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the need for females to remain in ¬xed locations for extended periods. I interpret
Modern Human“Neanderthal problem 83

these features in the context of the behavioural ecology of the Neanderthals (see
Chapter 5). They are indicative of a form occupying heterogeneous landscapes
with a behaviour pattern that required long and sustained movement and a
close-quarter hunting strategy.
Of the cranial features that typify Neanderthals, the large incisors may be the
easiest to explain. The evidence of high wear in these teeth suggests that they
had a non-masticatory, clamp-type, function (Brace et al., 1981; Smith, 1983;
Trinkaus, 1993). The size and shape of the skull and the brain, reaching higher
volumes than in Moderns (Stringer & Gamble, 1993), has not been satisfactorily
explained although it is now clear that differences between Modern Humans and
Neanderthals arise early in ontogeny (Ponce de Leon & Zollikofer, 2001). Cold
climate explanations, as we will see below, are inadequate. The signi¬cance of
the supra-orbital torus (brow ridge), attributed by some authors as a skeletal
adaptation to localised and intermittent biomechanical stresses (Russell, 1985),
is similarly not satisfactorily understood (Stringer & Gamble, 1993).
The large body mass, breadth of trunk and shortness of the limbs have been
interpreted as adaptations to the cold (Ruff, 1994; Holliday, 1997a, b). Attempts
to contrast lower limb length with climatic and mobility variables among extant
human populations have been based on poor data sets and have been inconclu-
sive (Holliday & Falsetti, 1995). The large nose is also regarded as an adap-
tation to the cold (see below). Body mass is closely correlated with a number
of biological parameters including basal metabolic rate, respiratory and cir-
culatory physiology, locomotion, growth and reproduction, social dominance,
mating success, and size and types of food consumed. In addition phylogenetic
trends are known to correlate with body size at the species level in mammals
(Alroy, 1998). Surface area and metabolic rate are closely linked to body size
so that changes in body size for reasons other than climate can affect changes
in surface:volume ratios (Brown & Gibson, 1983; Peters, 1983). Body size in
mammals is additionally linked with primary productivity (Rosenzweig, 1968),
available prey size (McNab, 1971) and fasting endurance in seasonal environ-
ments (Lindstedt & Boyce, 1985). The dif¬culty of establishing causality is
exacerbated in species that are capable of modifying their environment cultur-
ally. For example, Moderns developing systems of storage would effectively be
reducing seasonality, and the selective pressure for fasting endurance would be
reduced.
The perception of the Neanderthals as cold adapted to the conditions of
glacial Europe is prevalent (Brose & Wolpoff, 1971; Trinkaus, 1981; Gamble,
1993; Stringer & Gamble, 1993). The evidence in support of this notion is, how-
ever, inconclusive. If it is argued that Neanderthals and Moderns were different
species then intra-speci¬c ecogeographical rules (Bergmann™s and Allen™s in
particular) should not be applied (Mayr, 1963; Cain, 1971). Even if the two
84 Neanderthals and Modern Humans

forms are regarded as belonging to the same species the validity of applying
such rules to spatially and temporally separated populations is suspect given
that it would be unreasonable to assume that between different geographical
areas and time periods the only independent and changing variable affecting
morphology was climate. In addition conclusions based on strong assumptions
of uniformitarianism, which rely on analogy with extant organisms, need to be
treated with caution (Van Valkenburgh, 1994). Morphology can determine the
ecological range of the phenotype and may limit ecological and geographical
distribution (Ricklefs & Miles, 1994). The environment also affects morphol-
ogy in a range of ways including physical factors (e.g. climate), habitat and
landscape structure (e.g. via locomotor structures), diet breadth and resource
partitioning (Ricklefs & Miles, 1994). It is therefore very dif¬cult, and even
unrealistic in a multivariate world, to attempt to correlate morphology to a
single variable such as climate (e.g. Dayan et al., 1991) unless all these other
variables are regarded to be constant among the forms being considered and
across the vast stretches of their geographical ranges, which clearly they were
not. The expectation is particularly unrealistic for such highly adaptable forms
as the Neanderthals and Moderns that would not have been restricted to very
speci¬c conditions. To argue for cold adaptation when Neanderthals and their
predecessors survived for tens of thousands of years in the variable climates of
Europe, in which full glacials only took up a small part of the time (Chapter 6),
and predominantly in southerly latitudes (Chpater 7), is illogical.
It could be argued that while such criticism is valid for post-cranial mor-
phological features such as limb proportions, whose characteristics would have
a clear ecological dimension, it might not be for other features, such as nose
shape and size. The large protruding nose of Neanderthals has been considered
to have been an adaptation to extreme cold and arid conditions, its function
being to warm the air entering the lungs (see review in Stringer & Gamble,
1993) although others have suggested that the Neanderthal nose may have been
a means of losing heat generated by a very active life style (Franciscus &
Trinkaus, 1988). Czarnetzki (1995), in studying the Neanderthal nose, on the
other hand, concluded that it must have been adapted to the peripheries of hot,
humid regions, perhaps even subtropical to moderate biotopes. Possible exper-
imental support for a warm climate function comes from studies of selective
brain cooling in mammals (du Boulay et al., 1998). These workers found that
the internal carotid artery blood of macaques was 1“2 —¦ C below the core body
temperature and that selective brain cooling was a major factor constantly at
work in a normal primate. The cooling occurs after the blood leaves the aorta
and is due to the close proximity of the carotid artery to the trachea, larynx
and pharynx. The dominant in¬‚uence on the lowered temperature within the
internal carotid artery in monkeys was apparently the temperature of inspired
Modern Human“Neanderthal problem 85

air. The anatomy is very similar to that of humans and these workers concluded
that a similar mechanism is at work in humans.
Part of the observed neurocranial variation in contemporary Moderns is re-
lated to climate, thermoregulation having a greater effect on the cranium than
upon the body as a whole (Beals et al., 1984). For Neanderthals living in the
warm conditions of mid-latitude Europe, and with presumably an even greater
brain-cooling problem than Moderns on account of their larger brain volume
(e.g. Stringer & Gamble, 1993), a nose with a reduced surface area exposed to
air passing through the nasal cavities (Czarnetzki, 1995) could have acted as
a tool for reducing the warming of inhaled air. This could confer a signi¬cant
advantage to individuals that might have their hours of activity curtailed by
the risk of heat strain (e.g. Ulijaszek, 2001). An air-warming function would
instead increase the brain-cooling problem. As du Boulay et al. (1998) point
out, heavy exercise or a hot and humid atmosphere with the consequent intake
of warm air could further increase brain metabolic rate with the production of
still more heat. The functional morphology of the facial characteristics of Nean-
derthals, with their in¬‚ated cheeks (Stringer & Gamble, 1993), would also seem
to be in need of reassessment since it is apparent that brain cooling in humans
is aided by cooled blood ¬‚owing from the facial skin backwards through the
orbital veins towards the cavernous sinus, which may act as a heat exchanger
(Kratzing & Cross, 1984).
The evidence available therefore runs counter to the notion that Neanderthals
were morphologically and physiologically cold-adapted. Instead, the suppos-
edly warm-adapted Moderns were able to fare better in these cold conditions,
undoubtedly assisted by cultural devices. Some authors have gone to the ex-
treme of regarding the Neanderthal morphology to be ˜hyperarctic™, drawing
analogy with modern Eskimo populations (Ruff, 1994; Holliday, 1997a). Cer-
tainly, the Iberian populations of Neanderthals would never have been exposed
to the climatic extremes of regions presently occupied by these northern peo-
ples. If we analyse the mean annual temperature (T) variation across stations
in a quadrant bound in the north by 70 —¦ N, in the south by 50 —¦ N, in the west
by 150 —¦ E and in the east by 130 —¦ W (covering Alaska, eastern Siberia and ad-
jacent areas) for the period 1950“1990 (Climate Research Unit, University of
East Anglia), we ¬nd that the range of T falls between ’0.28 —¦ C and ’2.23 —¦ C
(mean ’1.33 —¦ C). Comparable data for the Iberian Peninsula gives a range of
16.77 —¦ C to 18.23 —¦ C (mean 17.48 —¦ C). In Iberia, the ecological conditions suit-
able for Neanderthal survival would have disappeared with a decline in T of
between 8 —¦ C and 10 —¦ C (Chapter 7), long before such low Arctic temperatures
would have been reached. These results also put into question the validity of
predictions of the temperatures to which Neanderthals were exposed based on
extrapolations from morphology (Holliday, 1997b). It is similarly unlikely that
86 Neanderthals and Modern Humans

30




20 T-3

T-8

10
Mean Annual Temperature




0

hyper


-10 T-13



-20
30.00 35.00 40.00 45.00 50.00 55.00 60.00

Latitude

Figure 4.1. Estimated effect of drops in mean annual temperature (T) with latitude.
The horizontal ˜hyperarctic™ line corresponds to a present-day T for Alaska and
eastern Siberia. Since ecological conditions necessary for Neanderthal survival would
have disappeared from, for example, Iberia with a drop in T of between 8 and 10 —¦ C
(Chapter 7), it is predicted that Neanderthals would not have experienced ˜hyperarctic™
conditions over the greater part of their geographical range.


Neanderthals further north in Europe would have ever been subjected to such
low values of T, as their habitats would have similarly disappeared before such
extreme temperatures were reached. In Figure 4.1 I show the results of extrap-
olating current T values, in latitude bands of 5 —¦ across a belt of Europe from
10 —¦ W to 10 —¦ E, by depressing T by 3 —¦ C, 8 —¦ C and 13 —¦ C. The latter temperature
would represent the extreme temperature drop at the height of the last glacia-
tion (Dansgaard et al., 1993). The present-day T range for the Alaskan“Siberian
(˜hyperarctic™) quadrant is also included as a reference. It is clear from Figure
4.1 that the T drop at the height of the last glaciation would have produced
values of T comparable to the hyperarctic sample in latitudes north of approx-
imately 45 —¦ . Drops in T more in keeping with prevailing conditions in OIS 3,
when the Neanderthals became extinct, would have produced hyperarctic
Modern Human“Neanderthal problem 87


conditions only further north, above the 55th parallel. It is highly unlikely that
Neanderthals ever lived north of this parallel (approximately the latitude of
Copenhagen, Denmark) and few would have lived north of the 45th parallel
(approximately the latitude of Milan, Italy) in cold episodes. The conclusion
is that Neanderthals would never have been exposed to T values remotely near
those that could be considered hyperarctic. Whether or not Neanderthals had
physiological and morphological characteristics that alleviated existence in cool
and arid climates is not critical to questions of survival.
Cold-adaptation is therefore an inadequate explanation of Neanderthal mor-
phology. Bone robusticity, shape and orientation of joints, and size, and ori-
entation and mechanical leverage of their muscles are most likely to re¬‚ect an
emphasis on strength and endurance required for high mobility, close-contact
hunting with short-range weapons and production of high reaction forces in the
upper limb (Churchill, 1998).
Moderns differed morphologically from Neanderthals in a number of ways.
Obvious differences in cranial shape included a more ¬‚attened, retracted, face
(Lieberman et al., 2002) that may re¬‚ect decreased use of the anterior teeth
(Klein, 1999). Skull shape may also re¬‚ect structural changes in the brain
(Lieberman et al., 2002). We cannot, however, distinguish at present between
possible functional differences in cranial shape between Moderns and Nean-
derthals and differences due to genetic drift in small populations of these ho-
minids. Cranial robusticity is linked to cranial size but not shape. Moderns
from the late Pleistocene to the present have signi¬cant reductions in cranial
dimensions, estimated at 10“30% between Upper Palaeolithic humans and re-
cent Europeans. These changes have not been uniform and there are signi¬cant
regional differences today. The Australian aboriginal pattern, however, bears
no relationship to that of early Upper Palaeolithic hominids and is considered
to re¬‚ect adaptation to Pleistocene Australia over a long period of isolation
after an early entry (Lahr, 1994; Lahr & Wright, 1996). This entry may have
occurred before the complete ¬xation of the mtDNA lineage now found in all
living people (Adcock et al., 2001).
The reduction in post-cranial robusticity and the relatively longer limb pro-
portions in Moderns in all probability re¬‚ect adaptive responses. For reasons
explained with reference to the Neanderthals, bioclimatic explanations are un-
satisfactory. Reduction in robusticity, which continues in the Upper Palaeolithic
and into the Holocene (Frayer, 1984), is probably related to a gradual reduction
in habitual load levels (Trinkaus, 1997) related to the use of projectile technol-
ogy and associated social correlates as well as to the nature of the landscape
being exploited. Long distal limbs would have been particularly advantageous
in the development of long-range mobility strategies over ¬‚at, open, terrain
88 Neanderthals and Modern Humans

(Chapter 5). Pelvic differences with Neanderthals may also re¬‚ect locomotory,
rather than reproductive, differences (Klein, 1999).


Behaviour

Issues of behavioural complexity in middle Palaeolithic humans have come to
the fore in recent years, taking over from the stagnation of fossil and archae-
ological discoveries (Stringer, 2002b). The discovery of 400 kyr-old wooden
spears in Schoningen, Germany (Thieme, 1997), revealed the extent to which
our perception of technological development, which has been based largely on
stone tools, underestimated the capabilities of archaic humans. The possible ex-
istence of Lower and Middle Pleistocene huts and evidence of the early control
of ¬re also point to the very early origin of technology that must have rapidly
widened the niche of Homo (Gamble, 2001).
The links between technology and biology are increasingly diffuse (van Peer,
1998) as it appears that archaic sapiens had the capacity for ˜modern™ behaviour
as re¬‚ected by the use of particular technologies in relation to changing ecol-
ogy (Ronen, 1992; Foley & Lahr, 1997; McBrearty & Brooks, 2000). Technol-
ogy also varied in response to environmental change among Moderns (Blades,
1999). Were changes in technology responsible for human range expansions
or were they a response to new ecological settings? The recent con¬rmation
of the antiquity (c. 50 kyr) of the Lake Mungo 3 (Australia) Modern Human
skeleton (Thorne et al., 1999; Bowler et al., 2003) with evidence of the use
of ochre (considered a modern trait) raises important questions concerning the
geographical and temporal distribution of modern behaviour. These issues are
addressed in detail in Chapter 5.


Patterns

The polarised human origins debate has, in seeking the ultimate solution, damp-
ened the very nature of the mosaic that has been the spatio-temporal pattern
of human evolution in the last two million years in response to the pressures
imposed by climate change. From tropical African origins different forms of
Homo, with different degrees of genetic distinctness, have populated the world
with increasing success. Where populations have met, the outcome has not been
dependent on the populations themselves but, invariably, on external factors.
Whether there was genetic mixing or not would have depended on the degree
of genetic distinctness and the probability of contact. Regional differentiation
and continuity, replacement or colonisation of vacant areas are segments of a
Modern Human“Neanderthal problem 89

continuum. The use of culture as an all embracing and all pervading explana-

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