Product Description

How did we ever get ashore? How did we make legs, arms and our extremely complex intelligence? Evolution is one of the most hotly debated areas of popular science. With this book, the author presents an accessible account of one of evolution's great mysteries - how microbes turned into humans.

Product Details

• Amazon Sales Rank: #170725 in Books
• Published on: 1999-11-01
• Original language: English
• Number of items: 1
• Binding: Paperback
• 304 pages

Customer Reviews

Almost like a whale? *
Anyone roughly familiar with the course of evolution knows that somehow, somewhen, some animals emerged from the sea. They became land animals - a lineage of them became us. Yet, looking at life in the sea, the emergence of life on land seems rather narrowly focussed. In the sea there are ten-armed squid, eight-armed octopi and five-legged starfish. Except for insects and spiders, nearly all land life from tiny shrews to the immense dinosaurs are formed on a consistent pattern. We're all four-limbed - we're tetrapods. How did that come about?

In this excellent synopsis of the life in the ancient seas, Carl Zimmer examines not only the animals living there, but the wide variety of environments the sea offers. Where, he asks, would life have found the most advantages? If you have some knowledge of physical limitations about salinity, pressure at depth and vision, the answer seems easy. If you don't, Zimmer carefully explains about the need for sunlight, limited pressure tolerance and available food. This location turns out to be in the shallow zones close to land. The shallow areas of the sea are the tidal zones, and it was there that a particular form of fish achieved particular success. These creatures - the lobe-finned fishes - had capability in changing environments. They may not have flashed through the water like marlin or tuna, but they could manuever when the tide fell. The lobe fin was comprised of a set of bones ending in five final extremeties. Examined closely, they look like a misshapen hand - or paw. And there's always four of them.

These creatures, cumbersome in appearance, still managed to make the transition to a dry environment. There were more than just klutzy-looking paws involved. Zimmer explains how the issues of breathing, digestion, body covering and other factors would all need adjustment to the land environment. Zimmer labels these changes "macroevolution". He uses the term to show how body elements changing required interaction among several areas to become a successful organism adapted to a new realm. Jawbones open or merge, skulls lengthen or grow wide, legs shift in position. And teeth? Ah, there's the real pointer to what land animals modified to survive.

Just when Zimmer has his subjects firmly established in forest and veldt, he must follow some of them back to the sea. The giant sea creatures known as cetaceans were a mystery even prior to Darwin's time. Darwin himself, perplexed by what mechanism could have brought these immense mammals back to their remote origins, offered one solution. Zimmer relates Darwin's idea that a swimming bear-like creature made the transition. Both Darwin and Zimmer acknowledge how unlikely that scenario is. What did take place, however, was unknown for over a century. After numerous false pointers, the precursors of whales turned out to be a low-slung wolf-like animal from what is now Pakistan. Phil Gingerich, scrambling about streamside cliffs in that country, produce Pakicetus. Ears and teeth became the focal point of research in early whales. The change from atmospheric to water hearing, including the trick of echolocation, traces how land animals returned to the sea. Changes in diet are reflected in how teeth are shaped and distributed.

Zimmer's account is a lively read, with good accounts of the paleontology and assessment of evidence. There are excellent line drawings to illustrate the various creatures discussed. As a science writer of excellent reputation, he graces the text with good footnotes and references, tucked away at the back. A fine study in a dynamic field. [stephen a. haines - Ottawa, Canada]

* with thanks and humble apologies to Steve Jones

science made understandable
I did buy this book (Dutch version) about 2 years ago and read it last winter. I was expecting it to be a bit boring (the reason for waiting to read it), and that proved completely long. If the subject arouses some interests in you, the you'll alomost bevming involved in this book as if in a good fiction book. It is realy well-written, easy understandable without becoming simple. An excellent book for people who want to learn something about macro-evolution without wanting to study for years.

Macro-evolution at the water's edge
In this excellent book, Carl Zimmer examines two events in the history of life to illustrate the idea of macro-evolution. They are: the transformation from aquatic animals to terrestrial animals (from amphibious lobe-finned fish to early reptiles) and the return to the sea by the predecessors of whales. These are cases of macro-evolution because they are large-scale changes to body-plans.

Carl Zimmer shows that many of the characteristics that are essential for terrestrial life evolved in fishes primarily for marine life; likewise, the animals that evolved into fully aquatic whales enjoyed exaptations that coincidentally helped them in their new life. ('Exaptation' is Stephen Jay Gould's word for the misleading 'preadaptaion', which signifies a functional shift in an adaptation from one use to another.)

An example of a marine exaptation that was essential for terrestrial life is the lung. An example of an exaptation that helped whales become more aquatic was having their nostrils at the back (rather than the tip) of a long snout. Another example of an exaptation in whales is the separation of the mammalian ear-bone from the skull (a defining characteristic of whales), which allowed the early whales to hear underwater.

Some old theories that must be rejected are that lungs evolved from swim bladders (the reverse is the 'cheapest' theory) and that 'the forerunners of tetrapods lived in drought-prone ponds that could become stripped of oxygen or disappear altogether' (page 101). The old theory says anaerobic ponds caused some lobe-finned fish to develop oxygen-breathing lungs and the ability to cross dry land to find another muddy hole to survive in. In fact, the landscape in which the first amphibians evolved was not so parched as was once thought and the lobe-finned fish that evolved into terrestrial animals lived in the ocean or in brackish inlets (plus the fish that much earlier had first developed lungs were fully marine animals).

Altogether, this is a satisfying, informative and nicely argued book from a perspective that honours the influence of Stephen Jay Gould and is recommended for a well-rounded view of evolution theory.