By Skip Anderson MSU News Service
BOZEMAN – A Montana State University doctoral graduate discovered fossilized microorganisms in western Montana that predate by 200 million years fossils previously believed to be the oldest complex life forms in North America.
Zach Adam’s research of the fossilized remains of a eukaryote called Tappania shows that Earth’s first complex life forms reflect an actively growing state, rather than a dormant one as scientists previously suspected. A eukaryote is an organism with complex cellular anatomy and many are capable of changing their cellular shapes into complex structures.
The findings offer clues about the development of life on Earth and may contribute to the search for life forms on other planets.
Adam, who received his Ph.D. from MSU in 2014 and is now a postdoctoral fellow at Harvard University, published his findings in the May 2017 edition of the scientific journal Geology. His research was primarily funded through a National Science Foundation Graduate Research Fellowship award that he received in 2011 while at MSU.
Adam discovered the fossilized remains of Tappania, a shape-shifting organism barely larger than the thickness of a human fingernail, in a clay outcrop near White Sulphur Springs. The site is part of a collection of rocks known as the Belt Supergroup that extends throughout much of western Montana.
The relatively sudden appearance of eukaryotes around 1.6 billion years ago marked an important turning point in the evolutionary timeline, said Adam, who conducted his research in MSU’s Department of Earth Sciences, under advisers Mark Skidmore, associate professor of geology, and David Mogk, professor of geology.
For the 2 billion or so years prior to that, life on Earth consisted solely of simple microscopic organisms, Adam said.
“Microbial life dominated our planet for 2 billion years,” he said. “Then, seemingly overnight, we had organisms show up that are complex. The appearance of eukaryotes showing up on our planet was a significant event. They eventually evolved into forms of life that dominate the planet today, from plants to trees, and from fungi to people. In other words, as far as we can tell, every organism that is complex today came from these organisms.”
In addition to marking a critical step in the evolution of life on Earth, Adam said, eukaryotes are unique in having the remarkable ability to change their shape significantly, and seemingly at will, to include bulbs and trumpet-like protuberances extending from their otherwise spherical bodies. Adam explained that having dozens of intact fossils demonstrating this variability suggests to scientists that they were in an active state of their lifecycle, rather than a dormant one, when they died.
“What we found was that it was not only capable of changing its shape, but also independently directing the growth of multiple protuberances to do so,” Adam said. “It would have an outer wall that could take on a shape while an inner wall could take on a different shape. What’s remarkable is that we’d be hard pressed today to find many organisms that could do the same, in terms of taking on these shapes simultaneously.”
Mogk and Skidmore are co-authors of Adam’s paper, “A Laurentian record of the earliest fossil eukaryotes,” along with Nick Butterfield, a professor of paleobiology from the University of Cambridge, U.K., with whom Adam developed a research collaboration while a doctoral student at MSU.
The scientists theorize the protuberances possibly helped the organisms in reproduction and/or nutrient absorption.
The published findings are based on the extensive sample set collected near White Sulphur Springs, Skidmore said.
“Rather than having three quality samples, we have 40 or 50 quality samples,” he said. “This adds depth to the research and is important to the impact of its findings.”
Adam said that MSU’s proximity to the fossil-bearing rocks helped progress his research because he was able to easily travel between the research site and the lab.
“I could go into the field, look for samples with the right kind of texture and grain size, and dissolve them back in the lab at MSU and travel back to White Sulphur Springs the next day and resample as needed,” he said.
He added that there are only four or five other known sites on Earth where the ancient organisms can be found and they are located in sparsely populated and very remote areas.
“So, if you want to study this intriguing organism, you previously had to travel to faraway places,” Adam said. “It’s helpful to find them really well preserved and to make this kind of investigation accessible to researchers in North America.”
Adam said there is application for his research to inform the upcoming Mars 2020 rover mission, which is specifically designed to look for evidence of past Martian habitability.
“Answering questions about the evolution of life on Earth can inform what to look for on Mars,” Adam said. “The people in charge of Mars 2020 have said information regarding where and how to find fossils is directly relevant to their mission decisions.”
Before coming to MSU, Adam, who is from Cashmere, Washington, earned his bachelor’s degree in Earth and space sciences, and another in aeronautics and astronautics engineering from the University of Washington. He also earned a master’s degree in aeronautics and astronautics engineering from UW.
He then worked for two years as a launch vehicle inspector for the U.S. Department of Transportation in Washington, D.C., where he was part of the regulatory division that oversaw rocket technologies and designs developed by private enterprise.