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pending on prevailing conditions, the two systems functioned in the same area.
The situation was probably similar in the Middle East where Moderns and
Neanderthals would have been within the same geographical area for over 60
thousand years (Tchernov, 1992, 1998; Bar-Yosef, 1994, 1998) and in other
Modern Human colonisation and Neanderthal extinction 153

zones of heterogeneous landscapes such as along the edge of the Russian Plain
(Soffer, 1994). Away from these contact zones one or other form would have
been distributed over large areas with minimal contact. These data are in keeping
with theoretical predictions that show that environmental heterogeneity effec-
tively supports long-term coexistence of very similar species (Hanski, 1983;
Taneyhill, 2000).
A case within recorded history illustrates how two human forms (contem-
porary sapiens) coexisted in a geographical area and how one became extinct
subsequently as the direct result of climate change. The work in Greenland
(Barlow et al., 1998; Buckland et al., 1998) recreates a scenario that indicates
that only one of two (Norsemen and Inuits) existing modern human groups
survived the medieval ˜Little Ice Age™. Although the Norsemen had been the
earlier colonisers and were apparently well-adapted to their environment, they
failed to survive a period of extended cold. In contrast, however, available evi-
dence points to there being suf¬cient, if not abundant, resources for the Inuits
at a time when the Viking settlers were having to slaughter their animals for
food. This points to signi¬cant lifestyle differences between the farming, rela-
tively sedentary, Norsemen and the nomadic and wide-ranging Inuits as being
one, if not the main, factor in determining the survival of these groups. There
is no evidence of direct competition nor is it suggested as a possible factor in
the ˜extinction™ of the Norsemen. These two forms behaved as ecotypes and
the analogy with the Modern“Neanderthal situation in the late Pleistocene is
evident. There are other excellent examples that show the effects of climatic
and environmental changes on recent human populations (Binford et al., 1997;
Cachel, 1997; Park, 1998; Sterling, 1999; Verschuren et al., 2000; deMenocal,
2001; Anderson, 2002; Axtell et al., 2002; Weber et al., 2002; Weiss, 2002)
that serve to illustrate that population expansions, crashes and extinctions have
continued to occur in humans independently of competitive processes even into
historical times.
A popular thesis is that competition from the newly arrived and ˜superior™
Moderns caused the extinction of the Neanderthals. The only basis for the
argument is that of an apparent association between the arrival of the Moderns
into Europe and the extinction of the Neanderthals. Inter-speci¬c (or inter-
population) competition is a very dif¬cult phenomenon to demonstrate in any
extant wild population today. For the conditions of competition to apply the
competing populations must be at environmental carrying capacity and must
use similar resources and obtain them at the same times and in a similar enough
manner to make one population™s rate of increase have an effect on the other™s.
If the populations are not at carrying capacity then a situation of resource
superabundance exists and there is no competition.
It is practically impossible to know whether or not Neanderthals and Moderns
were in competition. I suggested, in Chapter 5, that the two forms differed in
154 Neanderthals and Modern Humans

landscape use. This would explain how, in the Middle East for example, Nean-
derthals and Moderns could have co-existed within the same geographical area
over protracted periods. Furthermore, the variability of resources as a result of
climatic oscillations is unlikely to have led to a stable situation that permitted
the two forms to reach carrying capacity and equilibrium populations within the
same geographical area. Coexistence therefore was no more than ¬‚uctuating
levels of two populations below carrying capacity, each with a particular mech-
anism of use of space evolved in different landscapes and geographical areas.
In terms of competitive ability, one could suggest that in a situation of an
expanding population of Moderns and a stable (or even locally growing dur-
ing cool periods when the range boundary shifted southwards) population of
Neanderthals in the Middle East, the likelihood would be that the resident pop-
ulation (in this case the Neanderthals) ought to have a competitive edge over
the pioneers. Knowledge of the territory, its resources and mechanisms of op-
timal resource collection would weigh heavily in their favour. An expanding
population of pioneers would only succeed if it behaved in a different manner
and the conditions favourable for the resident changed. This is what seems to
have occurred in the Middle East. For a long time the two forms occupied the
same geographical area. For much of this time the Neanderthals were proba-
bly on well-established territories and the Moderns would have occupied areas
marginal to the Neanderthals. This would have been particularly likely in areas
like the Middle East with a heterogeneous mosaic of habitats from mountains to
lowland plains and desert. Wang et al. (2000) have shown that two ecologically
identical species can coexist when there is a trade-off between local competi-
tive ability and invasion ability. If we take the view that I take in this book that
the Neanderthals were probably locally competitively superior to Moderns, but
Moderns had greater dispersal capacities, then we have here a theoretical basis
for long periods of geographical coexistence in spite of ecological similarity
(Chapter 5). There would have been a shifting balance between the two pop-
ulations, a kind of semi-permanent geographical coexistence. The population
of Moderns would have expanded when its favoured habitats expanded and
its range slowly penetrated the mountains to the north that acted as a physical
barrier to dispersal. On reaching the plains of Eurasia the limits on this popula-
tion were removed and there was a rapid ecological release and expansion. The
colonisation of the Eurasian Plain, free from physical barriers, rich in resources
and largely free of Neanderthals had to be rapid, and it was.
If the Moderns arriving in Europe from the east had been responsible for the
Neanderthal extinction, then we would expect an east“west pattern of extinction
as the Moderns arrived. Instead we observe a pattern of extinction that is related
to bioclimatic zones strongly suggesting that a climate-driven impact was re-
sponsible (Figure 7.2). I do not, therefore, consider competition from Moderns
Modern Human colonisation and Neanderthal extinction 155




Figure 7.2. Location of late (N, post-35 kyr) Neanderthal sites in relation to
bioclimate. Grey, Mediterranean. Bioclimates after Rivas-Mart´nez (1996). Bioclimate
±
boundaries as in Figure 5.3.



to have been a signi¬cant cause of the extinction of the Neanderthals. This is
probably also so in the case of other archaic forms. If there was competition, it
is likely to have been highly localised and would in all likelihood have favoured
the well-established local populations. Colonisers would only have succeeded
in situations where local groups were in a phase of recession, such as occurred
in south-west France around 40“35 kyr.



Hybridisation

An ecotype is a genetically distinct form that occurs in a speci¬c habitat but
which interbreeds more or less freely with another form that occurs in an ad-
jacent habitat (Cain, 1971). There are many intermediate forms in nature be-
tween ecotypes and good species that exclude each other in different habitats
but with contiguity and no hybridisation. In some cases the observed hybridis-
ation is secondary (Mayr, 1963; Cain, 1971), that is when two forms that differ
156 Neanderthals and Modern Humans

signi¬cantly in their genetic makeup meet comparatively recently in the wild
and a range of hybrids is possible. Cain (1971) considers that most geograph-
ical subspecies should probably be considered ecotypes with a single area of
occurrence and I consider that this terminology is one that is appropriate to the
Modern Human/Neanderthal situation in areas of recent contact.
When hybridisation is too small to be signi¬cant in determining species
limits and when it is so high that the hybridising forms should be regarded as
having combined to form a new species is unclear (Cain, 1971). In particularly
heterogeneous geographical areas such as Iberia, a mix of levels of interaction is
far more likely (see Transition below). Regions of high overlap would occupy
only a small proportion of the geographical area. On current evidence I do
not consider that there was any signi¬cant, large-scale, hybridisation between
Moderns and Neanderthals.
When populations expanding from glacial refugia met they often formed
hybrid zones (Barton & Hewitt, 1985; Hewitt, 1996, 1999, 2000). The main
ones in Europe are centred in the Alps and central Europe as well as the northern
Balkans and the Pyrenees. Such boundaries tend to be narrow, tension, zones
and are marked by a reduction of hybrid ¬tness, the extent of which determines
the zones™ width. Until climate changes a situation some hybrid zones may
become ˜trapped™ in local areas of low density or dispersal. These hybrid zones
may additionally act to protect the integrity of the genomes on either side until
a subsequent glaciation reduces the two to separate refugia (Hewitt, 1996). In
the case of the expanding population of Moderns and the receding population
of Neanderthals in late OIS 3 Europe we may expect that, given the rapidity
of climate change, any existing hybrid zones between the two forms would
not have been stable and would either move, in this case in a north-east to
south-west manner, or disintegrate (e.g. Carney et al., 2000). Recent work
has shown that such movement of hybrid zones, in response to environmental
perturbation (Bynum, 2002), may be important in biogeography and evolution
(Dasmahapatra et al., 2002). Finally, we should not overlook the possibility of
hybrid zones existing between Neanderthal populations as these recolonised
areas of the Eurasian Plain from Iberian and Balkan refugia.
Human populations would have been repeatedly isolated from each other
(Finlayson, 2003). The surviving populations would have re-met during peri-
ods of population expansion. The degree of inter-breeding would have varied
from total inter-mixing to complete isolation. The probability of two human
populations inter-breeding when coming into contact would have depended on
the degree of genetic distinctness of each population which, in turn, would have
been dependent on the degree of prior isolation. The question of inter-breeding
of previously isolated populations would not just have affected the Moderns
and Neanderthals, which is the case that is receiving greatest attention today
Modern Human colonisation and Neanderthal extinction 157

(Chapter 4; Duarte et al., 1999; Tattersall & Schwarz, 1999), but different
Neanderthal populations that had been isolated in different refugia. Similarly
the degree of inter-breeding between Moderns and Neanderthals may have var-
ied between regional and local populations of each. On current genetic evidence
we can conclude that there was no long-term Neanderthal genetic contribution
to the present-day human gene pool (Chapter 4). It is impossible, on present evi-
dence, to assess the degree of inter-breeding and the contribution of Neanderthal
and early Upper Palaeolithic Modern genes to each other™s populations.
I therefore predict that human range expansions and contractions were fre-
quent and of varying extent, only the most widespread and intense being
recorded in the fossil and archaeological record. There would have been spatio-
temporal variability in the degree of secondary hybridisation and contact be-
tween populations that became allopatric during glacial events (Cain, 1971).
Behavioural, morphological and physiological isolating mechanisms, when
present, would have acted to maintain population distinctness.


Behavioural differences and cultural exchange

The cognitive abilities of the various populations of the sapiens polytypic
species (that included Neanderthals and Moderns) would appear to have a
common and distant origin and the taxonomic de¬nition of human popula-
tions is arbitrary (Chapter 4). The human lineage may be regarded as a single
palaeospecies with geographical populations of varying degrees of distinctive-
ness at any particular point in time. Thus for any time period it should be produc-
tive to consider global human populations as forming a polytypic species com-
plex (Chapter 4). Evidence from Africa in particular indicates that behaviour
attributed to ˜modernity™ as part of the European Upper Palaeolithic Revolution
has much earlier origins (Chapter 5). Behaviour, including social behaviour,
culture and technology, would have evolved as adaptive responses to speci¬c
situations. Responses to similar environmental and social pressures would have
been met by similar, though not necessarily the same, solutions. Cases, such as
the development of so-called ˜Upper Palaeolithic™ or ˜transitional™ technologies,
should be seen from the perspective of behavioural convergence. This should
nevertheless not negate the possibility of cultural and technological information
exchange where different groups met and interacted. As with other biological
aspects dealt with in this book, a mosaic of possibilities would have existed and
it is unrealistic to seek a common solution.
The question of acculturation or the independent evolution of cultural at-
tributes is of considerable controversy today, particularly in the context of the
arrival of the Aurignacian in Europe and the emergence of Middle Palaeolithic
158 Neanderthals and Modern Humans




Figure 7.3. Distribution of ˜transitional™ industries in relation to bioclimate.
C, Chatelperronian; U, Uluzzian; A, Altmuhlian; S, Szeletian; J, Jerzmanian;
L, Lincombian. Bioclimates after Rivas-Mart´nez (1996). Bioclimate boundaries as in
±
Figure 5.3. Transitional industries after Raposo (2000).



technologies with Upper Palaeolithic elements (d™Errico et al., 1998; Mellars,
1999; Zilhao & d™Errico, 1999). I view this as a problem of contact and I am of
the view that contact in the case of Moderns and Neanderthals in Europe was
restricted on account of low population sizes and habitat differences. We have
also seen the degree of ¬‚uidity in the adoption of Middle or Upper Palaeolithic
(or Middle Stone Age/Late Stone Age) technology in response to environmental
change, both in Moderns and Neanderthals (Chapter 5). In a cooling world in
which the Neanderthal populations were being forced into refugia, it could be
expected that technological changes that favoured existence in marginal zones
would be favoured. The presence of the intermediate technologies occurs pre-
cisely in such intermediate areas between the heterogeneous zones of Europe
and the plains and clearly they must be adaptations to a changing resource and
habitat structure world (Figure 7.3). Given the degree of ¬‚exibility between the
types of technology adopted by Moderns and Archaics across the world it is
Modern Human colonisation and Neanderthal extinction 159

not unreasonable to expect behavioural responses such as those documented in
Europe to evolve repeatedly in isolated populations. For example, in the late
Middle Palaeolithic population of the Nile there were two populations: those
with a new material culture from the south; and those that developed a local
complex that evolved and was therefore not replaced by technological change.
In north-east Africa the transition was independent in the two groups and after
a long period of coexistence. It may have happened in the context of enhanced
social interaction and probably because of it (Van Peer, 1998). The degree of
coincidence with the arrival of Moderns does leave the door open in respect
of whether such behaviours arose independently or whether, instead, they were
obtained by copying (acculturation). In north-east Asia the early presence of the
Upper Palaeolithic, around 42 kyr, is characterised by blade production, with
the retention of Levallois cores, but the retention of Mousterian technology as
late as 35“28 kyr (Brantingham et al., 2001) is a further indication of the func-
tionally adaptive nature of these industries and of the duration of the transition,
especially in zones of contact between the plains and the heterogeneous belt.
Interestingly, early Upper Palaeolithic blade technology is associated with open
air sites but its geographical distribution remains largely in the heterogeneous
environments south of 55—¦ N. It is with the opening of areas to the north, that
were covered by boreal forest and were replaced by mammoth-steppe, after
30 kyr that we observe the typical Modern Human pattern of plains exploitation
(Goebel, 1999). These examples illustrate the complex interactions between
Moderns, Neanderthals and their adaptation to changing environments. In eco-
tonal areas where the plains met the mid-latitude belt, such as in southern
Siberia, we observe the degree of experimenting that led to the invention of
new ways of exploiting the changing environments.
The nature of the landscape would have been largely responsible, at any stage,
for the adaptive behavioural ecology characteristics of each human population.
It is expected that human populations selected regions, landscapes and habitats
that maximised their ¬tness. Areas high in biomass or in diversity would have
been the prime focus. In the ¬rst case the open savannahs of Africa and the
great plains of Eurasia would have been particularly favourable. In the second
case ecotones, zones with a number of distinct habitats over a small area, would
have been optimal. Ecotones would have included coastal areas, lake margins,
riverside habitats and topographically heterogeneous zones. In the latter case

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