12 | LEHIGH ALUMNI BULLETIN FINDING LIFE IN ROCKS Growing up near Reading, Pennsylvania, Andrew Knoll collected fossils and read books on archaeology as a boy, learning “there is all sorts of interesting history beneath our feet, if you just know where to look for it.” At Lehigh, he was equally inspired by biology and geology, putting them together one night in a dorm-room epiphany. “I remember sitting there thinking, maybe these aren’t two separate universes they seem to be,” Knoll says. He turned to the nascent field of geobiology, looking at sedimentary fossils that hid microscopic fossils deep within them. As a graduate student at Harvard, he did fieldwork in South Africa, helping uncover evidence of the earliest microbial life 3.5 billion years ago, when the young Earth had an inhospitable atmosphere of ammonia and methane. Frustrated by the difficulty in establishing that timeline in a structured way, he changed tack when he got his first teaching job at Oberlin. He decided to look at the Precambrian era, right before animals began to appear, and work backwards. That’s what brought him to Spitsbergen, where he used techniques looking at the decay of chemical isotopes over time to determine the precise age of fossils within the rocks. By examining relative percentages of carbon isotopes, he was able to deduce the fluctuation of carbon in organic matter and seawater to create a unique chart that could constrain dating of fossils. “It looked like a cardiac patient—it went way up and way down,” he says. “It played a major role in helping establish the carbon cycle of the Earth over time.” Later, with colleagues, he used uranium isotopes to pin down the beginning of the burst of species known as the Cambrian Explosion to 540 million years ago, showing how it was preceded by a buildup of oxygen and phosphorus in the environment that allowed life-forms to flourish. By contrast, he was among the first to show how a buildup of carbon dioxide due to volcanic activity during the Permian period around 252 million years ago led to the third mass extinction in which 90 percent of oceanic species and 70 percent of land species vanished. Among other accolades, Knoll received the 2022 Crafoord Prize in Geosciences, a complement to the Nobel Prize, for the “fundamental contributions to our understanding of the first 3 billion years of life on Earth and life’s interactions with the physical environment through time.” His work not only sheds light on ancient mysteries, but also offers insights into our own era, when carbon is once again building in our atmosphere due to man-made pollution. “What we see at the end of the Permian period is really a distant mirror on the 21st century,” says Knoll, who contributed to a recent U.N. global report on climate change. Over the years, he’s also worked to educate the public with appearances on the PBS science program “NOVA,” and the book “A Brief History of Earth,” a synopsis of how the Earth has changed over 4 billion years. “Many geologists think hard about how knowing something about the past may help us understand the future,” he says. “I want to try and help the public understand the changes we are seeing, and how investing in solutions now will be far better in the long run than doing nothing.” HUMANS’ IMPACT ON THE LAND Daniel Richter investigates the way that the Earth is being changed by human activity in a more immediate way, looking at the soil beneath our feet. He still remembers the sweltering hot day as a graduate student at Mississippi State, when a soil professor led a field trip into a nearby forest, pulling up pine needles from the ground. “He got a big handful of soil and started talking in the most poetic way,” he remembers, “saying if you understood soil, you could understand so many other areas.” Richter was hooked, beginning a scientific career to examine the dirt and clay we take for granted. “Ninety-nine percent of the terrestrial surface has some kind of soil on it,” Richter says. And yet, as Leonardo DaVinci said 500 years ago, we still “know more about the movement of celestial bodies than about the soil underfoot.” Richter takes a multidisciplinary approach, impacted by his time at Lehigh, where he focused his time on playing soccer and pursuing a major in philosophy—a subject not unlike soil science in a way. “You look around and see all of this superficial stuff, but what’s controlling things is the invisible stuff beneath the surface,” he says. He continued his education after college, working a year at Bethlehem Steel and hiking the Appalachian Trail before following his girlfriend, now wife, Susan (Adam) Richter ’75 to Mississippi State, where he enrolled in forestry. He went on to earn his Ph.D. in soil science and ecology at Duke. After graduating, he worked at Oak Ridge National Laboratory, where he participated in debates among scientists over the impact of acid rain on soil and water. He became fascinated by how humans impact the land. “Until recently,” he says, soil science textbooks “might have had one or two references to human beings.” And yet, “like it or not, more than half of the soils on Earth are being managed or altered by humanity,” he says. Andrew Knoll ’73
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