OTHERLANDS

A tour of the past worlds that the geological history of Earth reveals.

British paleontologist and evolutionary biologist Halliday roams the globe to examine the geological maxim that Earth’s past is its present and future—that the processes that once placed the continents into a single supermass will do so again. He begins along the banks of the Thames, which “now enters the sea more than 100 miles south of where it used to flow” thanks to changing sea levels in times of glaciation and glacial melt: Britain was once a tropical swamp. The author recognizes that geologic time is mind-boggling given a record of life that stretches back 4 billion years and a planet another half-billion years older than that. He takes pains, therefore, to write with clarity about what is “directly observable from the fossil record,” allowing for a few alternate theories and surprises. One of the latter is his observation that grasses are only 70 million years old, meaning that grassland animals are younger than that. He chronicles his travels to oddball geological places such as Italy’s Gargano Peninsula, which really belongs out in the middle of the ocean and which was populated “over the water, with ancestrally small animals—mice and dormice, for example, blown across on bits of floating plant, and birds flying over.” The monkeys that made their ways from Africa to South America had a tougher journey, crossing more than 1,000 miles of sea long after the continents broke apart 140 million years ago. Halliday brings good news: After periods of mass extinction come mass flourishing: “A new age begins, with new gods, and new worlds. After death, life; after extinction, speciation.” The bad news: Humans are likely toast all the same.

A bracing pleasure for Earth-science buffs and readers interested in diving into deep history.