Sir David Attenborough is one of the great naturalists of our time, celebrated for decades of peerless documentary making, an infectious love of the animal kingdom and that distinctive and enthusiastic whisper. Once criticized by campaigners for his reticence to address contentious issues, Attenborough is no longer willing to speak in hushed tones.

Sitting opposite the kangaroo enclosure at London Zoo, he told The Daily Beast he had lost patience with the “ignorance” of creationists, polluters, and climate change deniers. “To simply say that you must accept unquestioningly what you learned at your mother’s knee is not the act of an intelligent person,” he said.

It was a rare flash of frustration from a man who has spent more than 60 years in the public eye. He now walks with the aid of a stick but thanks his “lucky stars” that he is still making wildlife documentaries at the age of 87. As I arrived to meet him, he was describing to a former colleague how a cameraman had recently asked him to look directly into the lens while filming a segment instead of turning to face the creature that he was holding in his outstretched left hand. “How could I be so disrespectful?” he said. “No one wants to look at me.”

But we have been happily looking at him since the 1950s. In the U.S. Attenborough is perhaps best known for the Life on Earth series that was broadcast on PBS in the 1980s, on the other side of the Atlantic he is an institution, recently winning a BBC poll to find the greatest living British icon. His work has often been diluted for an American audience, with his masterful narrations for Planet Earth and Life re-recorded by Alec Baldwin and Oprah Winfrey before they were broadcast on the Discovery channel. There have also been accusations that the U.S. network sought to downplay climate change in the shows.

In fact, Attenborough says he has finally grown sick of America’s attitude to climate change. “I think it’s very sad that people won’t accept evidence for what it says—it’s extraordinary that one of the wealthiest, materially advanced societies in the world can support irrational myths in that way,” he said. “That they should do it privately is up to them but since what they do effects that whole world it’s pretty serious that they should not accept that humanity has been responsible for these changes that are absolutely evident to everyone else.”

You could hardly describe the response as knee-jerk since Attenborough has made a career of resisting controversy, often describing himself as “a reporter” with no views of his own. He does also have sympathy for those who resist the prevailing science on climate change. “There are very good reasons why people should not wish to accept it, because it interferes with their business,” he said. “I would much prefer it wasn’t true—but it is true and unless we can do something about it we are going to be in trouble.”

He has less time for those who deny the existence of evolution, however. “Every society in the world has found it necessary to produce a story to account for the fact that humanity is on earth,” he said. “The Australian Aboriginals think that the first humans were regurgitated by a great rainbow serpent in the sky, the people in Thailand think the beginning of the world was a huge pool of milk and a snake was pulled by demons, and the milk coagulated and that formed human beings and there was a time, two and a half to three thousand years ago, when people on the east end of the Mediterranean thought woman was made from the rib of the first man.

“If somebody says to me I believe every word of the Bible is true, you can’t argue against that degree of irrationality…there is actually a way of looking at the natural world and seeing the evidence and it’s all there. And what’s more it’s the same evidence whether it’s in Australia or Northern Europe or wherever. It’s all the same—it all produces the same answer and you can all see the evidence—if you reject that then there’s nothing I can say.”

Attenborough and his fellow naturalists have been demonstrating the science behind evolution and the fossils that show the development of animal species for decades, and yet recent years have seen an uptick in the number of Americans who believe God put humans directly on earth. One suggested explanation, has been the surge of unchecked disinformation available online. “Never before in history has the entire world been able to speak to one another. We are at the beginning of an extraordinary evolution as a species—one species is able to communicate instantly with every member,” Attenborough said. “I’m not so cynical as to think that ignorance will always win.”

Far from cynical, Attenborough’s eyes still glint with a boyish enthusiasm when he returns to the latest discoveries about the natural world. “We found a scientist in Bristol who discovered that plant roots not only make subsonic sounds when they go down but other roots hear them and react,” he explained, with hands recreating the subterranean movement. “What happens is that the root goes down and this root will grow in an opposite direction. The mechanism nobody had known before. It’s completely new!”

With his 90th birthday on the horizon, he says he has no plans to give up making documentaries. “It isn’t because I exercise, or diet, or live a virtuous life or something, it’s just that fortunately my legs still work, they don’t work as well as they did, but they can get me around,” he said. “That I should be invited to keep doing it is just a huge delight and privilege, and I propose to take advantage of it.”

David Attenborough’s show Natural Curiosities will be broadcast in the UK on Tuesdays at 8pm from February 18, on Watch.