As the British naturalist marks a milestone birthday, we take a look at how his work has shaped science.

Deep in the rainforest of the Virunga Mountains in Rwanda, David Attenborough watches as a troop of mountain gorillas ( Gorilla beringei beringei ) play in the undergrowth around him. One — a youngster — crawls onto his lap and tugs at his clothes. It is January 1978, and the cameras are rolling on a wildlife series called Life on Earth .

Credits: John Sparks/Nature Picture Library; BBC/Everett Collection; Nick Upton/Nature Picture Library

Credits: John Sparks/Nature Picture Library; BBC/Everett Collection; Nick Upton/Nature Picture Library

Although not his first on-camera appearance, it would prove to be a defining one for the British naturalist: around 15 million viewers in the United Kingdom tuned in to watch the television series when it aired on the BBC in 1979.

A series of three photos of David Attenborough sitting in front of the wide expanse of the Grand Canyon in the U.S.; holding two large…