ORCID Profile
0000-0002-0413-8133
Current Organisation
Griffith University
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Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-09-2020
Abstract: Ancient human footprints in Saudi Arabia provide snapshot of Arabian ecology 120,000 years ago.
Publisher: Springer Science and Business Media LLC
Date: 09-2021
DOI: 10.1038/S41586-021-03863-Y
Abstract: Pleistocene hominin dispersals out of, and back into, Africa necessarily involved traversing the erse and often challenging environments of Southwest Asia 1–4 . Archaeological and palaeontological records from the Levantine woodland zone document major biological and cultural shifts, such as alternating occupations by Homo sapiens and Neanderthals. However, Late Quaternary cultural, biological and environmental records from the vast arid zone that constitutes most of Southwest Asia remain scarce, limiting regional-scale insights into changes in hominin demography and behaviour 1,2,5 . Here we report a series of dated palaeolake sequences, associated with stone tool assemblages and vertebrate fossils, from the Khall Amayshan 4 and Jubbah basins in the Nefud Desert. These findings, including the oldest dated hominin occupations in Arabia, reveal at least five hominin expansions into the Arabian interior, coinciding with brief ‘green’ windows of reduced aridity approximately 400, 300, 200, 130–75 and 55 thousand years ago. Each occupation phase is characterized by a distinct form of material culture, indicating colonization by erse hominin groups, and a lack of long-term Southwest Asian population continuity. Within a general pattern of African and Eurasian hominin groups being separated by Pleistocene Saharo-Arabian aridity, our findings reveal the tempo and character of climatically modulated windows for dispersal and admixture.
Publisher: Canadian Science Publishing
Date: 10-2015
Abstract: Gut capacity is an important factor in digestive physiology and is often measured as dry matter fill (DMF) following dissection, which prevents repeated measures in the same animal. It was proposed to calculate DMF from food intake, digestibility, and gut mean retention time (MRT), but empirical tests of this are few. We calculated DMF from intake, digestibility, and the MRT of small-particle (1 mm) and large-particle (20 mm) markers in 20 sheep (Ovis aries L., 1758) fed at different intake levels and compared results with DMF at dissection at the end of the feeding trial. MRT for smaller particles was significantly shorter than for larger particles (34.4 ± 6.1 vs. 42.5 ± 7.6 h, respectively). Correspondingly, DMF calculated from smaller particles (0.98 ± 0.27 kg) was significantly lower than DMF calculated from larger particles (1.20 ± 0.30 kg). The latter was not significantly different from DMF measured at dissection (1.18 ± 0.34 kg). These results suggest that DMF can be estimated from measures of digestive physiology. The choice of particle marker to determine MRT is crucial for the accuracy of the proxy. In ruminants, where small particles are consistently eliminated faster than larger particles, considerations of marker particle size are particularly important.
Publisher: Wiley
Date: 14-01-2018
DOI: 10.1111/JBI.13165
Publisher: The Company of Biologists
Date: 11-2015
DOI: 10.1242/JEB.128165
Abstract: Fundamental differences in methane (CH4) production between macropods (kangaroos) and ruminants have been suggested and linked to differences in the composition of the forestomach microbiome. Using six western grey kangaroos (Macropus fuliginosus) and four red kangaroos (Macropus rufus), we measured daily absolute CH4 production in vivo as well as CH4 yield (CH4 per unit of intake of dry matter, gross energy or digestible fibre) by open-circuit respirometry. Two food intake levels were tested using a chopped lucerne hay (alfalfa) diet. Body mass-specific absolute CH4 production resembled values previously reported in wallabies and non-ruminant herbivores such as horses, and did not differ with food intake level, although there was no concomitant proportionate decrease in fibre digestibility with higher food intake. In contrast, CH4 yield decreased with increasing intake, and was intermediate between values reported for ruminants and non-ruminant herbivores. These results correspond to those in ruminants and other non-ruminant species where increased intake (and hence a shorter digesta retention in the gut) leads to a lower CH4 yield. We hypothesize that rather than harbouring a fundamentally different microbiome in their foregut, the microbiome of macropods is in a particular metabolic state more tuned towards growth (i.e. biomass production) rather than CH4 production. This is due to the short digesta retention time in macropods and the known distinct ‘digesta washing’ in the gut of macropods, where fluids move faster than particles and hence most likely wash out microbes from the forestomach. Although our data suggest that kangaroos only produce about 27% of the body mass-specific volume of CH4 of ruminants, it remains to be modelled with species-specific growth rates and production conditions whether or not significantly lower CH4 amounts are emitted per kg of meat in kangaroo than in beef or mutton production.
Publisher: Elsevier BV
Date: 08-2019
Publisher: Springer Science and Business Media LLC
Date: 11-08-2022
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/ZO14058
Abstract: Daily torpor, a short-term reduction in body temperature and metabolism, is an energy-saving strategy that has been interpreted as an adaptation to unpredictable resource availability. However, the effect of food-supply variability on torpor, separately from consistent food restriction, remains largely unexamined. In this study, we investigated the effect of unpredictable food availability on torpor in stripe-faced dunnarts (Sminthopsis macroura). After a control period of ad libitum feeding, dunnarts were offered 65% of their average daily ad libitum intake over 31 days, either as a constant restriction (i.e. as equal amount of food offered each day) or as an unpredictable schedule of feed offered, varied daily as 0%, 30%, 60%, 100% or 130% of ad libitum. Both feeding groups had increased torpor-bout occurrences (as a proportion of all dunnarts on a given day) and torpor-bout frequency (average number of bouts each day) when on a restricted diet compared with ad libitum feeding, but torpor frequency did not differ between the consistently restricted and unpredictably restricted groups. Most importantly, torpor occurrence and daily bout frequency by the unpredictably restricted group appeared to change in direct association with the amount of food offered on each day torpor frequency was higher on days of low food availability. Our data do not support the interpretation that torpor is a response to unpredictable food availability per se, but rather that torpor allowed a rapid adjustment of energy expenditure to manage daily fluctuations in food availability.
Publisher: The Company of Biologists
Date: 10-05-0010
DOI: 10.1242/BIO.012179
Abstract: What is the most humane way to kill hibians and small reptiles that are used in research? Historically, such animals were often killed by cooling followed by freezing, but this method was outlawed by ethics committees because of concerns that ice-crystals may form in peripheral tissues while the animal is still conscious, putatively causing intense pain. This argument relies on assumptions about the capacity of such animals to feel pain, the thermal thresholds for tissue freezing, the temperature-dependence of nerve-impulse transmission and brain activity, and the magnitude of thermal differentials within the bodies of rapidly-cooling animals. A review of published studies casts doubt on those assumptions, and our laboratory experiments on cane toads (Rhinella marina) show that brain activity declines smoothly during freezing, with no indication of pain perception. Thus, cooling followed by freezing can offer a humane method of killing cane toads, and may be widely applicable to other ectotherms (especially, small species that are rarely active at low body temperatures). More generally, many animal-ethics regulations have little empirical basis, and research on this topic is urgently required in order to reduce animal suffering.
Publisher: Frontiers Media SA
Date: 18-04-2023
DOI: 10.3389/FEARC.2023.1080785
Abstract: Climate change played a major role in shaping regional human-environment interactions in Africa during the late Pleistocene-Holocene, but this topic has not been exhaustively studied, particularly in eastern Africa. While there is growing evidence that the coastal and island settings in this region played a critical role in human evolution, combined archaeological and palaeoenvironmental studies have tended to focus on the arid interior and show the dominance of grasslands with patches of closed and open woodlands during the last 20,000 years. Here, we present stable carbon and oxygen isotope analyses of zooarchaeological remains (n = 229) recovered from Kuumbi Cave, Zanzibar Island, spanning the last glacial period and the Holocene (20,000 to 500 cal. BP). Our data demonstrate that the vicinity of Kuumbi Cave was consistently covered by mosaic habitats, dominated by forests and small patches of open woodland and grassland. The inhabitants of Kuumbi Cave exploited these erse tropical habitats even after the regional arrival of agriculture. We suggest that the stable coastal forest mosaic habitats acted as a refugium for foragers during glacial periods and that the Iron Age inhabitants of Kuumbi Cave were not food producers migrating from the interior, but rather Indigenous foragers interacting with food production.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Frontiers Media SA
Date: 11-01-2022
DOI: 10.3389/FEART.2021.771683
Abstract: The small size and relatively challenging environmental conditions of the semi-isolated Maltese archipelago mean that the area offers an important case study of societal change and human-environment interactions. Following an initial phase of Neolithic settlement, the “Temple Period” in Malta began ∼5.8 thousand years ago (ka), and came to a seemingly abrupt end ∼4.3 ka, and was followed by Bronze Age societies with radically different material culture. Various ideas concerning the reasons for the end of the Temple Period have been expressed. These range from climate change, to invasion, to social conflict resulting from the development of a powerful “priesthood.” Here, we explore the idea that the end of the Temple Period relates to the 4.2 ka event. The 4.2 ka event has been linked with several ex les of significant societal change around the Mediterranean, such as the end of the Old Kingdom in Egypt, yet its character and relevance have been debated. The Maltese ex le offers a fascinating case study for understanding issues such as chronological uncertainty, disentangling cause and effect when several different processes are involved, and the role of abrupt environmental change in impacting human societies. Ultimately, it is suggested that the 4.2 ka event may have played a role in the end of the Temple Period, but that other factors seemingly played a large, and possibly predominant, role. As well as our chronological modelling indicating the decline of Temple Period society in the centuries before the 4.2 ka event, we highlight the possible significance of other factors such as a plague epidemic.
Publisher: Frontiers Media SA
Date: 17-11-2021
DOI: 10.3389/FEART.2021.769107
Abstract: The second millennium CE in Europe is known for both climatic extremes and bloody conflict. Europeans experienced the Medieval Warm Period and the Little Ice Age, and they suffered history-defining violence like the Wars of the Roses, Hundred Years War, and both World Wars. In this paper, we describe a quantitative study in which we sought to determine whether the climatic extremes affected conflict levels in Europe between 1,005 and 1980 CE. The study involved comparing a well-known annual historical conflict record to four published temperature reconstructions for Central and Western Europe. We developed a Bayesian regression model that allows for potential threshold effects in the climate–conflict relationship and then tested it with simulated data to confirm its efficacy. Next, we ran four analyses, each one involving the historical conflict record as the dependent variable and one of the four temperature reconstructions as the sole covariate. Our results indicated that none of the temperature reconstructions could be used to explain variation in conflict levels. It seems that shifts to extreme climate conditions may have been largely irrelevant to the conflict generating process in Europe during the second millennium CE.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Frontiers Media SA
Date: 24-08-2022
DOI: 10.3389/FEART.2022.786829
Abstract: The term “extreme event” is commonly used to describe high-impact, unanticipated natural events, like floods, tsunamis, earthquakes, and volcanic eruptions. It first appeared in the scientific literature in the 1950s and has since spread to disciplines as erse as economics, psychology, medicine, and engineering. The term is increasingly being applied to the study of historical, prehistorical, and deep-time events across a broad range of scales, and it is widely acknowledged that such events have had profound impacts on the Earth’s bio ersity and cultures. Understandably, then, how people think about, define, and study extreme events varies considerably. With extreme events expected to become more frequent, longer lasting, and more intense in the coming decades as a result of global warming, the differing extreme event definitions—both across and within disciplines—is likely to lead to confusion among researchers and pose significant challenges for predicting and preparing for extreme events and their impacts on natural and social systems. With this in mind, we conducted a systematic quantitative review of 200 randomly selected, peer-reviewed “extreme event” research papers (sourced from Web of Science, accessed January 2020) from the biological, societal, and earth sciences literature with the aim of quantifying several pertinent features of the research s le. On the one hand, our analysis found a great deal of variability among extreme event papers with respect to research interests, themes, concepts, and definitions. On the other hand, we found a number of key similarities in how researchers think about and study extreme events. One similarity we encountered was that researchers tend to view extreme events within a particular temporal context and quite often in terms of rates of change. Another similarity we encountered was that researchers often think of and study extreme events in terms of risks, vulnerabilities, and impacts. The similarities identified here may be useful in developing a common and comprehensive definition of what constitutes an extreme event, and should allow for more comparative research into extreme events at all spatio-temporal scales which, we predict, will provide important new insights into the nature of extreme events.
Publisher: SAGE Publications
Date: 17-08-2020
Abstract: Between 10 and six thousand years ago the Arabian Peninsula saw the most recent of the ‘Green Arabia’ periods, when increased rainfall transformed this generally arid region. The transition to the Neolithic in Arabia occurred during this period of climatic amelioration. Various forms of stone structures are abundant in northern Arabia, and it has been speculated that some of these dated to the Neolithic, but there has been little research on their character and chronology. Here we report a study of 104 ‘mustatil’ stone structures from the southern margins of the Nefud Desert in northern Arabia. We provide the first chronometric age estimate for this type of structure – a radiocarbon date of ca. 5000 BC – and describe their landscape positions, architecture and associated material culture and faunal remains. The structure we have dated is the oldest large-scale stone structure known from the Arabian Peninsula. The mustatil phenomenon represents a remarkable development of monumental architecture, as hundreds of these structures were built in northwest Arabia. This ‘monumental landscape’ represents one of the earliest large-scale forms of monumental stone structure construction anywhere in the world. Further research is needed to understand the function of these structures, but we hypothesise that they were related to rituals in the context of the adoption of pastoralism and resulting territoriality in the challenging environments of northern Arabia.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 20-07-2021
DOI: 10.1007/S12520-021-01365-6
Abstract: Studies of modern carnivore accumulations of bone (i.e., neo-taphonomy) are crucial for interpreting fossil accumulations in the archaeological and paleontological records. Yet, studies in arid regions have been limited in both number and detailed taphonomic data, prohibiting our understanding of carnivore bone-accumulating and -modifying behavior in dry regions. Here, we present a taphonomic analysis of an impressive carnivore-accumulated bone assemblage from the Umm Jirsan lava tube in the Harrat Khaybar region, Saudi Arabia. The size and composition of the bone accumulation, as well as the presence of hyena skeletal remains and coprolites, suggest that the assemblage was primarily accumulated by striped hyena ( Hyaena hyaena ). Our findings (1) identify potentially useful criteria for distinguishing between accumulations generated by different species of hyenas (2) emphasize the need for neo-taphonomic studies for capturing the full variation in carnivore bone-accumulating and modifying behavior (3) suggest that under the right settings, striped hyena accumulations can serve as good proxies for (paleo)ecology and livestock practices and (4) highlight the potential for future research at Umm Jirsan, as well as at the numerous nearby lava tube systems. We encourage continued neo-taphonomic efforts in regions important in human prehistory, particularly in arid zones, which have received little research attention.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/RJ15083
Abstract: Details of the energy (food) requirements of domestic herbivores are essential for predicting grazing pressures and subsequent ecological impacts on rangelands. However, these details are lacking for some of the more recently introduced sheep breeds to Australia, such as the Dorper breed sheep, which are principally meat sheep, and it is uncertain how they compare with the traditional Merino, a wool-breed, sheep. We used the doubly labelled water method to compare the field metabolic rate and water turnover rate of Dorpers and Merinos grazing together in a small holding paddock in a typical rangeland environment. We found no significant differences in field metabolic rate (Dorpers 481 ± 125 kJ and Merinos 500 ± 109 kJ kg–0.73 day–1) or water turnover rate (Dorpers 397 ± 57 mL and Merinos 428 ± 50 mL kg–0.8 day–1). As such we conclude that under controlled conditions with limited movement and ready access to feed and water, dry sheep equivalent of 1 is appropriate for Dorpers (that is, one Dorper ewe had a grazing requirement equal to one standard, dry Merino wether). However, we also found that the field metabolic rate for Merinos under these conditions was only around half that measured in published studies for animals ranging freely in a large paddock system. This suggests that more work is needed to fully appreciate the energetic and grazing impacts of Dorpers versus Merinos under more realistic grazing conditions (e.g. large paddock systems) where feed and water are more spread. It also highlights limitations of the current dry sheep equivalent rating system, which has been derived from laboratory measures of sheep metabolic rates.
Publisher: Elsevier BV
Date: 05-2016
Publisher: Springer Science and Business Media LLC
Date: 09-04-2018
Publisher: Cambridge University Press (CUP)
Date: 20-03-2020
DOI: 10.1017/QUA.2020.6
Abstract: Over the past decade, a growing interest has developed on the archaeology, palaeontology, and palaeoenvironments of the Arabian Peninsula. It is now clear that hominins repeatedly dispersed into Arabia, notably during pluvial interglacial periods when much of the peninsula was characterised by a semiarid grassland environment. During the intervening glacial phases, however, grasslands were replaced with arid and hyperarid deserts. These millennial-scale climatic fluctuations have subjected bones and fossils to a dramatic suite of environmental conditions, affecting their fossilisation and preservation. Yet, as relatively few palaeontological assemblages have been reported from the Pleistocene of Arabia, our understanding of the preservational pathways that skeletal elements can take in these types of environments is lacking. Here, we report the first widespread taxonomic and taphonomic assessment of Arabian fossil deposits. Novel fossil fauna are described and overall the fauna are consistent with a well-watered semiarid grassland environment. Likewise, the taphonomic results suggest that bones were deposited under more humid conditions than present in the region today. However, fossils often exhibit significant attrition, obscuring and fragmenting most finds. These are likely tied to wind abrasion, insolation, and salt weathering following fossilisation and exhumation, processes particularly prevalent in desert environments.
Publisher: Springer Science and Business Media LLC
Date: 10-01-2022
Publisher: Springer Science and Business Media LLC
Date: 29-10-2018
DOI: 10.1038/S41559-018-0698-9
Abstract: Despite its largely hyper-arid and inhospitable climate today, the Arabian Peninsula is emerging as an important area for investigating Pleistocene hominin dispersals. Recently, a member of our own species was found in northern Arabia dating to ca. 90 ka, while stone tools and fossil finds have hinted at an earlier, middle Pleistocene, hominin presence. However, there remain few direct insights into Pleistocene environments, and associated hominin adaptations, that accompanied the movement of populations into this region. Here, we apply stable carbon and oxygen isotope analysis to fossil mammal tooth enamel (n = 21) from the middle Pleistocene locality of Ti's al Ghadah in Saudi Arabia associated with newly discovered stone tools and probable cutmarks. The results demonstrate productive grasslands in the interior of the Arabian Peninsula ca. 300-500 ka, as well as aridity levels similar to those found in open savannah settings in eastern Africa today. The association between this palaeoenvironmental information and the earliest traces for hominin activity in this part of the world lead us to argue that middle Pleistocene hominin dispersals into the interior of the Arabian Peninsula required no major novel adaptation.
Publisher: Elsevier BV
Date: 2020
Publisher: Springer Science and Business Media LLC
Date: 18-06-2014
DOI: 10.1007/S00359-014-0920-4
Abstract: We examined the effect of an abrupt change in diet fibre content on the feed intake, gastrointestinal morphology and utilisation of gastroliths by a small (ca. 40 g body mass) herbivorous bird, the King Quail (Coturnix chinensis). King Quail were acclimated for 14 days on a low-fibre (LF) pullet starter diet. Following acclimation, half the quail population was immediately switched to a 23% wood-shaving diluted high-fibre (HF) diet for a further 14 days. Contrary to expectations, we found no differences in feed intake, gut morphology or gastrolith mass between the LF- and HF-fed quail. However, when switched from the LF to HF diet, the quail commenced feed-sorting behaviours that permitted HF-fed animals to maintain body condition (mass, abdominal fat mass) without adjustments to intestinal organ sizes or gastrolith mass. Feed sorting was initiated only after exposure to the HF diet, which corresponded with an immediate reduction in food intake, suggesting that the sorting behaviour was cued by a physiological challenge associated with the HF diet. This challenge apparently induced preferential sorting behaviour and was possibly due to abrupt changes in the rate of food passage, impacting satiation or other internal cues.
Publisher: Springer Science and Business Media LLC
Date: 16-02-2021
DOI: 10.1038/S41467-021-21201-8
Abstract: The disappearance of many North American megafauna at the end of the Pleistocene is a contentious topic. While the proposed causes for megafaunal extinction are varied, most researchers fall into three broad c s emphasizing human overhunting, climate change, or some combination of the two. Understanding the cause of megafaunal extinctions requires the analysis of through-time relationships between climate change and megafauna and human population dynamics. To do so, many researchers have used summed probability density functions (SPDFs) as a proxy for through-time fluctuations in human and megafauna population sizes. SPDFs, however, conflate process variation with the chronological uncertainty inherent in radiocarbon dates. Recently, a new Bayesian regression technique was developed that overcomes this problem—Radiocarbon-dated Event-Count (REC) Modelling. Here we employ REC models to test whether declines in North American megafauna species could be best explained by climate changes, increases in human population densities, or both, using the largest available database of megafauna and human radiocarbon dates. Our results suggest that there is currently no evidence for a persistent through-time relationship between human and megafauna population levels in North America. There is, however, evidence that decreases in global temperature correlated with megafauna population declines.
Publisher: Copernicus GmbH
Date: 03-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-2844
Abstract: & & The late Quaternary saw the extinction of a great number of the world& #8217 s megafauna (those animals & kg), an event unprecedented in 65 million-years of mammalian evolution. Extinctions were notably severe in North America where 37 genera (~80%) of megafauna disappeared by around the late Pleistocene/Holocene boundary (~11.7 thousand-years-ago, or ka). Scholars have typically attributed these extinctions to overhunting by rapidly expanding human populations (i.e., overkill), climate change, or some combination of the two. Testing human- and climate-driven extinctions hypotheses in North America, however, has proven difficult given the apparent concurrency of human arrival in the Americas& #8212 more specifically, the emergence of Clovis culture (~13.2& #8211 .9 ka)& #8212 and terminal Pleistocene climate changes such as the abrupt warming of the B& #248 lling-Aller& #248 d interstadial (B-A ~14.7& #8211 .9 ka) or near-glacial conditions of the Younger-Dryas stadial (YD 12.9& #8211 .7 ka). Testing these hypotheses will, therefore, require the analysis of through-time relationships between climate change and megafauna and human population dynamics. To do so, many researchers have used summed probability density functions (SPDFs) as a proxy for through-time fluctuations in human and megafauna population sizes. SPDFs, however, conflate process variation with the chronological uncertainty inherent in radiocarbon dates. Recently, a new Bayesian regression technique was developed that overcomes this problem& #8212 Radiocarbon-dated Event-Count (REC) modelling. Using the largest available dataset of megafauna and human radiocarbon dates, we employed REC models to test whether declines in North American megafauna species could be best explained by climate change (temperature), increases in human population densities, or both. On the one hand, we reasoned that if human overhunting drove megafauna extinctions, there would be a negative correlation between human and megafauna population densities. On the other hand, if climate change drove megafauna extinctions, there would be a correlation between our temperature proxy (i.e., the North Greenland Ice Core Project [NGRIP] & #948 & sup& & /sup& O record) and megafauna population densities. We found no correlation between our human and megafauna population proxies and, therefore, no support for simple models of overkill. While our findings do not preclude humans from having had an impact& #8212 for ex le, by interrupting megafauna subpopulation connectivity or performing a coup de gr& #226 ce on already impoverished megafauna& #8212 they do suggest that growing populations of & #8220 big-game& #8221 hunters were not the primary driving force behind megafauna extinctions. We did, however, consistently find a significant, positive correlation between temperature and megafauna population densities. Put simply, decreases in temperature correlated with declines in North American megafauna. The timing of megafauna population declines and extinctions suggest that the unique conditions of the YD& #8212 i.e., abrupt cooling, increased seasonality and CO& sub& & /sub& , and major vegetation changes& #8212 layed a key role in the North American megafauna extinction event.& &
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-9980
Abstract: The Saharo-Arabian desert is part of the largest near-continuous chain of drylands stretching from north-western Africa to the northern China. This harsh and often hyper-arid belt acts as a transition zone separating major biogeographic realms, including the Palearctic, Afrotropics and Indomalayan. This aridity is thought responsible for the creation of unique geographic endemism between Africa and Eurasia. However, there are no direct hydroclimate records from the Arabian hyper-arid interior before the mid-Pleistocene, leaving the terrestrial hydroclimate and the role of Arabia as a biogeographic crossroads or barrier largely unknown.We use desert speleothems preserved from the northern Arabian interior to identify past humid phases over the last 8 million years. These are particularly useful terrestrial climate archives as they act as underground rain gauges, requiring a minimum of ~300 mm a-1 precipitation, pedogenesis and vegetation cover to form. Moreover, they can be accurately and precisely dated and are subsequently a valuable tool in identifying past large-scale hydrological and vegetation changes in ancient drylands. Our data reveal evidence of multiple & #8216 windows of opportunity& #8217 of climate amelioration, allowing biogeographic exchange and dispersals to occur across the Arabian hyper-arid zone. Further, the novel analyses of the isotopic composition (d18O and d2H) of speleothem fluid inclusion waters, representing & #8216 fossil rainwater& #8217 , reveal the diminishing influence of tropical rain-belt precipitation in Arabia across Earth& #8217 s transition from a largely & #8216 ice-free& #8217 northern hemisphere to an & #8216 ice-age& #8217 world. The extent of Arabian aridity may thus be important in controlling biogeographic dispersals through the Arabian corridor, becoming increasingly less favourable through time. This is supported by fossil evidence which suggest that exchange between biogeographic regions across the Old World Savannah Biome were favoured in the Late Miocene, but became increasingly latitudinally fragmented from the Pliocene onwards. These results have significant implications for understanding the drivers of dryland aridity in non-polar deserts globally.&
No related grants have been discovered for Mathew Stewart.