Science in Mind

Harvard scientist calls for an integrated approach to studying ancient Earth: systems paleobiology

A decade ago, the emerging field of systems biology was seen as a major shift in the approach to studying life; zooming out from a focus on smaller and smaller building blocks of biology to scrutinizing the whole vast, interlocking system. More recently, scientists appropriated the concept to the study of how drugs interact with biology, calling the new field systems pharmacology. Now, those who study the ancient Earth and its environment and inhabitants want in.

Andrew Knoll, a professor of earth and planetary sciences at Harvard University, wrote a part-essay, part-manifesto for the 125th anniversary of the Geological Society of America, calling for a rethinking of the way those who study the evolution of ancient life and the Earth think about their fields. He called his essay “Systems paleobiology.”

Knoll concedes the title was a bit tongue-in-cheek, since the “systems” label has been a trendy one in science lately. But the idea, he insists, is utterly serious and could provide scientists the framework to delve more deeply into evolution and understand whether life could have existed elsewhere in the solar system.

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What does the “systems” label really mean? Biologists, empowered by the discovery of DNA, had for decades been working out the function of genes. But as the field matured, Knoll noted, they realized that it would be important to understand the context—the network of interactions between genes and proteins that give rise to organisms or disease.

“Over the past decade, the earth sciences have traveled a comparable path, recognizing that the physical Earth and the biological Earth are not separate entities but rather interacting components of an integrated Earth system,” Knoll wrote in his essay. “Indeed, environmental history provides a necessary framework for understanding the history of life.”

Paleontologists often narrowly focused on the structure of the specimens, Knoll said. But physiology—the study of how living things function—could be integrated with geology, the fossil record, and even atmospheric chemistry, to understand ancient life and the ancient Earth in context. In an e-mail, Knoll explained that scientists could, by looking at fossils of leaves, “reconstruct aspects of climate and atmospheric history,” by modeling the flow of water vapor and carbon dioxide through leaves like the ones preserved in fossils. Geologists, he wrote, could come up with many “kill mechanisms” to explain a mass extinction 252 million years ago. But to narrow those possibilities, the physiological effects on organisms are key, and the fossil record squares with the idea that carbon dioxide rapidly increased.

On other planets, Knoll goes on to argue, a “systems astropaleobiology” approach might help evaluate the viability of life on Mars. Just because there is evidence of water on Mars, for example, that doesn’t mean that life would have been viable. He drives home that point with a quote from Samuel Taylor Coleridge’s “The Rime of the Ancient Mariner,” in which the water is too salty to quench the thirst of a sailor: “Water, water every where, Nor any drop to drink.” That's why a systems approach—one that looks at what might have been dissolved in the water and the tolerance life on Earth has for such conditions—might be informative.

Science has been taking increasing notice of the “systems” that shape how the world behaves, acknowledging that studying biology in isolation can be limited. It remains to be seen whether it’s possible to tease apart all the complexity of the whole system in a meaningful way that will help cure disease, build better drugs, or understand biology.

But it’s also a perspective most of us can’t escape in our daily lives, as we log into various social networks and see displayed in our list of friends and likes how we are embedded in an environment that feeds back, informing who we are, what we are like, and what we know.

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