| |
|
Abstracts |
|
Tectonics
and climate in relationship to human evolution |
| Dr
Mark Maslin |
| Department
of Geography, University College, London |
|
Abstract |
|
Many
believe that environmental change in Eastern Africa stimulated the
evolution of early humans. The two driving forces of environmental change
in this area over the last 10 million years are local tectonics and global
climate change. In this talk I want to examine first the control that
regional or large scale tectonics has on global climate. As much of the
present climate system can be explained by past tectonics. Indeed many of
the climatic transitions which have occurred since the Miocene have been
tectonic in origin, though modulated by changes in the Earth's orbit
around the sun. In the second part of the talk I will examine how the
local tectonic changes in Eastern Africa caused major uplift and rifting.
This altered the landscape of East Africa from a flat rainforest dominate
area to a highly variable landscape with many different types of
vegetation. Indeed the tectonic changes made East Africa much more
sensitive to climate change, may be even producing an environment that
varied throughout single human lifetimes. It is on this dynamic background
that human evolution occurred. Hopefully along the way I can point out
possible links between our evolution and the major tectonic and climate
events.
|
| |
|
Water,
palaeoenvironmental change and hominid evolution in Africa |
| Dr
Eileen O’Brien |
| Institute
of Ecology, University of Georgia, USA |
|
Abstract |
|
Central
to understanding the course of human evolution, is understanding how
Africa's physiography and biota have changed since the Miocene. For the
last several decades the emphasis has been on understanding the impact of
global changes in temperature on Africa's biota-especially on linking
Milankovitch cycles and Pleistocene ice-age cycles to paleoenvironmental
changes in Africa. Indeed, orbital forcing of temperature change has even
been invoked as an evolutionary mechanism. Herein I depart from tradition
and focus on changes in Africa's water supply as the primary impetus for
changes in Africa's climate and biota, and thus hominid paleoecology and
evolution. The keypoints include: a) something other than changes in
insolation drove changes in Africa's biota--except at its highest
elevations and latitudes, Africa receives a 'surplus' of insolation,
making changes in rainfall the major climatic factor limiting Africa's
biota; b) something other than Milankovitch cycles are causing ice-age
cycles since they are now documented back to the Triassic, which makes
them 'normal' earth-sun phenomena and unlikely causes of rare ice-ages; c)
changes in Africa's topographic relief, hydrology and location relative to
Eurasia since the Miocene are more than sufficient explanations for
changes in Africa's climate and biota during the course of hominid
evolution; d) based on empirical analyses of present-day relationships,
the primary effect of changes in the water-energy regime on Africa's biota
would be changes in its distribution-the realized distribution and
diversity of vegetation causing changes in the distribution and diversity
of mammals due to changes in their dietary/shelter resources; and e)
relationships established between climate (water-energy dynamics) and
present-day changes in potential dietary resources, associated vegetation,
and mammal diversity in Africa provide objective models for predicting the
impact of past/future changes in climate (regardless of their cause). They
are also an objective test of inferred paleo-environmental changes based
on the geologic, paleontological and paleobotanic records.
|
| |
|
Species
diversity and climate |
| Professor
Peter Andrews |
| Department
of Palaeontology, The Natural History Museum, London |
|
Abstract |
|
Fossil mammals form the basis for many palaeoecological reconstructions of
hominid sites, the reason being that fossil hominids are usually found
associated with mammalian remains. Little is known, however, about how
closely different mammal species correlate with environmental and climatic
factors. My aim here is to analyse mammalian data to identify the criteria
that relate most strongly to environmental issues. This will be done by
analysing species diversity or richness in mammalian faunas, and so a
secondary question is: what are the determining ecological factors
influencing mammal species richness? If we can explain patterns of species
diversity, we can explain some of the factors underlying ecological
variation, both in the present and in the past. Species diversity varies
latitudinally, with more species in the tropics, declining towards poles.
This is the largest scale and most widely known pattern in ecology, and many
hypotheses have been proposed to explain it, e.g. based on energy input into
the environment or productivity of ecological systems. Species diversity
also varies at different trophic levels, and it has geographic, topographic
and historical components as well, which are superimposed on long term and
short term climatic effects. All these need to be recognized and their
ecological effects analysed before we can apply them to fossil faunas. With
living mammal faunas, we have evidence of their inter-relationships with
climate and environment and how these affect behaviour, and these factors
can be tested by multiple regression to identify significant variables
affecting diversity. With fossils, we have only the composition of faunas,
more often than not biased by taphonomic processes, and the morphologies of
those parts of the animals that have survived the fossilisation process.
These can be compared with both the regression analyses of recent faunas and
the morphologies of extant species so as to interpret their ecological
diversity and subsequently their palaeoecology. Examples will be taken from
Pliocene faunas from East Africa.
|
| |
|
Neanderthals,
climate and human evolution during the last Ice Age |
| Professor
Leslie Aiello |
| Department
of Anthropology, University College, London |
|
Abstract |
|
During the later part of the Late Pleistocene (~60-25ka) Neanderthals gave
way to modern humans in Europe. New research shows that this was a period of
many abrupt alternations between relatively warm periods and cold intervals.
It has also shown that Neanderthal archaeological sites are limited to areas
where the average winter wind chill was above zero degrees Fahrenheit while
contemporaneous and later Aurignacian and Gravettian archaeological sites
(attributed to modern humans) are found in areas of much colder climates.
This suggests that modern people had developed cultural means to cope with
life in areas of Europe that were simply not accessible to the Neanderthals.
Growing knowledge of European climates during the last glacial together with
appreciation of the thermoregulatory limits of Neanderthals and modern
humans, are helping to clarify our understanding of the patterning of human
occupation in ice age Europe.
|
| |
|
Glacial
influences on human migration in tropical Asia |
| Dr
Douglas Brandon-Jones |
| Richmond,
Surrey |
|
Abstract |
|
Homo
sapiens
first reached Java (Indonesia) about 100,000 years ago during the most
recent interglacial. H. erectus first appeared there about 1 Ma,
between major sea level recessions at 2.4 Ma and 0.8 Ma, caused by sea
water freezing into the periodically expanding polar ice-caps. During
these and lesser recessions, land areas increased and, notably in
Pleistocene SE Asia, some islands coalesced to form temporary
subcontinents. It has been presumed that this offered plants and animals,
including humans, the opportunity to disperse from one former (and
present) island to another. The climatological effects of such continental
shelf development, however, have generally been overlooked. Existing
continents tend to be driest in their heartland. Biogeographic, pollen,
fossil and climatological evidence indicates that the temporary
subcontinents in SE Asia and Australasia followed suit. Their mainly arid
climate, inhibiting plant life, created an obstacle, rather than an aid to
dispersal. During interglacials, dispersal by natural rafting between
islands (impossible during glacials, when intervening straits disappeared)
was evidently more frequent and significant than has been supposed.
Results from research on the systematics and zoogeography of the leaf
monkeys (or colobines) are employed to illustrate how climatological
conditions probably profoundly influenced human migration from Africa to
Asia.
|
| |
|
The
possible role of climatic changes in later Pleistocene human evolution and
extinctions |
| Professor
Chris Stringer |
| Department
of Palaeontology, The Natural History Museum, London |
|
Abstract |
|
Problems
of chronological resolution greatly restrict our ability to match the
Pleistocene fossil human succession to detailed palaeoclimatic records.
This talk will address two relevant research areas. The first concerns the
ancient human occupation of Britain, now the focus of a specific project (AHOB).
Human occupation of Britain was influenced by two main factors,
palaeogeography (particularly in relation to the periodic absence of a
land bridge, largely controlled by climate) and palaeoclimate
(particularly influenced by conditions in the North Atlantic). The second
area concerns the European extinction of the Neanderthals and their
replacement by modern humans. Particularly in the latter case, if we can
move beyond reliance on uncalibrated radiocarbon chronologies, we may
eventually be able to correlate human demographic changes, including
Neanderthal extinction, with rapid climatic fluctuations.
|
|
|
