Pandas,
Dodos and Neanderthals: endangered species in the Quaternary red data book
Clive Finlayson, The Gibraltar
Museum, 18-20 Bomb House Lane, Gibraltar & Department of Anthropology, University of
Toronto, Canada
Email: jcfinlay@gibnet.gi
Geraldine Finlayson & Darren A.
Fa, The Gibraltar Museum, 18-20 Bomb House Lane, Gibraltar
---------------------------------------
This paper examines a range of issues concerning the neanderthal extinction and the colonization of Eurasia by modern humans from an evolutionary ecological perspective. It then provides, from a basis of evolutionary ecology theory, a hypothesis for the Neanderthal extinction and the modern human colonization, embedded within a broader framework of colonizations and extinctions by Pleistocene hominids, and makes testable predictions.
The first part of the paper evaluates
the evidence for certain aspects of neanderthal and modern human biology that are
currently well established in the literature:
The second part develops a model of neanderthal-modern human biogeography. The following conclusions are reached:
1. An
external or environmental axis. It is the frequency of
climatic oscillations, therefore climatic variability, coupled with their intensity that
is responsible for the fragmentation of neanderthal habitats and the expansion of modern
human habitats. Temporal lags and cumulative effects are crucial in understanding the
phenomenon.
2. An
internal or within-population axis. The crucial underlying,
non-deterministic, factor that led to the extinction of the neanderthals (and probably
worse so in earlier hominids) and the colonization of the moderns was the scale of
operation. The physical, ecological and behavioural attributes of the moderns allowed them
to operate at higher spatio-temporal scales than neanderthals and enabled them to deal
more effectively with the climatic instability of OIS 3.
The
Genetic Legacy of the Quaternary Ice Ages: Inferring glacial refugia and historical
migrations with molecular phylogenies
Godfrey M
Hewitt, Department of Biology University of East Anglia, Norwich, United Kingdom.
--------------------------
Palaeoclimatic research is particularly active at present, producing startling new data and increasingly coherent explanations. The climate became cooler through the Tertiary with frequent oscillations leading to the series of major ice ages of the Quaternary. Evidence for such global fluctuations in climate comes particularly from cores of the sea bed, lake bottoms and ice sheets, and as more long cores become available it is possible to gauge the effects of climatic changes on organisms around the world.
These severe climatic oscillations produced great changes in species distributions, and these can be described in some detail from the fossil record, particularly for pollen and beetles in Europe and North America. Species went extinct over large parts of their range, some dispersed to new locations, some survived in refugia and then expanded again. In warmer parts species descended from mountains, tropical rainforest was restricted and fragmented, and there was extension of deserts and savannah. Then they reversed, and these processes must have occurred repeatedly.
To better understand our present biota we may ask, where were the refugia and which were the most likely migration routes? Such events would have had genetic consequences, and of particular interest are those produced by the dynamics of colonization, where rapid expansion by the leading edge model should produce areas of reduced genomic variability. Also during a range change a retreating rear edge would suffer shrinkage and fragmentation causing bottlenecks. In southern temperate regions and the tropics, mountain blocks would allow slower altitudinal shifts in range, which would tend to retain genetic diversity, and also cause subdivision of the species genome.
Modern DNA technology allows genetic differences to be measured as single base changes in many individuals, and a variety of sequences have been employed. This new type of data allows the genetic relationship among individuals and the divergence of lineages to be assessed. Intraspecific phylogenies for particular DNA sequences can be used to make inferences about the history of a species, particularly when placed in the spatial context of past and present ranges of the species. New methods such as DNA distance phenograms, sequence mismatch comparisons, nested clade analysis and spanning haplotype networks are available, which assist this inference. The interpretation of these phylogenies becomes much stronger when combined with knowledge of present species substructure and hybrid zones, and relevant palaeoclimatic, fossil and geographic information.
These approaches have been applied to a number of European species with adequate DNA data sets to deduce from which ice age refugia particular genomes emerged to cover their present distribution. These provide tests of expectations, novel insights into species colonization, and unexpected genetic subdivision and mixture of species. Three paradigm patterns are evident and these may be related to other European species distributions to assess their generality.
Comparable data sets and analyses are becoming available in other parts of the world, particularly for species in North America. Bearing in mind the differences from Europe in geography and palaeoclimate, several similarities in genome diversity and structure are apparent. Species from different biomes in the Arctic, Tropics and Oceans are also being investigated in this way with interesting results. These studies also contribute to understanding the processes and rates of speciation over the Pleistocene.
Late Pleistocene
environmental upheavals in Europe and the setting of modern vertebrate communities
Jacques
Blondel, CEFE-CNRS, 34293 Montpellier cedex, France
A large wealth of data recently accumulated from fields as diverse as palaeobiology, palaeoclimatology, molecular phylogenetics, population genetics and evolutionary ecology completely renewed pictures on the consequences on living organisms of global climate fluctuations during the past 2.5 million years. The reconstruction of palaeoenvironments and the identification of major distributional shifts of vegetation belts and habitats in response to climate changes provided a new perspective on differentiation and extinction rates as well as on the establishment of modern floras and faunas. This history should help interpret the ecological context in which early humans lived and evolved in the late Pleistocene because there is no reason that the distribution of hominids should differ much from that of many contemporary large mammals, especially as concern their splitting and divergence in small isolated refugia.
The first part of the paper will
consider at a macro-ecological scale the
consequences of climatic fluctuations on the evolution and distribution of biotas in
Europe. I will focus on differentiation and extinction processes as a result of shifts and
fragmentation of major vegetation belts. At timescales of 103-105
years, the distribution and composition of biotas have changed continuously with glacial
conditions having dominated the Pleistocene so that present communities had a short
history, of an order of magnitude of a few thousand years at the most. Actually, the
Quaternary should be viewed as “a cold epoch interrupted periodically by catastrophic
warm events - the brief interglacials with climate similar today” (M.B. Davis). Three
points will be briefly considered. First, patterns of large scale back and forth
distributional shifts of species. These shifts across Europe can be considered as
migrations sensu stricto, the only difference with classical annual migration
of birds being that the temporal scale of migratory cycles was considerably larger. These
large-scale migrations resulted in gene swamping and mixture of genomes in the
glacial (= “winter”) refugia, and reduced opportunities of allopatric speciation
in many groups of animals, e.g. birds. Two, extinction processes have been much more
severe in the western Palaearctic than in the two other temperate blocks of similar size
of the Northern Hemisphere, namely the Eastern Palaearctic and Eastern North America,
because the massive east-west barriers of the western Palaearctic prevented organisms to
find refuge in tropical areas. Large and repeated habitat changes at the late Pleistocene
have undoubtedly accelerated extinction rates of vertebrates of the western Palaearctic,
just as they did in North America. This gives an idea of the dramatic ecological
conditions Neanderthals presumably were confronted to, and which may have precipitated
them to extinction. Examples will be given of the consequences of differential extinction
processes in the three temperate regions of the Northern Hemisphere on the structure,
ecology and dynamics of extant species assemblages. Third, differentiation at the
population and species levels will be briefly examined. Although recent studies using
molecular systematics based on mtDNA provide evidence that many species are much more
ancient than formerly thought and are rooted in the late Pliocene, environmental changes
of the Pleistocene certainly had much impact on extant species diversity and extremely
rapid differentiation leading to speciation has been demonstrated in several groups of
lizards and fish colonizing new habitats. Differentiation in refugia during glacial
periods and subsequent range expansions of distinct phylogeographical lineages explain
extant patterns of genetic structuration in Europe of several groups of plants and animals
(birds, mammals, amphibians), including man. Modern DNA techniques allow us to know from
which refugia particular haplotypes emerged and to reconstruct postglacial colonization
routes. However, endemism rates differ much according to groups, mostly as a result of
taxon-specific variation in dispersal ranges.
Palaeontological and archaeological records give a nice insight in the fauna and species assemblages of southern Europe at the late Pleistocene (OIS3). There data provide evidence that the accumulation of several vegetation belts and their associated faunas in refugia of the Mediterranean during pleniglacials resulted in a mosaic of habitats at the scale of landscapes and the coexistence of species of different biogeographic origin. The diversity of both geography and conditions of temperature and moisture within the Mediterranean during glacial periods allowed for the coexistence on a small spatial scale of all the European vegetation belts and their associated faunas. This is consistent with palaeontological data reporting on disparate mixtures of birds species including steppe species, tundra species and Mediterranean saxicolous species found in the same fossil deposits of Würm II (70,000 BP) in southern France. Examples will be given of species assemblages contemporary of Neanderthals using the faunas of large mammals and sea birds, including Pinguinus impennis, which used to breed in large colonies along the coasts of Mediterranean Europe.
In the second part of the paper, I will
focus on micro-ecological variation of populations. Patterns of micro-evolutionary
responses of organisms to climate and environmental changes that have repeatedly occurred
during the Pleistocene, and which were remarkably rapid at each large climatic change, may
tentatively be investigated from current studies on the responses of populations to
changes in habitats and climate. This should give an insight on what Pleistocene
communities, including Palaeolithic humans, have experienced because the cumulative
effects of cold periods presumably fragmented populations in small units, becoming
increasingly isolated, and thus particularly prone to extinction as a result of the
“extinction vortex”. One important issue in evolutionary ecology which might
have been crucial for Neanderthals is the subdivision of populations as a result of
habitat fragmentation and/or climate change. This process is conducive to the splitting of
populations in metapopulations whose survival probabilities decrease as landscapes become
increasingly fragmented. Using long-term studies of bird populations I will show how
contrasting regimes of selection, presumably similar to those that occur at each climatic
change, result in rapid changes in suite of life history traits in spite of a substantial
amount of gene flow. I will examine how proximate and ultimate factors determine
phenotypic variation, reactions norms and local specialisation in relation to small-scale
environmental variation. This will give an idea of the extent and speed of life history
evolution as a response to environmental changes, just the kind of change that presumably
occurred many times during the Pleistocene at each climatic change. This question has been
addressed in the Mediterranean region, using blue tit (Parus caeruleus) populations living in habitat
patches dominated either by deciduous (Quercus
humilis) or evergreen (Q. ilex) oaks, which
strongly differ in the timing and abundance of food resources. First, I shall examine the
extent of phenotypic variation and local differentiation of fitness-related traits at the
scale of habitat mosaics within two landscapes, one in mainland southern France and one on
the island of Corsica. Then I will show that the observed phenotypic variation is an
ultimate response to local selection regimes and results in local adaptation. On the
mainland molecular studies at the scale of a landscape support the hypothesis of a
source-sink population structure whereas in a similar geographic configuration of habitats
in Corsica, there was a higher phenotypic variation and a higher degree of population
differentiation on a scale which is usually smaller than the dispersal range of blue tits.
This difference between the mainland and Corsica, with a much higher degree of
differentiation in the latter, is interpreted as resulting from reduced dispersal ranges
of island birds and supports the divergence-with-gene-flow model of speciation. It could
be that the morphological, behavioural and demographical divergence between two
conspecific populations of birds only 25 km apart are as large as the differences between
Neanderthals and modern humans!
Addressing question on the response of
organisms to large environmental changes is really challenging because there is widespread
concern that the earth’s climate will warm up by at least 3°C within this century.
Such change is comparable to the shifts in climate that accompanied the advances and
retreats of glaciers during the Pleistocene. It will have drastic effects on the
distribution and diversity of living beings.
The Neanderthal Landscape – An Overview of the
Results of the Stage Three Project.
----------------------------------
Three years ago, one of the authors (Tjeerd van Andel) presented an account of the approaches and underlying concepts behind the Stage Three Project (Oxygen Isotope Stage 3 (OIS-3): 60,000-25,000 cal. BP), and this paper represents an up-date. Now in its fifth and final phase, the Project has generated detailed simulations of the European climate and landscape during a typical warm Interstadial (approx. 40,000 calendar years BP) and, for comparison, the extreme cold climate of the Last Glacial Maximum (LGM) (21,000 cal. BP), using existing data for input and validation of the results. The simulations form the basis for a study of the spatio-temporal distribution of Neanderthals during their final thirty millennia, and also of the earliest European anatomically-modern humans. A summary of this study will be presented here.
The archaeology database (comprising ca.1900
age determinations for the period 60,000-20,000 BP) was constructed by William Davies for
testing against the model climate output. The
crucial variables, for the purposes of this paper, are the geographical (latitude and
longitude) and chronological (absolute age determinations) positions of assemblages
attributed to particular archaeological industries. It
was essential to convert 14C determinations to calendar years in order to
render them comparable to results from other absolute radiometric techniques, and the
calibrated ages obtained by the use of the CalPal (Weninger & Jöris 2000) programme
were used for our analyses. For the purpose
of large-scale comparisons, and also owing to the comparatively coarse resolution of the
mesoscale model output (a grid of 60x60 km points across Europe), we have given especial
emphasis to pan-European archaeological entities (Mousterian, Aurignacian and Gravettian)
in the analyses of this paper.
An interdisciplinary project raises many possibilities for the treatment of the archaeological spatio-temporal data which we have collected. Humans can be treated as part of the wider European faunal spatial and temporal patternings, and this issue will be considered briefly. However, the main thrust of the paper will be to consider the human responses to climatic and environmental conditions: what can we as archaeologists say about hominid preferences and tolerances. It must be remembered that analysis of climatic/environmental tolerances and preferences should not be used in a proscriptive sense, imposing arbitrary tolerance thresholds upon Stage 3 hominids, as we can be certain that we cannot use those of current human groups as analogues.
The climatic output variables used in
this paper for comparison with the spatio-temporal distribution of archaeological
assemblages (used as proxies for human presence) are: air temperatures (both winter and
summer), wind-chill (winter), snow depth and snow-cover days per annum. Taking the patterning of the collected data on its
own terms, the Gravettian technocomplex seems to reflect a more developed level of
climatic/environmental preferences and tolerances than hitherto seen for the Mousterian
and [early] Aurignacian. In the context of
deteriorating climatic conditions after 40,000 cal. BP (down to the LGM at 21,000 cal.
BP), Gravettian populations do not appear to show territorial retrenchment
(“nucleation”): no real decrease in the geographical extent of the Gravettian
(in comparison to the Aurignacian) can be discerned.
No doubt the increased complexity of material culture and of landscape occupation
patterns in certain areas (notably in eastern Europe and on the Russian Plain) can be used
to explain the consistent success of the Gravettian.
While none of these observations are novel in themselves, the mesoscale climatic
output of the Stage Three Project allows us for the first time to attempt
continental-scale analyses and comparisons of human responses to environmental changes.
While it proved impossibly
time-consuming to develop a dynamic model for diachronic changes in climate during OIS-3,
the concentration upon reliable models for characteristic “warm” and
“cold” conditions instead allowed us to adopt a more pragmatic approach to the
spatio-temporal patterning in the archaeological data, dividing OIS-3 into four main
climatic stages:
It is evident from the Greenland
ice-core data (GISP2) that the cold troughs seen after 40,000 cal. BP are of equivalent
intensity, if not longevity, to that seen during the LGM itself. It is pointless to try to develop dynamic climate
models for comparison with the temporal pattering of the contemporary archaeology in
Europe, as their fine-grained climatic oscillations cannot be matched by the
coarser-grained fluctuations seen in the frequencies of archaeological absolute age
determinations.
Notwithstanding the light which our
analyses throw upon the perpetual issues of dating precision and accuracy, the model
output can also help us to frame new questions, encouraging us to return afresh to the
original archaeological data. Foremost among
such questions is seasonality: the Russian Plain, for instance, shows great seasonal
variation in temperature, particularly towards the LGM, having cold winters (-17.5 °C; -30 °C with wind-chill) and relatively
warm summers (reaching 18 °C).
The question of whether occupations of the Russian Plain occurred mostly in
summer and autumn we leave to others more familiar with the data. If no such seasonal patterning can be seen for the
Russian Plain, it should serve to remind us that we cannot expect to impose arbitrary
tolerance thresholds on past human populations.
Small-Game Use, the Broad Spectrum
Revolution, and Paleolithic Demography on the North and Eastern Mediterranean Rims
Mary Stiner,
Department of Anthropology, University of Arizona, United States of America.
-------------------------------
Zooarchaeological data on small game
use during the Middle and Late Pleistocene reveal human demographic pulses in some regions
and periods: earliest in the eastern Mediterranean basin and dating either to the
late Mousterian or earliest Upper Paleolithic there; considerably later in southern Turkey
and Italy. Ranking small animal resources according to predator defense strategies
that affect their accessability to humans with and without special tools exposes clear
trends in resource intensification in the form of more even use of high and low ranked
types, and thus increase in dietary breadth. Quick-flight lagomorphs and game birds
initially were low ranked because of their high cost of capture, advantages later reduced
with the evolution of technological aids such as nets, snares, and traps. A secondary
advantage of increased dependence on lagomorphs and game birds is the great resilience of
these populations under conditions of heavy exploitation, in contrast to the situation for
some slow-moving and easily collected animals such as tortoises.
New evidence on the chronology and climatic framework of the Middle-Upper Paleolithic transition
Maria Fernanda. Sanchèz Goni, UMR 5805 CNRS EPOC, Département de Géologie et
Océanographie, Université Bordeaux I, Avenue des Facultés, 33405 Talence, France.
Francesco d’Errico UMR 5808 du
CNRS, Institut de Préhistoire et de Géologie du Quaternaire, Avenue des Facultés, 33405
Talence, France.
---------------------------------
Did climate play a role in the extinction of Neandertals in Europe ? A number of scenarios for the Middle/Upper Paleolithic transition (for ex. papers by Leroyer & Leroi-Gourhan; Hublin; Finlayson et al.; Straus; Zilhão; Demars & Boquet-Appel) consider the replacement of Neandertals by Anatomically Modern Humans (AMH) being in some way climatically or ecologically driven. At the time of a climatic shift, Neandertals would have found difficult to compete with better adapted AMH groups arriving in Europe and were, according to the chosen scenario, rapidly replaced by them, culturally and/or biologically assimilated or temporarily relegated, before their final extinction, to marginal regions. For some authors these regions correspond to areas where Neandertal subsistence strategies were not significantly affected by the climatic change and neandertal groups were, for this reason, able to keep their territories and preserve their way of life for a while. These regions might also be those where AMH could not express at their best the behavioural features which would have guaranteed their success elsewhere. For other authors Neandertal territories were progressively fragmented by the arrival of modern populations and Neandertals pushed towards inhospitable area, which would have eventually accelerated their inevitable extinction.
However, chronological and archaeological evidence to test these hypotheses is ambigous (see discussion in d’Errico et al. 1997; Zilhao & d’Errico 1999) and paleoclimatic data are for several key areas as the Iberian peninsula still rather scant (Sanchez Goni et al. 2000; Van Andel et al. 2000). In particular a more detailed palaeoecological framework is needed to establish whether the so called Ebro Frontier identified by several authors on archaeological and chronological grounds, corresponds to a biogeographical boundary during the OIS3. If so, this might be a strong argument to consider Neandertal and AMH adaptation to different environements as one of the reasons for the geographical divide between these two populations.
To test this hypothesis we need to compare well dated high-resolution palaeoecological data from both regions and correlate them with the archaeological record for the transition.
Palaeoecological evidence for the north of the Iberian peninsula is limited to pollen analyses from archaeological sites (Lezetxiki, Labeko, Otero, Morin, Valina, Romani, Arbreda,) which provide, with the only possible exception of Romani, fragmentary, ill-dated, low resolution records. The unique non-anthropic continuous sequence, the Bañoles lake, only covers the end of OIS3 (from 28 Kyr BP to the present). In the south of the peninsula, the pollen sequence from the Padul peat bog has a low resolution and must be considered of incertain chronology for the period at hand. The pollen analyses from the Carihuela, Beneito, and Perneras archaeological sites have the same drawbacks described above for those in the north.
Here we present two
palaeoclimatic sequences obtained from two IMAGES I deep sea cores retrieved off the
southwestern margin of the Iberian Peninsula (MD95-2042) and in the Alboran sea
(MD95-2043). The main interest of these sequences consists in that they are characterised
by a high sedimentation rate (9 m for OIS3) and provide a continous paleoclimatic record
for OIS 6 to OIS 1 and OIS 4 to OIS 1 respectively. Because of their location close to the
continent they associate high pollen concentration to the full range of marine climatic
proxies (foramininifera, dinocysts, IRD, alcenones, plantonic isotopes). The chronology of
core MD95-2043 is based on a combination of 21 calibrated 14C AMS dates and
isotopic stratigraphy. That of MD95-2042 is established on isotopic stratigraphy and
the identification of Heinrich events. The floristic diversity and richness of the pollen
spectra as well as the occurrence of pollen from the main plant-climatic indicators permit
the application of the transfert function technique (Guiot et al 1998) to both cores. This
allows tentative reconstruction of annual precipitations and winter temperatures for the
Atlantic and Mediterranean sides of the Iberian peninsula during OIS3.
High resolution palynological analysis identifies in both cores 19-20 climatic phases consisting of an alternation of cold/dry and mild/wet periods each lasting for between 500 to 2,000 years which correspond to the Dansgaard-Oeschger oscillations identified in Greenland ice cores. The cold/dry phases result in the development of steppic formation dominated by Artemisia, Chenopodiacae and Ephedra. Annual precipitation are estimated 400 mm below present values for the two areas and winter temperature range between 6 and 10 degrees below present figures. Temperate phases are characterised by open decidous and evergreen forests associated to Pinus. During these phases precipitations and winter temperatures are similar to the present.
The main difference detected in the pollen diagrams between the Atlantic and the Mediterranean sides of Iberia concerns the proportion of plants characteristic of different ecological groups. Ericaceae (heather) are better represented in the Atlantic side while steppic and mediterranean plants show higher percentages in Mediterranean regions. This clearly indicates that cold phases result in a strong dryness of the South Eastern Iberia.
Another main difference appears between the Heinrich events and the other Dansgaard-Oeschger cold events. The former are colder and drier and result in even more widespread steppic formations.
The correlation between the climatic record and the archaeological data is made difficult by the limits of radiometric dating for the period discussed here and by the lack of a reliable calibration curve for 14C dates older than 25 Kya BP. To circumvent this problem we created an uncalibrated age model for MD95-2042 based on the identification of the Heinrich events, which are 14C dated in a number of North Atlantic marine cores.
If we accept that the earliest diagnostic Aurignacian appeared in Western Europe at around 36 kyr BP, our data would place this event at the end of a temperate period (the Is9-10 interstadials) while and that the main developement of this technocomplex would coincide with the very cold Heinrich 4 event and the following temperate Is8 interstadial. In the Iberian peninsula the transition would span five, possibly six, different cold and temperate climatic phases. The implications of this observation for our view of the transition are many. Whatever chronological scale is considered for the arrival of the Aurignacian in western Europe, the duration of this event overlaps several climatic oscillations. Thus climate cannot be considered the main reason for Neandertal extinction and the driving force controlling the colonisation of Europe by AMH.
This research is funded by the CNRS ECLIPSE and OHLL programs.
M.-F. Sanchez Goni acknowledges the Quaternary Research Association for providing the
conference fund to attend the Gibraltar conference
Evolutionary geography of Late Pleistocene Hominins: the
ecology of multiple dispersals
Robert Foley, Marta Mirazón Lahr and
Cara Wall
Leverhulme Centre for Human
Evolutionary Studies, Department of Biological Anthropology, University of Cambridge,
Downing Street, Cambridge, CB2 3DZ, UK
------------------
Recent research has shown that that the colonisation of Eurasia by African hominins was not a single event, but is better described as a series of multiple dispersals (Lahr & Foley 1994). This is the case not just for the earliest colonisation in the Lower Pleistocene versus the spread of modern humans (Out of Africa 1 and 2), but for the discrimination of events within each of these. Archaeological, fossil and genetic evidence shows that there is considerable variation across Europe in terms of both the timing of hominin presence, and also its continuity and duration. Overall, it is apparent that early prehistory of Eurasia is one that involves dispersals, isolation, and extinction, rather than the steady growth of a human presence.
The key
question that arises from this is whether it is possible to understand the pattern of
dispersals into Eurasia – and their evolutionary outcomes - in the light of what is
known about evolutionary processes and ecological conditions (Foley 1989).
In this paper we consider a number of
issues that arise from this proposition. First, we consider the role of dispersals within
the evolutionary process, and develop a model of how dispersals relate to the evolutionary
processes of speciation and extinction, and how these might be related to climatic change
(Lahr & Foley 1998).
This will form the basis for
considering how the specific patterns of biogeographic change in Africa and Europe may
have shaped the pattern of human population structure and differentiation in the Middle
Pleistocene. From this we will then develop a model of the pattern of Eurasian dispersals
and extinction/isolation in relation to the patterns of later Pleistocene climatic change.
These models have implications for the
evolution and isolation of the Neanderthals. These relate primarily to the question of a
recent common ancestor for modern humans and Neanderthals, represented by Homo helmei, and
demographic changes within and between later Pleistocene hominin populations (Foley &
Lahr 1997, in press).
In this context the behavioural and
technological records, specifically the role of Mode 3 technologies, can be used to
elucidate both the evolutionary relationships between the populations, and to consider the
nature of adaptive homoplasies in later human evolution.
The conclusions we draw are that the
settlement of Europe by African hominins during the Pleistocene has been dynamic and
demographically unstable, with repeated colonisations and extinctions. Underlying this
pattern is the way in which the environments of Europe have determined the potential for
long term survival, and we will consider some of the ecological variables that are likely
to have shaped the probability of successful maintenance of hominin populations in Europe
across glacial-interglacial cycles.
Foley R. A. 1989: The Ecological
Conditions of Speciation: A Comparative Approach to the Origins of Anatomically Modern
Humans. In Mellars P., Stringer C.B. (eds), The Human Revolution. Edinburgh, Edinburgh
University Press, 298-320.
Foley R. A., Lahr M. M. 1997: Mode 3
Technologies and the Evolution of Modern Humans. Cambridge Archaeological Journal 7:3-36.
Lahr M. M., Foley R. A. 1994: Multiple
Dispersals and Modern Human Origins. Evolutionary Anthropology 3:48-60.
Lahr M. M., Foley R. A. 1998: Towards a Theory of Modern Human Origins: Geography, Demography, and Diversity in Recent Human Evolution. Yearbook of Physical Anthropology, Vol 41 - 1998 41:137-176.
Faunal remains from the Gibraltar
Caves: amphibians and reptiles in a Late Pleistocene
refugium
Chris Gleed-Owen, 16a Suffolk Avenue,
Shirley, Southampton, SO15 5EG, United Kingdom
-------------------------------
The remains of amphibians and reptiles (herpetofauna) are among the most abundant of the finds gathered from the excavations in Gorham’s and Vanguard Caves on Gibraltar. The diversity of species makes these some of Europe’s most important faunal assemblages from any Quaternary site, let alone one dating largely from a glacial period.
The southern edge of Iberia was
almost certainly the refugium for a large proportion of western Europe’s
thermophiles, but we know little about how glacial refugia worked. The Gibraltar sites
provide a unique insight into the dynamics of a refugium at work. Many of the amphibian
and reptile species identified could not tolerate a severe climatic deterioration,
particularly with respect to summer temperatures. This carries implications for climatic
reconstructions. Changes in faunal make-up and species diversity in the Gibraltar
assemblages between OIS 5a/b (Vanguard Cave) and OIS 3 (Gorham’s Cave) probably
reflect climatic changes. Yet all of the fossil species are present in Iberia today, so
even if Gibraltar was inhospitable to certain species at any time, they must have survived
somewhere else in Iberia (southern Portugal?). Could an oceanic influence have maintained
such a high temperature gradient that summer temperatures on the coastal plain were only
depressed by a few degrees below today’s temperatures?
Another interesting aspect of the
herpetofaunal remains is the use of tortoises (and perhaps lizards and toads) as a food
resource by the Neanderthal inhabitants of Gorham’s. Amphibians and tortoises would
have presented easy, slow-moving targets to human predators. However, as they would
probably have had population boom and bust years governed by environmental factors, their
reliability as a food resource is questionable.
Most of the herpetofaunal fossils
from Gibraltar have yet to be studied, and these are only preliminary findings.
Reference:
Gleed-Owen, C.P. 2001. A preliminary
note on the Late Pleistocene amphibians and reptiles from Gorham’s Cave and Vanguard
Cave, Gibraltar. Herpetological Journal, in
press.