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I will con¬ne my discussion largely to the Eurasian and African land masses
which is where the main events took place.


Vegetation structure

In this book I will place particular emphasis on vegetation structure, that is the
three-dimensional arrangement of plants in space. The reason for this is that I
consider that vegetation structure will have played a major role in the distribution
of humans, as it does for most animals (Bell et al., 1991). Vegetation structure
would have been particularly important in determining the types of potential
prey available to humans and also in making prey visible and accessible. Part of
the reason why forests were among the last habitats to be colonised by humans
(Gamble, 1993) must have had to do with prey visibility and accessibility as
well as density.
We may describe vegetation structure according to the distribution of plants
on the ground layer (forbs and grasses), the shrub layer and the tree layer (Kent &
Coker, 1992). Even though the species composition will vary signi¬cantly be-
tween regions of the world, vegetation structure shows similarities. For the
purpose of this book I will cluster habitats by vegetation structure into the
following blocks.




9
10 Neanderthals and Modern Humans

Forests

There is a predominance of trees at high density with a dense canopy. Variants
include tropical and equatorial rainforests, where the canopy is very high, and
temperate broad-leaved forests.


Shrublands

There is a predominance of shrubs with the virtual absence of trees. Today,
characteristic examples are the Mediterranean shrublands, known by speci¬c
names in different parts of the world (e.g. matorral, chaparral; Cody, 1974).


Open habitats

These are characterised by the absence (or presence in low density as in wooded
savannah) of trees and shrubs and a predominance of grasses, forbs, mosses or
lichens, or by the total absence of vegetation in patches. Savannahs, steppe and
tundra cluster under this de¬nition.


Deserts

Deserts occupy large areas of the planet and are characterised by the virtual
absence of vegetation on account of low and irregular rainfall (Cox & Moore,
1985). There are sandy, rocky and ice deserts. Deserts are therefore a separate
category of habitat that cannot be described adequately by vegetation structure
other than as extreme open habitats. For the purpose of this book I will consider
deserts to be a separate category. In human terms deserts have played a major role
as barriers to dispersal. Human adaptations to deserts are extreme developments
of adaptations to open habitats.


Rocky habitats

These are areas with a minimal vegetation development and a preponderance
of a rocky substrate that, like deserts, may be considered extreme cases of open
habitats. Unlike deserts they are usually localised at the landscape and regional
scales. Two types of rocky habitats have been particularly important to humans.
Where the inclination of the land is vertical, or nearly so, rocky habitats are
described as cliffs. Cliffs have attracted humans as areas for shelter or where
Biogeographical patterns 11

specialised fauna (e.g. ibexes Capra spp.) are concentrated. Within rocky areas,
especially in karstic environments, are cavities. These have been traditionally
used by humans as shelters.


Wetlands

Lakes, marshes, alluvial plains, rivers and estuaries and deltas are special habi-
tats. They are usually localised on a regional scale. Their main characteristic is
the presence of standing water (usually fresh or brackish). Margins will often
be vegetated with grasses, reeds and shrubs. Wetlands, depending on climate,
may be seasonal. They attract concentrations of animals at speci¬c times of
the year and are additionally sources of animals not found in other habitats,
especially ¬sh. Wetlands have been extremely important to humans throughout
the Quaternary (Nicholas, 1998).


The sea

Human exploitation of the open ocean is a recent phenomenon (Gamble, 1993;
Fern´ ndez-Armesto, 2000). The products of the sea have, however, been ex-
a
ploited by humans in coastal areas since, at least, the last interglacial (Balter,
2001). Like deserts, the sea has often played a major role as a barrier to human
dispersal even though this has not always been the case, the colonisation of
Australia before 50 kyr ago being a case in point (Thorne et al., 1999; Bowler
et al., 2003).


Mosaics: transitional and edge habitats and
heterogeneous landscapes

The habitat categories that I have so far described will be those that I will
be using throughout this book. They are habitats from the human perspective.
Where these habitats meet there may be sharp discontinuities between one and
the other. These edge areas or ecotones are areas of high diversity (Kerr &
Packer, 1997). These could occur, for example, where wetland and forest come
into contact or where plains or cliffs come into contact with the sea in coastal
areas or indeed where forest and open habitats are close to each other.
After a perturbation an area may experience a succession of habitats over
a period of time (Bazzaz, 1996). The classic example is the regeneration of
woodland after a ¬re. Depending on the point in time at which we look at an
area we may observe it in transition. This is not unusual and it is my contention
12 Neanderthals and Modern Humans

that such transitional situations were the rule at particularly critical stages in
the Quaternary. The abrupt climatic changes that have been recorded at the
scale of decades and centuries with the consequent rapid alterations to the
vegetation (Chapter 6) meant that large areas of the world would have had
transitional habitats for long periods. Given that the climatic peaks occupied a
small proportion of the Quaternary (Lambeck et al., 2002a, b) and that, even
these peaks were often highly variable, we have to accept that large areas of the
planet that were occupied by humans during the Quaternary would have been
dynamic in habitat features at the scale of human generations.
Finally, where spatial discontinuities exist in critical variables at the landscape
or regional scales we ¬nd habitat mosaics rather than uniform blankets of single
habitat (Forman, 1995). Such mosaics are especially common today as humans
continue to modify the environment but they would have always existed. Such
mosaics would, like edge and transitional habitats, have offered opportunities
for humans to exploit the natural diversity within.


Altitude

I do not consider mountains as a speci¬c habitat category in this book. The
habitats described so far may be found at high altitude and their extent would
have varied in most cases in response to climate changes in a similar manner
to latitude (MacArthur, 1984). The highest mountains, however, acted as phys-
ical barriers to human dispersal, especially in the coldest moments when they
were virtually impenetrable. In Eurasia, the Himalayas continue to be a barrier
even today. The belt of mountains stretching from the Iberian Peninsula and the
Maghreb in the west to the Himalayas in the east was critical in human evolution
(Finlayson et al., 2000a). Large changes in altitude over short distances pro-
duced landscape mosaics with high local biodiversity as happens today (Cody,
1986). This was, in my opinion, critical to the evolution of the Neanderthals. In
contrast, the generally low-lying and topographically homogeneous Eurasian
Plain, stretching from Britain to the Bering Strait, was only fully colonised by
humans very late in the Pleistocene (Chapter 7).


Habitat changes in the Quaternary

The climatic oscillations of the Quaternary, through changes in temperature and
rainfall, produced many large-scale changes in the geographical distribution
and the extent of a number of the habitats described above. These changes are
summarised below.
Biogeographical patterns 13

Forests

Tropical and equatorial rainforests contracted their range signi¬cantly dur-
ing arid events that were associated with increasing cold (Lezine et al, 1995;
Colinvaux et al., 1996; Dam et al., 2001) and expanded their range during
wet periods that were associated with warm events. Temperate broad-leaved
forests expanded from their European strongholds eastwards during warm and
wet events and contracted westwards during cold and arid ones (Chapter 6;
Zagwijn, 1992). These forests expanded the northern edge of the range in warm
events reaching as far north as Scandinavia. The northern edge of the range of
these forests contracted in cold and arid events (Chapter 6; Zagwijn, 1992). The
expansion on the southern edge of the range was limited by the Mediterranean
Sea. Boreal coniferous forests shifted their range north and south in response
to warming and cooling (van Andel & Tzedakis, 1996). In the Mediterranean,
montane coniferous forests shifted their range up and down mountains in a
similar manner whereas the thermophillous Mediterranean pines reached their
maximum extent in interglacials (Finlayson, 1999).


Shrublands

Shrublands would have ¬‚uctuated in area as transitional habitats, such as forests,
gave way to open habitats and vice versa. In the Mediterranean Basin, Mediter-
ranean shrubs persisted throughout the Quaternary. Their range would have
contracted at the expense of forest in warm and wet periods and at the expense
of steppe in cold and arid ones (Carri´ n et al., 2000). Shrublands would there-
o
fore have occupied large expanses of the Mediterranean Basin at different times
in the Quaternary. Although their extent has increased as a result of human ac-
tion through deforestation the Mediterranean shrublands would appear to have
a long evolutionary history (Blondel & Aronson, 1999). To the north and south
of the Mediterranean the more extreme boreal and tropical conditions are likely
to have led to more rapid and abrupt changes from forest to open habitats and
back. The intermediate position of the Mediterranean lands would have made
them best suited for the development of shrubland communities and habitats.


Open habitats and deserts

In Africa, savannahs and grasslands expanded at the expense of rainforest during
cold and arid periods and at the expense of desert during warm and wet periods
(Chapter 6; Dupont et al., 2000) and vice versa. The maximum extent of the
14 Neanderthals and Modern Humans




Figure 2.1. Distribution of main habitat and topographic blocks referred to in this
book. MLB: mid-latitude belt.


Sahara would have been reached during most arid moments (Swezey, 2001)
when it would have been a barrier to human dispersal (Marks, 1992; Lahr &
Foley, 1994). In the wettest events, on the other hand, the Sahara was virtually
taken over by grasslands and savannah. During such times its effect as a barrier
to dispersal would have been insigni¬cant. The development of grasslands in
South-east Asia would have followed a similar pattern except that their extent
would never have been as great as in Africa (Dam et al., 2001).
In Eurasia the expansion of steppe westwards occurred during arid events (van
Andel & Tzedakis, 1996). Its western limits receded signi¬cantly during warm
and wet events and the expansion of forest. At their maximum extent, steppes
covered much of the central tablelands (mesetas) of the Iberian Peninsula.
Tundra expanded south and west during glacials. The ice deserts expanded
southwards, reaching their maximum extent during the coldest and wettest
glacials. In the Mediterranean, mountain glaciers responded in a similar manner.



Contrasting equatorial, tropical and sub-tropical Africa, the
intermediate mountainous belt and the northern plains

In terms of habitat and topographical characteristics that would have been sig-
ni¬cant to humans we may divide Africa and Eurasia into three major blocks
(Figure 2.1).
Biogeographical patterns 15

Tropical and sub-tropical Africa

This is essentially the geographical area from within which hominids, including
humans, originated and dispersed. In habitat terms there has been a dynamic
expansion and contraction of rainforest, savannah, grassland and desert through-
out the Quaternary (deMenocal 1995; Dupont et al., 2000; Swezey, 2001). The
reduction in rainforest at the expense of open habitats has been proposed as a
major factor in human evolution (Foley, 1987; Foley & Lee, 1989; Kingston
et al., 1994). The contraction of the Sahara has been proposed as a major factor
permitting the dispersal of tropical African animals, including humans, north-
wards. The combination of plains and heterogeneous landscapes, particularly
along the Rift Valley, would have produced ample opportunities for ecologi-
cal diversi¬cation and allopatric isolation among hominids (O™Brien & Peters,
1999).


The intermediate mountainous belt

This is the belt that stretches from Iberia and the Maghreb in the west to the
Himalayas in the east. Any Eurasian population to the north must have dispersed
from this area. Its southerly position within the Eurasian landmass made this
belt suitable for permanent or semi-permanent human occupation (Finlayson
et al., 2000a). These lands, because of their latitude, would have been less
affected by the severity of the glaciations than the plains immediately to the
north. The west would have been especially suitable on account of the oceanic
in¬‚uence of the Atlantic. This belt therefore provided a number of refugia for
many species, including humans, during the glaciations (Hewitt, 1999).
Different parts of this wide longitudinal area would have offered different
opportunities on account of their characteristics (Finlayson, 2003). The Iberian
Peninsula in the west would have been the major refuge for European human
populations being largest in area of the Mediterranean peninsulas and because
of the milder oceanic climate, especially along its coasts. The interior tablelands
would have experienced more severe climatic situations. The Strait of Gibraltar,
immediately to the south, would have been open throughout the Quaternary so

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