Neogene Paleontology of the Manonga Valley, Tanzania: A Window into the Evolutionary History of East Africa

428 Pages·1997·15.13 MB·English

by  Terry Harrison

Neogene Paleontology of
the Manonga Valley, Tanzania
A Window into the Evolutionary
History of East Africa
TOPICS IN GEOBIOLOGY
Series Editors: Neil H. Landman, American Museum of Natural History,
New York, New York
Douglas S. Jones, University of Florida, Gainesville, Florida
Current volumes in this series:
Volume 2 ANIMAL-SEDIMENT RELATIONS
The Biogenic Alteration of Sediments
Edited by Peter L. McCall and Michael J. S. Tevesz
Volume 3 BIOTIC INTERACTIONS IN RECENT AND FOSSIL BENTHIC
COMMUNITIES
Edited by Michael J. S. Tevesz and Peter L. McCall
Volume 4 THE GREAT AMERICAN BIOTIC INTERCHANGE
Edited by Francis G. Stehli and S. David Webb
Volume 5 MAGNETITE BIOMINERALIZATION AND MAGNETORECEPTION IN
ORGANISMS
A New Biomagnetism
Edited by Joseph L. Kirschvink, Douglas S. Jones
and Bruce J. MacFadden
Volume 6 NAUTILUS
The Biology and Paleobiology of a Living Fossil
Edited by W. Bruce Saunders and Neil H. Landman
Volume 7 HETEROCHRONY IN EVOLUTION
A Multidisciplinary Approach
Edited by Michael L. McKinney
Volume 8 GALApAGOS MARINE INVERTEBRATES
Taxonomy, Biogeography, and Evolution in Darwin's Islands
Edited by Matthew J. James
Volume 9 TAPHONOMY
Releasing the Data Locked in the Fossil Record
Edited by Peter A. Allison and Derek E. G. Briggs
Volume 10 ORIGIN AND EARLY EVOLUTION OF THE METAZOA
Edited by Jere H. Lipps and Philip W. Signor
Volume 11 ORGANIC GEOCHEMISTRY
Principles and Applications
Edited by Michael H. Engel and Stephen A. Macko
Volume 12 THE TERTIARY RECORD OF RODENTS IN NORTH AMERICA
William Korth
Volume 13 AMMONOID PALEOBIOLOGY
Edited by Neil H. Landman, Kazushige Tanabe, and
Richard Arnold Davis
Volume 14 NEOGENE PALEONTOLOGY OF THE MANONGA VALLEY,
TANZANIA
A Window into the Evolutionary History of East Africa
Edited by Terry Harrison
A Continuation Order Plan is available for this series. A continuation order will bring delivery of
each new volume immediately upon publication. Volumes are billed only upon actual shipment.
For further information please contact the publisher.
Neogene Paleontology of the
Manonga Valley, Tanzania
A Window into the Evolutionary
History of East Africa
Edited by
Terry Harrison
New York University
New York, New York
Springer Science+Business Media, LLC
Library of Congress Cataloging-in-Publication Data
Neogene paleontology of the Manonga Valley. Tanzania a window into
the evolutionary history of East Africa I edited by Terry Harrison.
p. cm. -- (Topics in geobiology ; v. 14)
Includes bibliographical references and index.
1. Paleontology--Neogene. 2. Animals. Fossil--Tanzania--Manonga
Valley. 3. Geology. Stratigraphic--Neogene. 4. Geology--Tanzania-
-Manonga Valley. I. Harrison. Terry. II. Series.
QE738.5.N46 1997
560' . 1786'0967827--dc21 97-14542
CIP
ISBN 978-1-4419-3265-5 ISBN 978-1-4757-2683-1 (eBook)
DOI 10.1007/978-1-4757-2683-1
© 1997 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1997.
Softcover reprint ofthe hardcover 1s t edition 1997
http://www.plenum.com
All rights reserved
10 9 8 7 6 5 4 3 2 1
No part of this book may be reproduced, stored in a retrieval system, or transmitted in any
form or by any means, electronic, mechanical, photocopying, microfilming, recording, or
otherwise, without written permission from the Publisher
To the people of Tanzania
who welcomed me into their country
and shared their knowledge and wisdom
Contributors
Miranda Armour-Chelu Department of Anatomy, College of Medicine, Howard
University, Washington, D.C. 20059
Eric Baker Department of Anthropology, Paleoanthropology Laboratory, New
York University, New York, New York 10003
Raymond L. Bernor College of Medicine, Department of Anatomy, Howard
University, Washington, D.C. 20059
Laura C. Bishop Department of Human Anatomy and Cell Biology, University
of Liverpool, Liverpool L69 3GE, United Kingdom
Achilles Gautier Universiteit Gent, Vakgroep Geologie en Bodemkunde, Labo
ratorium voor Paleontologie, B-9000 Gent, Belgium
Alan W. Gentry c/o Department of Palaeontology, Natural History Museum,
London SW7 5BD, United Kingdom
Terry Harrison Department of Anthropology, Paleoanthropology Laboratory,
New York University, New York, New York 10003
Michael 1. Mbago Director General, National Museums of Tanzania, Dar es
Salaam, Tanzania
Medard Mutakyahwa Department of Geology, University of Dar es Salaam, Dar
es Salaam, Tanzania
William J. Sanders Museum of Paleontology, University of Michigan, Ann
Arbor, Michigan 48109
Kathlyn M. Stewart Paleobiology Section, Canadian Museum of Nature,
Ottawa, Ontario K1P 6P4, Canada
Dirk Van Damme Universiteit Gent, Vakgroep Geologie en Bodemkunde, Labo
ratorium voor Paleontologie, B-9000, Gent, Belgium
Jacques Verniers Universiteit Gent, Vakgroep Geologie en Bodemkunde, Labo
ratorium voor Paleontologie, B-9000, Gent, Belgium
Alisa J. Winkler Shuler Museum of Paleontology, Southern Methodist Univer
sity, Dallas, Texas 75275
vii
Preface
In spite of the dedication and resourcefulness shown by paleontologists and
paleoanthropologists over the past seventy years in their quest to find new fossil
hominids, it is clear that, in the enterprise of reconstructing the evolutionary
history of humans (and other mammals), we still have much to accomplish. It is
true that we have made significant advances, with the help of some remarkable
fossil discoveries, in documenting the main phylogenetic strands, but we know
very little about the detailed anatomy or paleobiology of these lineages, or about
the critical events that led to their divergence and subsequent evolutionary
changes. Our image of the early evolutionary history of our own species is based
on a montage of snapshots obtained from fleeting glimpses of the phylogenetic
tree as seen through a few narrow temporal and spatial windows provided us by
the fossil record. If our objective is not simply to fill in the missing gaps, and
thereby document the configuration of the major branches of the human evolu
tionary tree, but rather to gain some real insight into early hominid diversity in
space and time, and to explain this diversity in terms of the complexity of
ecological, geographic, and evolutionary factors that produced it, then we need
a broader perspective. We should strive to improve the quality (not just the
quantity) of the hominid fossil record, so that it includes a wider geographic
coverage and a finer temporal resolution. In order to achieve this objective, the
search for new paleontological sites in Africa, and elsewhere, must be considered
as a high priority. Paleontology is inherently a risky business, with no guarantee
of returns on one's investment, but given the right balance of effort, perseverance,
funding, and good fortune, significant advances in our knowledge of human
evolution can be made. Exciting new finds of Plio-Pleistocene hominids from
Ethiopia, Eritrea, Kenya, Malawi, and Chad provide tangible evidence of such
successes.
The people of Tanzania are justifiably proud of the fact that some of the most
important fossil and archaeological finds pertaining to the earliest stages of
human evolution have been discovered in their country. Olduvai Gorge and
Laetoli are famous throughout the world, and fossil discoveries at these sites
have made a significant contribution toward helping to piece together the
evolutionary history of humankind over the past four million years. Today,
Tanzania is celebrated internationally as a leading center for paleoanthropologi
cal studies. Even so, only three sites in Tanzania have yielded the remains of
early fossil hominids, Olduvai Gorge, Laetoli, and Peninj, all located in the
Serengeti Plains in the northeastern part of the country. This limited distribution
is primarily a consequence of geological factors. The sites cluster at the southern
ix
x
Preface
extremity of the Gregory Rift. where the eastern branch of the East African Rift
valley splays out around the margin of the resistant Tanganyika shield. The rift
valley. and its associated volcanism. provides an ideal geological setting for the
preservation and recovery of fossils. Indeed. almost all of the spectacular early
hominid fossil finds in East Africa are from sites located within the Eastern Rift.
However. another significant factor is that the sites in northern Tanzania are
easily accessible. especially from Kenya. The full paleontological potential of
Olduvai Gorge was not realized until the 1950s. when Louis and Mary Leakey
were able to intensify their explorations from their base in Nairobi. Today it is
relatively easy for expeditions and tourist buses to reach Olduvai Gorge. but
when Louis Leakey began his pioneering work there in the early 1930s. it was a
major logistical problem. Louis Leakey's initial paleontological experiences in
the southern part of Tanzania give some indication of the past difficulties and
dangers involved in mounting major expeditions to the more remote regions of
the country. In 1924. Louis Leakey took part in an ill-fated expedition to the
Jurassic site of Tendaguru. where W. E. Cutler. the leader of the expedition.
succumbed to blackwater fever. Our knowledge of the paleontology and archae
ology of most of Tanzania is quite limited. especially when compared with that
of neighboring Kenya. which has been much more extensively explored. Geolo
gists interested in locating economically important minerals and deposits have
surveyed much ofT anzania. and in the process they have reported finding further
sites with fossils. but very few paleontologists or archaeologists have ever visited
these sites. As a consequence, a large number of potentially important paleon
tological sites remain unexplored.
With this in mind. I began to consider the possibility of developing new
initiatives in Tanzania with the aim of searching for new paleontological sites.
By the early 1980s. I had identified several areas that might prove worthwhile
for further investigation. but it was not until the spring of 1985 that concrete
plans for an expedition began to crystallize. At that time. Michael Mbago from
the National Museums of Tanzania. who was enrolled as a graduate student in
New York University's Museum Studies program. visited my office to introduce
himself. and to announce his interest in studying human evolution. Over the
next few months. Michael and I discussed the prospects of working in Tanzania.
and initially identified the Lake Rukwa basin or the region of Lake Malawi south
of Mbeya as potential areas for exploration. In the summer of 1986. I was able to
make a brief visit to many of the paleontological and archaeological sites in
Tanzania. and to study previous collections of East African fossil mammals in
England. The Natural History Museum in London had a small collection of
unaccessioned fossils made by geologists in the 1920s from the site of Tinde in
the Manonga Valley. This material had never been formally described. although
A. T. Hopwood had made reference to it in a brief note published in 1931.
Hopwood and subsequent workers considered this material to be of Pleistocene
age. However. my preliminary study of the material indicated that the fossils
were probably late Miocene to Pliocene age. Tinde looked like a promising site.
and one that deserved further attention. It was apparently a productive locality
yielding fossils that were at least as old as those from Laetoli. with a fauna
xi
Preface
containing species that were not well known from other sites in Africa, and
located in a region of Tanzania that had not been surveyed since the late 1920s.
Published accounts of the regional geology further indicated that the Manonga
Valley would be a good place to begin the search for productive new sites, with
the potential to yield evidence that might possibly pertain to the earliest phases
of human evolution.
The Manonga Valley in north-central Tanzania, the focus of this volume,
represents a large and previously almost unexplored lake basin, with well
exposed and richly fossiliferous sediments. The sequence of deposits range in
estimated age from late Miocene to early Pliocene (-5.5-4.0 Ma), a slice oftime
that is generally poorly represented in other parts of Africa. In addition, the
Manonga Valley is of special interest in that it is located in a geographic province
that lies just beyond the immediate confines of the rift valley. With its unique
combination of characteristics (Le., it has the oldest fossil mammal localities in
Tanzania, apart from the Jurassic site of Tendaguru, an estimated age range for
the stratigraphic sequence that is generally not well represented in other parts
of Africa, and it has the southernmost localities in East Africa associated with,
but located just outside, the Eastern Rift), the Manonga Valley offers an important
new window into the evolutionary history of Africa.
In 1990, I organized the first Wembere-Manonga Paleontological Expedition
(WMPE), and this was followed by full-scale expeditions in 1992 and 1994. As
director of the expedition I soon learned that establishing a field project at a site
that has little or no prior research history has its problems. To develop a rational
plan of research one needs basic information on the site's geology and paleon
tology. However, this inevitably leads one to a conundrum that is commonly
encountered by researchers. To convince granting agencies to give funds to
support new paleontological endeavors one needs to provide them with the kind
of information that one is requesting money for in the first place! Knowing these
limitations, the goals of the Manonga Valley project have been relatively sim
ple-to find out as much as possible about the geology and paleontology of the
area. This information has provided the necessary empirical foundation on
which to establish a more theoretical, problem-oriented approach. Our initial
objectives for the Manonga Valley project were therefore: (1) to survey for new
paleontological localities; (2) to assess the nature of the geological context of the
major localities; (3) to reconstruct the geological history of the Manonga basin;
(4) to make paleontological collections that would contribute to a better under
standing of the systematics, zoogeography, and evolutionary history of East
African faunas; (5) to obtain more secure estimates of the age ranges of the
fossil-bearing sediments; (6) to reconstruct the paleoecological and paleoenvi
ronmental setting of the lake basin; and (7) to assess the potential ofthe Manonga
Valley for paleoanthropological research.
The contributions in this volume represent the outcome of these research
goals. Chapter 1 provides an overview of the history of research, geology, and
paleontology in the Manonga Valley. Chapters 2 and 3 present details of the
stratigraphy, mineralogy, and geomorphology, and Chapter 4 provides a prelimi
nary synthesis of the taphonomy and paleoecology of the key paleontological