Arrival Of Modern Humans Research Articles

A molecular approach to Neanderthal extinction

The Neanderthal extinction approximately 30kaBP has been a contentious issue in archaeology, where the role of the deteriorating climate and/or the arrival of modern humans (from 40kaBP) could have played a part. By reconstructing the evolutionary and demographic model alongside a palaeo-climatic chronology, this can allow the changing demography over time to be observed, in order to view how the Neanderthals responded to their environment. Such changes in the demography can then be linked to either a significant change in the deterioration of the climate or the arrival of modern humans. This could then allow for the initial trigger behind the Neanderthal extinction to be identified. One way to reconstruct the evolutionary/demographic model is through the use of a Bayesian based software programme known as BEAST (Bayesian Evolutionary Analysis of Sampling Trees). An evolutionary/demographic model has been reconstructed for North American bison (Bison cf. priscus) whereby their decline in population growth was associated with the climate instead of overhunting by modern humans.The long term goal of this study is to reconstruct the Neanderthal evolutionary/demographic model in order to answer the question of the factors behind the Neanderthal extinction. However, as the Neanderthal genetic data is currently limited, the aim of this study is to identify the more practical issues behind the construction of an evolutionary model and then apply this to the Neanderthal dataset. This shall be done by analyses of a bison genetic dataset in BEAST. The results outline the practical issues affecting the potential reconstruction of the Neanderthal evolutionary/demographic model.

Dragon's paradise lost: palaeobiogeography, evolution and extinction of the largest-ever terrestrial lizards (Varanidae).

BackgroundThe largest living lizard species, Varanus komodoensis Ouwens 1912, is vulnerable to extinction, being restricted to a few isolated islands in eastern Indonesia, between Java and Australia, where it is the dominant terrestrial carnivore. Understanding how large-bodied varanids responded to past environmental change underpins long-term management of V. komodoensis populations.Methodology/Principal FindingsWe reconstruct the palaeobiogeography of Neogene giant varanids and identify a new (unnamed) species from the island of Timor. Our data reject the long-held perception that V. komodoensis became a giant because of insular evolution or as a specialist hunter of pygmy Stegodon. Phyletic giantism, coupled with a westward dispersal from mainland Australia, provides the most parsimonious explanation for the palaeodistribution of V. komodoensis and the newly identified species of giant varanid from Timor. Pliocene giant varanid fossils from Australia are morphologically referable to V. komodoensis suggesting an ultimate origin for V. komodoensis on mainland Australia (>3.8 million years ago). Varanus komodoensis body size has remained stable over the last 900,000 years (ka) on Flores, a time marked by major faunal turnovers, extinction of the island's megafauna, the arrival of early hominids by 880 ka, co-existence with Homo floresiensis, and the arrival of modern humans by 10 ka. Within the last 2000 years their populations have contracted severely.Conclusions/SignificanceGiant varanids were once a ubiquitous part of Subcontinental Eurasian and Australasian faunas during the Neogene. Extinction played a pivotal role in the reduction of their ranges and diversity throughout the late Quaternary, leaving only V. komodoensis as an isolated long-term survivor. The events over the last two millennia now threaten its future survival.

New dates and palaeoenvironmental evidence for the Middle to Upper Palaeolithic occupation of Higueral de Valleja Cave, southern Spain

A research programme has been set up at Higueral de Valleja Cave in southern Spain to investigate the late survival and eventual extinction of the southern Iberian Neanderthals and the arrival of modern humans. Of key interest in the first phase of research was to understand the depositional environment in the entrance chamber of the cave and to establish whether palaeoenvironmental and dating samples could be retrieved from the Middle and Upper Palaeolithic sequences. The outcome is a series of OSL, TL and radiocarbon dates showing that the cave was occupied by Neanderthal populations in Marine Isotope Stage (MIS) 3, if not earlier, and by modern human Solutrean populations during the last glacial maximum. Cave sediments provisionally indicate that the lower Middle Palaeolithic sequence (X–VIII) formed in warm and humid environments and the upper sequence (VIII–V) formed when the climate was cooler and drier. The presence of long grass phytoliths and of the small mammals Microtus duodecimcostatus, Microtus brecciensis and Apodemus sylvaticus in the upper sequence indicates that a range of habitat types persisted near the cave including grassland, scrubby vegetation, patchy tree cover and ponds. This raises the possibility that environmental factors were key factors in the late survival of Neanderthal populations at the cave.

Late survival of Neanderthals at the southernmost extreme of Europe

The late survival of archaic hominin populations and their long contemporaneity with modern humans is now clear for southeast Asia. In Europe the extinction of the Neanderthals, firmly associated with Mousterian technology, has received much attention, and evidence of their survival after 35 kyr bp has recently been put in doubt. Here we present data, based on a high-resolution record of human occupation from Gorham's Cave, Gibraltar, that establish the survival of a population of Neanderthals to 28 kyr bp. These Neanderthals survived in the southernmost point of Europe, within a particular physiographic context, and are the last currently recorded anywhere. Our results show that the Neanderthals survived in isolated refuges well after the arrival of modern humans in Europe.

Neandertals

Neandertals

HISTORY OF ARIDLAND VEGETATION AND CLIMATE: A GLOBAL PERSPECTIVE

Summary1. The origin and history of aridlands and their vegetational cover is closely related to geological history, especially in relation to plate tectonics, mountain building, land‐and sea‐level changes and ice ages, and the arrival of modern humans and their subsequent development.2. A close relationship exists between world temperatures and precipitation. Therefore, the development of present‐day zonal, aridland vegetation and climate cannot be divorced from the history of the latest ice age.3. The combined geological and palaeobotanical evidence demonstrate that whilst the origin of modern openland and aridland vegetation went back to the time of the origin of angiosperms during the Cretaceous, its subsequent expansion went hand in hand with the lowering of world temperatures during the Palaeogene and Neogene, when a series of angiospermous families having dominantly herbaceous and openland taxa, as members, appeared successively in the stratigraphic record.4. The successive lowering of world temperatures had the overall effect of reducing precipitation levels all over the globe. Consequently, high rainfall areas, bearing closed forests, became progressively smaller and smaller and the decreased rainfall promoted the evolution and expansion of low biomass, openland and aridland vegetation.5. The break‐up of regional closed forests had started from the middle Miocene but the main expansion of zonal, aridland vegetation, in low and middle latitudes, appears to have taken place, together with the expansion of tundra vegetation, at high latitudes, from the late Pliocene. Glaciations of a magnitude of at least two‐thirds that of the late Pleistocene glacial maxima started to occur about that time, 25 Ma ago.6. The alternations between cold, glacial and warm, interglacial periods, during the late Neogene, especially with increased amplitude during the last 0.4 Ma, allowed less and less time for forest vegetation to expand and stabilize during the warm intervals, with the result that openland and aridland vegetation was able to expand to unprecedented levels.7. Further, as man increased fire frequencies during the late Pleistocene, the relatively fire‐sensitive and mesophytic taxa were selectively eliminated and more and more forests were opened to invasion by openland taxa in low and middle latitudes. Later on, with the clearance of forests for agriculture, the overall effect on vegetation was to create open landscapes which favoured the expansion of openland taxa at low, middle and high latitudes, during an interglacial, that is, the Holocene, a feature that is unprecedented in the entire earlier geological record.