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Straight from the Source: Q&A with author Sean B. Carroll Print exclusive
Deep roots: A review of The Hunt for the Dawn Monkey
Whither our rivers?: A review of Disconnected Rivers
Antarctic coastal change and glaciology
Hunt for the Dawn Monkey
by Chris Beard.
The branches of the Tree of Life connect us to all living organisms
and to all organisms that have ever lived. The extinct organisms on the shortest
route through the Tree of Life between modern humans and the root of the tree
are our ancestors; those on nearby branches are our cousins. The longest version
of human evolution would be a journey that starts approximately 3 billion years
ago with the simplest form of life at the base of the tree. It would take more
than 2 billion years to pass up the trunk and along the major branches before
we enter the relatively small part of the tree that contains all animals. Then
we would enter the branch containing all the animals with backbones, then into
the mammal branch, and then into a thin branch that contains one of the subgroups
of mammals called the primates. At the base of this primate branch, we are still
at least 60 million years away from the present day.
The last leg of the human evolutionary journey would take us into the monkey and ape branch of the Tree of Life, and then into the great ape branch. Sometime between 15 million and 12 million years ago, we would move into the small branch that gave rise to contemporary modern humans and to the living African apes. Between 12 million and 9 million years ago, the branch for the gorillas split off to leave just a single slender branch consisting of the ancestors of chimpanzees and modern humans. Researchers estimate that between 12 million and 5 million years, this very small branch split into two twigs. Both twigs end on the surface of the Tree of Life. One has the modern-day chimpanzees at the end of it; the other, modern humans.
Most books about human evolution deal only with the branch of paleontology called palaeoanthropology, which is the science that tries to reconstruct the evolutionary history of the small, exclusively human twig of the Tree of Life. But Chris Beard is a primate paleontologist, not a paleoanthropologist, and his research interest is recovering the evolutionary history of the branch that includes the monkeys and apes, collectively called anthropoids. Thus, Beards book The Hunt for the Dawn Monkey tells the story of his own fossil discoveries, and the way in which they, and his interpretations of them, have turned traditional hypotheses about anthropoid origins on their head. The book also carries important messages for those of us who concentrate on reconstructing human evolutionary history.
The basic classification of living primates we use today was proposed by Reginald Pocock in 1918. It was based on morphology, but it is consistent with the latest molecular evidence. It divides the primates into two groups. One, consisting of the lemurs, lorises and bush babies, is called the Strepsirhini because they have twisted noses. The other, consisting of the tarsiers and the anthropoids, is called the Haplorhini because they have flat noses. Conventional wisdom suggests that the living strepsirhines are more primitive than the living haplorhines. Because of this, many scientists assumed that the earliest fossil primates would be strepsirhine-like, and that only in the later stages of primate evolution would there be evidence of anthropoid-like fossil primates. Because the earliest anthropoids were from sites in Africa (in Algeria and from classic localities in the Fayum region of Egypt), it was assumed that anthropoids originated in Africa.
Beard used similar logic, but different evidence, to come up with a very different hypothesis about anthropoid origins. He concluded that the two major groups of haplorhine primates were more closely related to each other than either was to the strepsirhines. And if the only surviving tarsiers were confined to Asia, then logically the common ancestor of tarsiers and anthropoids, and probably the most primitive anthropoids also, should be Asian creatures. This logic is the same as that used by Charles Darwin when he suggested that modern humans most likely evolved in Africa because our closest living relatives, chimpanzees and gorillas, were confined to Africa.
The book takes the reader through the long chain of events, some of them serendipitous, others the result of a considerable intellect interpreting clues that others were ignoring or misinterpreting. This chain took Beard to sites as far apart as Wyoming and China where he made his influential discoveries. The title is a play on words, referring to the Dawn Man theory, developed by Henry Fairfield Osborn in the early 20th century, which held that modern humans were not closely related to the monkeys and apes, but instead were derived from an ancient ancestor.
I have to confess that in the past when I traced higher primate evolution back much beyond the Miocene, my attention would begin to wander. But Beard had me well and truly hooked. He manages to transmit his own intellectual enthusiasm for a part of the Tree of Life that consists of small shrew-like animals. He is helped substantially by his artist Mark Klingler, whose line drawings are part exquisite naturalistic reconstructions and part explanatory cartoons.
To cut an exceptionally well-told story short, Beard suggests that primates and the rest of the mammal subgroup called the Archonta represent just one twig on what appears to be an exclusively Asian branch of the mammalian family tree. He makes the point that apart from the odd assortment of animals that did originate in Africa the Afrotheres all the other modern mammals that are relatively abundant in Africa today (antelopes, carnivores, etc.) are immigrants (see Geotimes, June 2005).
The debates about the origins of anthropoids and the origins of hominins have much in common. In both cases, researchers disagree about the pattern of evolution and about the role factors such as climate play in shaping macroevolutionary events.
Beard and his editors are to be congratulated. This book is well-written, and it is remarkably error-free. Unfortunately, these are rare attributes, but all the more reason to comment on them. Anyone interested in the history of the science of where we evolved from will appreciate and learn from The Hunt for the Dawn Monkey.
Rivers: Linking Rivers to Landscapes
by Ellen Wohl.
Yale University Press, 2004.
ISBN 0 3001 0332 8.
Ellen Wohl is one of the few front-line earth scientists with a knack for writing
in the environmentalist vein pioneered by John Muir, Aldo Leopold and Rachel
Carson. In Disconnected Rivers, she explores the history of how people
transformed rivers during the expansion of European American settlement and
the economic development of North America.
The title plays on the geomorphological adage that rivers are the circulatory system of their watersheds. In geologic terms, everything we produce, erode or leave around the landscape eventually makes its way down a river (or up into the air). Wohl intersperses personal anecdotes and engaging detours with summaries of technical studies as she creates a detailed portrait of historic changes to river systems across the country. She shows how thinking about rivers in isolation from their watersheds has disconnected waterways from their floodplains and impoverished a foundational element of our natural heritage.
Put simply, this book needed to be written; even disturbed rivers can be beautiful, and most people have little appreciation for how much Americas rivers have changed over the past several centuries. Wohl addresses the effects of mining (the best and most comprehensive treatment of the subject that Ive read), the role of industrial poisoning of rivers (including the famous burning Cuyahoga River in Cleveland), and the 20th century drive of federal institutions to dam rivers for power, flood control, irrigation and water supplies. The book also reviews recent restoration efforts aimed at undoing (or mitigating) the human impacts on rivers that she describes throughout the volume. Although at times a bit too technical for a wide audience, Disconnected Rivers is richly illustrated and full of great examples.
One of the big challenges of the new era of river restoration lies in how concepts and methods developed in one region are mindlessly exported to other regions. Most geomorphologists tend to work in a particular region, and Wohl provides a broad perspective by adopting a national focus and laying out regional differences between rivers in various parts of the country. Making this book required reading for students embarking on careers in river restoration would help them develop the intellectual context needed to understand the rivers and streams they end up working on wherever they practice their art.
Wohl ends by issuing a national rallying cry to respect and conserve rivers, citing Taoist philosopher Lao Tzu as well as her own desire to see American rivers restored to functional, connected systems. After reading Disconnected Rivers, I am reminded that although we are already some way into the century of environmental restoration, we still have a lot of work to do.
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ice, in its various forms, makes Antarctica home to the most dynamic coastlines
in the world. Changes in climate directly affect the volume of coastal ice in
Antarctica, and the volume of water trapped in Antarctic ice is capable, if
released, of significantly raising sea level worldwide. These far-reaching effects
make documenting and understanding changes in coastal Antarctica of the utmost
importance. The U.S. Geological Survey (USGS) Coastal Change and Glaciological
Maps of Antarctica Project is documenting that change and making an inventory
of glaciers in a series of 23 1:1,000,000-scale maps and a single comprehensive
1:5,000,000-scale map, covering the entire coastline of the continent.
New maps of Antarctica evidence the rapidly changing coastlines of the continent. Letters here correspond to 23 areas, charted individually in 1:1,000,000-scale maps. Courtesy of Kevin M. Foley.
The primary source of data used in compiling the maps is the 30-plus-year record of coastal Antarctica generated by Landsat. The Landsat satellites provide geographic coverage poleward to approximately 81.5 degrees south latitude, which proves sufficient for most coastal areas.
The Coastal Change and Glaciological Maps of Antarctica are produced in cooperation with other Antarctic mapping groups, including scientists from Italy, Russia, Norway, Canada, Australia, Argentina and Germany. USGS produced the three maps covering the Antarctic Peninsula in close cooperation with the British Antarctic Survey, and the Bundesamt für Kartographie und Geodäsie provided a tightly ground-controlled mosaic of Landsat images for use as a base for mapping. The RAMP AMM-1 SAR image mosaic of Antarctica is the mapping base for the remaining 20 maps, and along with MODIS imagery, charts features that are south of the geographic limit of Landsat. Other data sources include aerial photography, maps, field surveys and logs, some dating back to the 1800s.