Manatees With Fingernails

The history of life, on the whole, has been a soggy affair. A vast majority of Earth’s creatures — from kelp to plankton to tube worms — has always lived in the ocean. It was probably in the ocean that life first began four billion years ago, and for billions of years after that emerged from the sea only around 360 million years ago; these recent air-breathing years have been a brief coda to our evolution.

The author and artist Richard Ellis has done a tremendous amount over the years to put things in proportion, to draw our eyes from the land to the sea. He has produced a series of authoritative books on marine life, ranging from sharks to whales to deep-sea ecosystems.

In his latest book, “Aquagenesis,” Ellis writes that “my earlier books were mostly crammed with facts.” If you want to know which species of manatee lack fingernails, Ellis is your man.

In his new book Ellis leaves today’s oceans and sails off into the past, to chart the evolution of marine life. The facts come as fast and furious as before, although many feel strange and a bit alien here, coming as they do from so far in the past and from branches of life long extinct. Ellis describes sharks with coiled lower jaws like spiraled rasps, marauding arthropods with mouths shaped like pineapple rings and ancient whales that looked like furry alligators. His inventory includes the latest fossil discoveries, and it is graced with a number of illustrations from his own pen.

Unfortunately, some of the facts crammed into “Aquagenesis” are wrong. He states, for example, that before the oldest known animal fossils 600 million years ago, the only known fossils are cyanobacteria (better known as pond scum). Actually, fossils and chemical signatures of many kinds of multicellular algae and single-celled protozoans date hundreds of millions before the animals come on the scene. Writing about the “Cambrian Explosion” (the burst of animal evolution that unfolded around 540 million years ago), Ellis claims that ”in the geological instant of 10 million years, the ancestors of all animals appeared.” Except for corals, jellyfish, bryozoans and other major groups of animals whose earliest relatives appear in the fossil record before or after the Cambrian Explosion.

More serious problems lie in the book’s organization and argument. Despite all the details, “Aquagenesis” ends up presenting a narrow vision of the history of the oceans. Ellis takes a quick hop from the origins of life to the dawn of animals, and then spends most of the book describing such vertebrates as fish and whales. In the process, he skips over some of the most significant and interesting stories of evolution that the oceans have to offer. The most important marine animals, for example, may be corals, because they create reefs that serve as the rain forests of the ocean. And the history of reefs is as fascinating as evolution gets. Reefs have existed in one form or another for over half a billion years, but they were originally built by algae, clams and other organisms — before today’s corals came on the scene. Each dynasty gave way to a new one, sometimes vanishing in the blink of a geological eye.

If you are willing to step outside the animal world altogether, the ocean’s microbes are even more significant. Some three billion years ago, bacteria began to make the air breathable, by flooding the planet with oxygen. Microbes have also twiddled with the global thermostat by creating and consuming millions of tons of greenhouse gases every year. Only humans can rival them as planetary engineers. But as important as corals or microbes may be, they have no backbone, and so they get short shrift in this volume.

Ellis clearly wants “Aquagenesis” to be more than an encyclopedia; he wants to present an argument about evolution. He claims that while evolution is real, scientists “haven’t discovered what it is in evolution that causes actual change, or extinction.” That’s a sweeping claim, and one that scientists would dispute. But it’s impossible to evaluate, because the book’s account of evolution doesn’t reflect the true state of the science. For instance, Ellis writes that “the survival of the species . . . is what evolution is about.” The biologist George Williams laid that misconception to rest in the 1960’s, showing how natural selection operates on individuals and their genes.

Elsewhere, Ellis states, without citing evidence to back him up, that “there simply hasn’t been enough time for the tens of millions of life forms now on Earth — and the billions that are extinct — to have developed by the gradual, often accidental process that we call evolution.” He then claims that punctuated equilibrium — a model of evolution in which new species form over tens of thousands of years and then settle into millions of years of stasis — was developed to solve this supposed paradox. But that’s not the case. Two paleontologists, Niles Eldredge and Stephen Jay Gould, proposed punctuated equilibrium as a biological explanation of patterns of the fossil record, not to accommodate Ellis’s alleged time crunch.

It is certainly true that there are many questions about the evolution of ocean life that scientists have yet to answer. Who knows if they’ll ever figure out exactly which ecological factors led our finned ancestors ashore? But imperfect knowledge cannot be equated with absolute ignorance. As Ellis himself recounts, scientists have found a lot of remarkable fossils in recent years, bridging evolutionary gaps that once seemed like giant chasms. They don’t represent complete genealogies, but Darwin warned that scientists should never expect to find one. “The crust of the earth is a vast museum,” he wrote, “but the natural collections have been made only at intervals of time immensely remote.” Instead, they are clues to the steps by which new body plans have evolved.

These disappointments aside, “Aquagenesis” works well when Ellis is in his classic mode, cramming the facts. And when he is paying homage to giant penguins, glowing squid, chambered nautiluses or monstrous marine lizards, he drives home one of the most important features about the evolution of life in the ocean: its ebullience, which, after four billion years, shows no sign of letting up.