. There were also major changes in global climatic boundary conditions that may have affected eastern African environments, yet potential linkages remain poorly understood. We developed carbon isotopic records from plant waxes (δ13Cwax) and bulk organic matter (δ13COM) from a well-dated sediment core spanning the last ∼1 Myr extracted from the Koora Basin, located south of the Olorgesailie Basin, in the southern Kenya rift. Our record characterizes the climatic and environmental context for evolutionary events and technological advances recorded in the adjacent Olorgesailie Basin, such as the transition from Acheulean to Middle Stone Age tools by 320 ka. A significant shift toward more C4-dominated ecosystems and arid conditions occurred near the end of the mid-Pleistocene Transition, which indicates a link between equatorial eastern African and high-latitude northern hemisphere climate. Environmental variability increases throughout the mid- to late-Pleistocene, superimposed by precession-paced packets of variability modulated by eccentricity. An interval of particularly high-amplitude climate and environmental variability occurred from ∼275 ka to ∼180 ka, synchronous with evidence for the first H. sapiens fossils in eastern Africa. These results support the 'variability selection hypothesis' that increased environmental variability selected for adaptable traits, behaviors, and technology in our hominin ancestors.