A (VERY) SHORT HISTORY OF LIFE ON EARTH

The title tells it all.

Nature senior editor Gee spends only two pages on the beginning of Earth, when a cloud of dust circling the sun coalesced into a planet about 4.6 billion years ago. The infant Earth was molten rock that eventually cooled enough for atmospheric water to condense into oceans, and it’s amazing, as the author rightly notes, how quickly it appeared—perhaps 100 million years after the planet formed. Early Earth lacked oxygen, so there was no ozone layer in the upper atmosphere to block the sun’s ultraviolet rays, which sterilized everything above the surface of the sea. Consequently, primitive bacteria lived deep in the ocean for at least 1 billion years until some evolved pigments that absorbed these rays to produce sugar. This was photosynthesis. Its fiercely reactive waste product, oxygen, produced the first mass extinction of life that had evolved in its absence. As Gee relates, it was another several billion years before primitive bacteria (prokaryotes) evolved into advanced bacteria (eukaryotes), which accelerated evolution, forming multicellular life forms by 800 million years ago as well as the first animals—sponges. Life moved onto land 500 million years ago and broke its dependence on the sea not through legs (some fish have legs) but with hard-shelled eggs and seeds. Racing through dinosaurs and mammals, Gee introduce apes less than two-thirds into the text and hominins a few pages later. Readers should be chastened at his conclusion, shared by most scientists, that Homo sapiens is making its habitat—the Earth—progressively less habitable and will become extinct in a few thousand years. For a primer on evolution, readers might prefer Andrew Knoll’s A Brief History of Earth (2021) for one reason: illustrations. Gee writes lucid, accessible prose, but readers of his thorough descriptions of long-extinct creatures or explanations of how body parts evolved will yearn in vain for pictures.

A serviceable history of life that one wishes were more comprehensive.