An Interview with Andy Knoll
What are the origins of life? How did things go from non-living to living? From something that could not reproduce to something that could? One person who has exhaustively investigated this subject is paleontologist Andrew Knoll, a professor of biology at Harvard and author of Life on a Young Planet: The First Three Billion Years of Life. In this wide-ranging interview, Knoll explains, among other compelling ideas, why higher organisms like us are icing on the cake of life, how deeply living things and our planet are intertwined, and why it’s so devilishly difficult to figure out how life got started.
NOVA: When people think of life here on Earth, they think of animals and plants, but as you say in your book, that’s really not the history of life on our planet, is it?
Knoll: It’s fair to say when you go out and walk in the woods or on a beach, the most conspicuous forms of life you will see are plants and animals, and certainly there’s a huge diversity of those types of organisms, perhaps 10 million animal species and several hundred thousand plant species. But these are evolutionary latecomers. The history of animals that we’ve recorded from fossils is really only the last 15 percent or so of the recorded history of life on this planet. The deeper history of life and the greater diversity of life on this planet is microorganisms—bacteria, protozoans, algae. One way to put it is that animals might be evolution’s icing, but bacteria are really the cake.
NOVA: So we live in their world rather than the other way around?
Knoll: We definitely live in a bacterial world, and not just in the trivial sense that there’s lots of bacteria. If you look at the ecological circuitry of this planet, the ways in which materials like carbon or sulfur or phosphorous or nitrogen get cycled in ways that makes them available for our biology, the organisms that do the heavy lifting are bacteria. For every cycle of a biologically important element, bacteria are necessary; organisms like ourselves are optional.
NOVA: What is your definition of life?
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