Book review -- evolution and geography

Here Be Dragons by Dennis McCarthy (2009)

Biogeography is the study of the global distribution of living things and the interaction of geological change, especially plate tectonics, with biological evolution.  It's not really a new field -- biogeographical concepts played a role in Darwin's discovery of natural selection -- but its implications and contributions aren't widely recognized by laymen.  This book (buying info here) gives a good overview of its explanatory power -- why certain kinds of animals are almost never indigenous to islands, why the life forms of the southern continents are so different from those of the north, the dramatic and sometimes catastrophic effects of continental drift, and why invasive species and the ecological disruption they cause have been a part of the story of life since long before modern times or even the appearance of humans.

The book is somewhat reminiscent of Jared Diamond's Guns, Germs, and Steel, which it cites several times -- the impact of geography on biological evolution somewhat parallels its impact on human cultural development, though obviously over a far longer time frame.

Most people are familiar with the separation of South America from Africa in the late dinosaur period, but actually the most important biogeographical event in Earth's history was the break-up of the ancient southern super-continent of Gondwana into the land-masses which eventually became Africa, South America, India, Australia, and Antarctica.  This caused the native Gondwanan species to diversify in often-surprising ways, though much of the animal and plant life of those lands remains noticeably similar (and somewhat bizarre-looking to northern-hemisphere humans).  It also led to the freezing-over of Antarctica, reducing a once green and teeming continent to the icy wasteland we see today.

Quality of writing can be as important to readers as the information being presented, and Here Be Dragons tells its story in a gripping way.  It's at its best in the chapters "The Volcanic Ring that Changed the World" and "The Bloody Fall of South America", illuminating the icy death of the Antarctic biosphere and the effects of the invasion of North American predators into formerly-isolated South America after the formation of the isthmus of Panama just a few million years ago.  These episodes of mass death and extinction, among the worst in the planet's history, get the dramatic treatment they deserve.

There's also a particularly interesting digression on the orca, a highly-intelligent sea mammal which seems to be divided into at least three subgroups which operate more like human cultural or ethnic groups than biological subspecies.

Toward the end, the book touches on a more controversial topic -- the diversification of humans as they spread around the globe.  In fact, humans are a remarkably homogenous species considering the vast range of lands we inhabit -- less genetically diverse than chimpanzees, despite the latter being confined to a narrow belt of habitat across Africa.  But genetic differences between human populations do exist.

Even if you already have a good general understanding of evolution, you'll pick up some new insights from this.  Thanks to Carol Seidl for bringing the book to my attention.