Why life on Earth is so diverse
INFINITE LIFE A revolutionary story of eggs, evolution and life on earth
JULES HOWARD 288pp. Elliott and Thompson. £20.
TO PEOPLE WHO NORMALLY encounter them in culinary form, the structure of eggs may seem basic: yolk, white, shell, plus the bits of membrane that make peeling a boiled egg difficult. But in Infinite Life: A revolutionary story of eggs, evolution and life on earth, Jules Howard demonstrates that eggs are anything but simple. Their production is a feat of engineering (the detailed descriptions of “nozzles”, “chemical treatment”, calcium “applied to the egg” and so on, evoke images of a car factory). Internal, external, freefloating, protected by a womb or nurtured by a placenta – they come in an incredible array of shapes, colours, formats, and origins. And they are one of the key reasons that life on Earth is so diverse.
Howard’s book takes its readers on a swift tour of evolution, zoology and palaeontology. Infinite Life is structured chronologically, from the Hadean eon, 4,540 million years ago, to the present day. Each of the eleven chapters addresses a separate era, and each era serves as a pretext to uncover new evolutionary milestones concerning eggs. We find out how – and when – sex came about; how the first eggs looked (“like a distant supernova […], bordered on all sides by a ring formed from some forgotten explosion”); which unexpected species have pouches (woodlice and frogs, among others); and what might have been the purposes of markings and colours of dinosaur eggs.
The decision to arrange the book chronologically, rather than by species or egg type, makes for better storytelling. The contrast between the dramatic evolution of life on Earth and the appearance of something as outwardly mundane as an egg is striking. Howard supplies us with elaborate depictions of the behaviour of ancient animals (a Silurian millipede, say, or a Jurassic egg-eating mammal), and invites us to take a closer look at the “primitive” eggs of corals or sea urchins. “Every floating egg cell … comes packaged up with its own supply of MAAs [amino acids that absorb UV light and act like sunscreen], which the adult organism … divides out into each and every egg like a caring note left in a child’s lunchbox”. Apart from prompting a brief reflection on whether human parenting is on a par with that of the average jellyfish, this description provides a new level of appreciation for invertebrate development: “broadcast spawning is far from a simple evolutionary choice”.
Apart from marvelling at the complexity of eggs, Howard explores the function and necessity of their immediate surroundings: ovipositors, pouches, wombs. He devotes a lot of time to the placenta; in particular to the back-and-forth tug of war betw
