The drive to explore, to set out on journeys to distant lands and across horizon-less oceans, may be inseparable from human nature itself, says Stewart Weaver, professor of history. Whether crossing a land bridge over the Bering Strait 12,000 years ago, diving to the depths of the seas, or launching probes to the edge of the solar system, humans seem to have a compulsion to discover what’s “out there.”

“For all the different forms it takes in different historical periods, for all the worthy and unworthy motives that lie behind it, exploration—travel for the sake of discovery and adventure—is, it seems, a human compulsion, a human obsession even (as the paleontologist Maeve Leakey says); it is a defining element of a distinctly human identity, and it will never rest at any frontier, whether terrestrial or extraterrestrial,” says Weaver, the author of a new book, Exploration: A Very Short Introduction (Oxford University Press, 2015).

In the short primer on human exploration, Weaver offers brief accounts and assessments of explorers well- and little-known and places them in the context of natural history.

“A true explorer,” he writes, “is a traveler who seeks a discovery.”

Here’s a quick tour of those travels.

Pytheas of Massalia: 315 BCE

The Greek geographer was the first-known reporter of the arctic and the midnight sun. Conservative estimates credit him with about 7,500 miles of ocean travel, taking him from the Bay of Biscay to circumnavigate the British Isles.

Zheng He: 1405–1433

The “Grand Eunuch” and court favorite of the Yongle Emperor of China led seven expeditions through the Indian Ocean. The first voyage included 62 ocean-going junks—each one perhaps 10 times the size of anything then afloat in Europe—along with 225 smaller support vessels and 27,780 men. With Zheng He’s death at sea in 1433, the fleet was broken up, travel forbidden, and his name expunged. In 1420, Chinese sailors had no equal in the world. Eighty years later, scarcely a deep-sea-worthy ship remained in China.

Bartolomeu Dias: 1488

The Portuguese commander was the first European to round the Cape of Good Hope. Dias was trying to find an ocean passage to India when he rounded the southern tip of Africa without realizing it.

Christopher Columbus: 1492

Columbus was searching for a westward route to China when northeast trade winds swept his flotilla across the Atlantic in just 33 days. The routes he pioneered and the voyages he publicized altered European conceptions of geography and led almost immediately to European colonial occupation of the Americas, permanently joining together formerly distinct people, cultures, and ecosystems.

—Monique Patenaude