Infinite Life

September 1, 2024
Science journalist Howard (Wonderdog, 2022) chose an unusual subject for his latest book, the evolution of the egg. He begins with the Hadean Eon (4.5 million years ago) and in short, insightful chapters moves to the Cambrian, Ordovician, and on through the entire stretch of prehistory to the current era. Transfixed by the most minute aspects of egg development, he pays animals only glancing interest, preferring, instead, to focus on the vehicle in which animals, insects, and humans come to be. He notes "evolutionary flashpoints," when the egg leaped forward to a new achievement (the placenta being the most recent), while acknowledging there are some periods in the distant past in which information about the nature of eggs remains a mystery. Most surprising is how recently fossilized eggs were discovered; Howard's delight over the 2009 find of mesosaur eggs is palpable. His excitement is infectious and indicative of his approach to the entire book. This is an author who has found joy in his research, joy in his writing, and joy in sharing what he learned.

COPYRIGHT(2024) Booklist, ALL RIGHTS RESERVED.

August 15, 2024
Most animals begin as eggs, and this is their story. British science writer Howard, author ofDeath on Earth: Adventures in Evolution and Mortality, suggests that animals are simply vehicles to produce more eggs, and then he makes an entertaining case for that proposition. Life began nearly 4 billion years ago, but eggs came late. Until about 650 million years ago, tiny organisms often walled themselves off from a hostile environment in a mostly impermeable cyst, ready to reactivate when the good times came back. Beginning at this period their fossils began to reveal tiny collections of cells that resemble embryonic structures that will develop into new life. These were the first eggs, likely from ancient jellyfish and their kin. Working chronologically, Howard writes that by the Devonian Period, about 400 million years ago, "the egg had evolved a new place to hide in the ocean; no longer only found in pouches, or glued to rocks, the egg now occupied a new, secure space, inside the body of the female fish." Many remained long enough to hatch, and this is not a modern development; live births are common in insects and ancient sharks. Land animals flourished well before the Permian Period (roughly 300 million years ago), which also saw the appearance of the amniotic egg that contained fluid-filled membranes surrounded by a hard cell to protect the embryo, allowing it to be laid on dry land. The egg reached its epitome in the mammal placenta, "the life-giving interface between mother and offspring," allowing passage of energy and oxygen and extraction of waste but keeping what is essentially a foreign body separate from the mother's immune system. Animal evolution is a snap compared to the minutia of animal physiology, but Howard has done his homework and delivers a painless but lucid education on a central feature of life. High-quality natural history.

COPYRIGHT(2024) Kirkus Reviews, ALL RIGHTS RESERVED.