A Brain for All Seasons: Human Evolution and Abrupt Climate Change

by William H. Calvin

Book Overview

One of the most shocking realizations of all time has slowly been dawning on us: the earth's climate does great flip-flops every few thousand years, and with breathtaking speed. In just a few years, the climate suddenly cools worldwide. With only half the rainfall, severe dust storms whirl across vast areas. Lightning strikes ignite giant forest fires. For most mammals, including our ancestors, populations crash.

Our ancestors lived through...

• Format: Hardcover
• Language: English
• ISBN: 0226092011
• ISBN13: 9780226092010
• Release Date: April 2002
• Publisher: University of Chicago Press
• Length: 352 Pages
• Weight: 1.28 lbs.
• Dimensions: 1.0" x 5.8" x 8.7"

Customer Reviews

A Fascinating Account of How Abrupt Climate Changes might Have Affected Human Evolution

Human evolution is one of the great detective stories of the twenty-first century. How did this species, Homo sapien sapiens, come to be? Our written record provides some details for only about the last 10,000 years, but what about the millions of years on Earth beforehand? Charles Darwin's rock-solid theory of natural selection, while attacked from the political and religious right as unable to explain the "miracle" of life in the universe without reference to God's creation, remains at the center of all explanations that take a scientific perspective on the subject. William H. Calvin, on the faculty at the University of Washington's School of Medicine, offers in "A Brain for All Seasons" a modification of Darwin's theory that is both illuminating and reasoned. He argues that while Darwin thought in terms of eons of time and slow progression across thousands of generations, some evolutionary processes might be more immediate and striking. Specifically, Calvin asserts that the capacity and complexity of the human brain grew significantly in response to cataclysm on the Earth. Cycles of radical and abrupt climate change, warm-and-wet versus cold-and-dry, help to explain the current state of human evolution. Ancient humans were driven to adapt within a few generations to abrupt climate change, a set of cycles between ice ages and warm seasons, forcing biological as well as other changes on those who survived (and probably few did). These "whiplash" climate shifts, as Calvin calls them, meant that those most adaptable survived and others did not. One major aspect of adaptability is brain power and reasoning. While not exclusive to Calvin, other scientists have made this case effectively, "A Brain for All Seasons" offers a reasoned, accessible explanation of how humanity came to be as it is today. It also offers a cautionary note about the potential for future abrupt climate change and what it might portend for the future of humanity. Wars over land and resources appear almost a certainty, he contends. Widespread starvation and death will also result. And again, those with the most adaptability will survive. William Calvin's analysis is erudite and thought-provoking. It is also highly entertaining. Written as a travelogue that stretches across the globe, especially Africa and the Arctic, "A Brain for All Seasons" serves as an entrée for a lay audience into the world of paleobiology. Calvin does a good job of speaking to that broad audience, but as is the case with most books that seek to communicate scientific knowledge to non-scientists this one sometimes oversimplifies and overstates the evidence. It should be read, as should all books, with a critical mind, something that I'm sure William Calvin would appreciate. Taken altogether, however, it is a useful starting point in understanding how humans evolved from the distant past.

Challenging but well worth reading

This is not an easy book to read. Calvin aims high, setting out to present a coherent new model of how repeated, abrupt climate changes may have driven the evolution of the human brain. Since science has only known about Earth's history of climatic instability for a few years and many details remain to be filled in, Calvin has taken on a major challenge. As if that were not enough, in the second half of _A Brain for All Seasons_, he presents the latest ideas about the mechanisms that may have shifted the global climate from extreme to extreme in the past and may do so in the future, and presents an insightful analysis of the risks involved in our present denial-driven do-nothing approach toward climate change. Unfortunately, a lot of the book reads as though Calvin were thinking out loud. He tends to follow his chain of thought wherever it leads at the time, which I found quite frustrating early on. However, he eventually weaves together the many strands he's mulling over, often in an original and thought-provoking way. If you come away from the book with a clear understanding of his two main ideas, (1) that repeating cycles of large, abrupt climate shifts have taken place over the course of human evolution and provide a convincing ratcheting mechanism for increased brain size and complexity, and (2) that we urgently need to move past the now headshakingly stupid debate about whether or not human-induced climate change is real to a pragmatic analysis of the risks looming ahead and our options for dealing with them, it's well worth a bit of frustration at his style. In the end, I found the book more than worth the effort. Robert Adler Author of _Science Firsts: From the Creation of Science to the Science of Creation_, (John Wiley & Sons, 2002)

Glacial gymnastics

Among the many mysteries surrounding human evolution is the "kick start" our cognitive abilities achieved compared with the other primates. This rapid enhancement has been attributed to many causes, new tool use Calvin, whose neuroscience qualifications are impeccable, offers a fresh view. In so doing, he doesn't cease speculating on how we got to be how we are, but takes a further step in suggesting where we might be going. And how to avoid getting there. The human brain is neither an inevitable progression, nor a divine gift, he argues. It's the result of raindrops ceasing to fall on our heads. Climate, he argues, made us what we are. Equally, it may undo us.Calvin sets the scene at the time when climate changes forced the shrinking of the forest cover in East Africa. Our barely upright ancestors, in coping with the changing environment, learned survival skills on the savannah, then spread out over the globe. During our migrations, various new climatic conditions were being established . The suture of Central America joining North and South America set new wind and current patterns around the globe. The resulting North Atlantic Current [the Gulf Stream] and the temperature and salinity exchanges in that ocean have proven a major factor in climate. Calvin examines what is known about these mechanisms and the impact of variations. The most significant new knowledge refutes the established idea that climate changes gradually. Sudden, wild "flips" of temperature, rainfall and snow cover are now seen as the norm, not as aberrations. Change isn't on the order of centuries, but in years.Calvin's technique of presenting his ideas is as novel as his thesis. Each chapter is an "electronic seminar" with "lectures" and questions arriving for the reader's scrutiny from locations all over the globe. Calvin thus presents himself as a field investigator, relating what on-site researchers are revealing. And much, indeed, is being exposed for assessment. Records from Greenland ice and other sources indicate "chattering" patterns of weather change. These and other finds are related and discussed. And presented for the reader to ponder. If the text doesn't give you reason to pause and reflect, there are numerous striking photographs and diagrams to seize your attention. A Glossary and excellent Further Reading section complete a work of striking significance. If you delay reading this, you may find yourself having to don mittens to take it up. Read it NOW! [stephen a. haines - Ottawa, Canada]

I couldn't put it down

Yes, as a few other reviewers have noted, this book is written in a rather eccentric style. That, however, was only a problem for me when I went looking for things I'd read and discovered the table of contents made no sense. On the other hand, the writing is conversational and detailed, thorough and startling. This is one of those books "everybody should read," because the information in it - particularly in the last third - is so incredibly critical to the fate and future of the human race. Calvin has done one of the best jobs I've seen of explaining how and why the Atlantic currents transport heat and salt - and what happens when they shut down, plunging the entire world into an ice age in as little as 3 to 12 years. (This isn't a just a future threat - it's also an observation of times past. Every ice age has started and ended in fewer than a dozen years!) Calvin tells us in detail how Europe will be devastated by the next ice age, how our SUV usage today in North America is leading us right to it (and much sooner than most think), and - most amazingly - offers some specific suggestions about things that can be done to stop it (like daming up some fjiords in Greenland and dynamiting others). Along the way, we also get a completely new view of human evolution, based in the whiplash environment humans survived for the past 200,000 years. This book is brilliant, and I highly recommend it. Just be sure to mark up the pages as you read them, because that's the only way you'll be able to find things later when you try to explain it to your friends (as you will want to do!).

Our brains have had a rough time for two million years!

...I consider myself up-to-date on the topic of human origins and the influence of climate change on human evolution, and I learned a few things reading this book. Such as: 1) changes in wetness/dryness patterns seem to have a much greater impact on our fate than temperature changes. 2) climate changes may have had a much greater role than previously thought on the evolution of generalized altruism (sharing with strangers not your immediate kin) as an adaptive human trait.3) if we continue to emphasize maximizing efficiency as the goal of world gloabalization, we are truly [doomed] when the rules of the game change with the next RCCE ("rapid climate change event"), which appears to be happening as you read this.It is true that the book could have benefited from additional editing and it does tend to ramble a bit from topic to topic, but the author's conversational style kept my interest, and he does a good job of mixing in humor. At one conference he attended the question of interbreeding with Neanderthal women came up as a possibility. One expert was asked if he believed the rate of interbreeding could have been as high as two percent. Two percent?! It is a fact that more than 2% of the male human population would mate with sheep! And they aren't even a closely related species!Looking where we've been as a species can provide some important guideposts to where we are headed next. The lifeboat has gotten much smaller many times in the past, and there are a lot more of us in the lifeboat this time. The message of this book is an important one. It glosses over the details sometimes, but you are not going to remember all the details anyhow. Humans learn best through storytelling rather than statistics, and Calvin is a good storyteller.