MacPhee - End of the Megafauna

Sabertooth cat, Smilodon fatalis, continental Americas.

Copyright 2019 by Ross D. E. MacPhee

Illustrations copyright 2019 by Peter Schouten

All rights reserved

First Edition

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The Library of Congress has cataloged the printed edition as follows:

Names: MacPhee, R. D. E., author. | Schouten, Peter, illustrator.

Title: End of the megafauna : the fate of the worlds hugest, fiercest, and strangest animals / Ross D.E. MacPhee ; with Illustrations by Peter Schouten.

Description: First edition. | New York : W.W. Norton & Company, [2019] | Includes bibliographical references and index.

Identifiers: LCCN 2018029730 | ISBN 9780393249293 (hardcover)

Subjects: LCSH: Morphology (Animals) | Body size. | Extinct animals. | Extinction (Biology)

Classification: LCC QL799 .M3227 2019 | DDC 591.4/1dc23

LC record available at https://lccn.loc.gov/2018029730

ISBN: 9780393249309 (ebk.)

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Key-foot glyptodon, Glyptodon clavipes, South America. The rufous oven bird (on carapace), Funarius rufus, and the buff-necked ibis, Theristicus caudatus, are both extant.

[W]e are in an altogether exceptional period of the earths history. We live in a zoologically impoverished world, from which all the hugest, and fiercest, and strangest forms have recently disappeared.... Yet it is surely a marvelous fact, and one that has hardly been sufficiently dwelt upon, this sudden dying out of so many large mammalia, not in one place only but over half the surface of the globe.

ALFRED RUSSEL WALLACE,

The Geographical Distribution of Animals (1876)

L ike other environmental hot-button issues familiar to us todayocean pollution, forest loss, climate change, species endangerment, pathogen proliferation, the plasticpocalypse, and many othersbiological extinction is very much in the public eye. This is surely a result of the growing realization, which now seems utterly inescapable, that humans have created, and continue to create, the kinds of circumstances in which species die out well before their time. A few generations ago people were more negligent in their understanding of many things, including our long record of environmental despoliation, because the necessary facts were either unavailable, difficult to acquire and interpret, or frankly irrelevant to their immediate concerns. In the digital age, it is no longer possible to claim ignorance or lack of readily accessible information. Although it may be true that as we have learned more about human impacts we have come to despair more, the antidote to this is knowledge, for knowledge is the essential basis for informed action.

In this regard, it has often been claimed that the past record of human interactions with the worlds biotathe sum total of living thingsshould have something to tell us about what to expect in future. But this requires that we ask the right questions, not only about what happened in previous times, but also how it happened.

To do this we need to go to the borderland between archeology and paleontology, the sciences that together attempt to document and explain past life in all its abundance and complexity. End of the Megafauna is specifically concerned with examining the enigmatic disappearance, in mostly prehistoric but still relatively recent times, of a major fraction of Earths truly large vertebrates as well as many of their smaller relatives. These losses seem to have occurred quite quickly within any given area, although on a worldwide basis the full process took several tens of thousands of years to finishif it is in fact finished.

Popular works tend either to assume the cause of these losses is settled or to treat differing viewpoints about causation in a superficial manner. This book takes a different tack, by concentrating on how scientists who study these mysterious disappearances have attempted to explain them. We will be looking at the strengths of their arguments as well as their limitations, because challenge and response is what good science and good scientists are all about. To make discussion worthwhile, some technical concepts have to be introduced, but I have tried to present them in an appetizing manner. Since there is no way I could cover more than a fraction of the scholarship that is relevant to this endeavor, I have purposely chosen to emphasize themes that strike me as the most interesting.

Most paleontologists work in deep time, the distant past, where intervals are measured in millions of years. I study events that, geologically speaking, happened almost yesterday. The losses covered in this volume have been called late Quaternary extinctions, Ice Age extinctions, Late Pleistocene/Holocene extinctions, Anthropocene extinctions, megafaunal extinctions, and modern-era extinctions, depending on when exactly they occurred and what aspects are being emphasized. (Here and throughout, consult the glossary for unfamiliar terms.) These labels overlap to a greater or lesser degree, but have different connotations depending on whos doing the defining. The result is potential confusion in the minds of readers. Although I will use some of these alternative wordings from time to time to add variety to my text, I prefer to use the phrase Near Time extinctions to encompass all vertebrate losses, however caused, that took place during the past 50,000 years or so. Near Time extinctions as a label has the advantage of being outside the system of formally named intervals that scientists use, yet it embraces the relevant parts of all.

At the same time, Near Time is no more homogeneous than any other period in Earth history, so I take care not to overgeneralize. One distinction I will make throughout is between very late losses, or ones that occurred in the mid-Holocene or later (last 5000 years), and those that occurred appreciably earlier. Scientists are in general agreement that losses in very recent times were fundamentally anthropogenic (that is, human-induced), even if there are uncertainties about what combination of alien species introductions, environmental degradation, and perhaps other factors caused specific disappearances. Although I dont ignore these later extinctions, most of which occurred on islands, my intention is to concentrate on earlier disappearances because there is no consensus regarding their fundamental causation. Compared to very recent losses, the level of uncertainty about what really happened to force these earlier extinctions is much greater, the relevant evidence much thinner, and the explanatory stakes correspondingly higher.