THE EQUATIONS OF LIFE

An insightful argument that evolution, despite producing complex creatures as different as bacteria, bugs, and humans, must obey scientific laws.

“Physics explains much about why living things look like they do; evolutionary biology provides much of the explanation about how they become like they are.” So writes Cockell (Astrobiology/Univ. of Edinburgh; Astrobiology: Understanding Life in the Universe, 2015), the director of the UK Centre for Astrobiology, in his latest, and he proceeds to make a convincing case. Laws set limits. There is life at temperatures above that of boiling water and below freezing, but not by much. When water is absent or locked up in extremely salty environments, life cannot exist. Honey doesn’t spoil not because it contains any toxins but because its water is unavailable. Our planet’s life is carbon-based and requires a universal solvent, water. Might creatures elsewhere in the universe form themselves from closely related silicon and prefer other common liquids such as ammonia or methane? Moving smoothly from physics to chemistry, biology, and beyond, the author is an amiable guide through some knotty scientific thickets. Ignoring the taboo on equations in popular science writing, Cockell sprinkles them liberally to illustrate their (relative) simplicity. Perhaps the simplest, P = F/A (pressure equals force over area), is critical to the mole, a burrowing animal designed to shift soil by maximizing the force over a small area. Evolution eliminates less efficient burrowers, so all moles, many entirely unrelated, look alike. “If physics and biology are tightly coupled,” writes Cockell, “then life outside Earth, if such life exists, might be remarkably similar to life on Earth, and terrestrial life might be less an idiosyncrasy of one experiment in evolution, but a template for much of life in the universe.”

Many readers will find the equations incomprehensible, but they will relish a lucid, provocative argument that the dazzling variety of organisms produced by 4 billion years of evolution may seem unbounded, but all follow universal laws.