Earliest Life Research by ODU's Noffke Reviewed in Prestigious Journal, Nature
The journal Nature published on Thursday, March 6, a review highlighting the latest research on Earth's earliest life by Old Dominion University geobiologist Nora Noffke. The article, which appears in the magazine's News & Views section, is titled "Modern life in ancient mats" and is accompanied by photos of 3 billion-year-old rocks that Noffke discovered in eastern South Africa.
Noffke found the sandstones close to the village of Nhlazatse, South Africa. They contain spectacularly preserved geological structures that hold clues about the microbes believed to have been the planet's first life forms.
Her research shows that microbially induced sedimentary structures (MISS), a term that her research has helped to coin, are very reliable biosignatures, contributing significantly to the information provided by other geobiological evidence in dating earliest life.
The Nature article, written by Michael M. Tice of Texas A&M University, focuses on three structures among Noffke's find that "seem to point particularly conclusively to an overlying microbial mat" that existed nearly 3 billion years ago. "(The) find significantly augments the record of such structures from the Archaean eon," the author states.
Revelations about the Nhlazatse discoveries were published originally in a special January 2008 issue of the journal Geobiology, providing some of the sturdiest evidence yet that life forms had colonized sandy coasts of Earth by the time of the Archean Age, which ended 2.5 billion years ago.
Noffke's discoveries over the past decade have helped to answer questions scientists have long grappled with: Which microbes were the earliest living organisms, and where in the geological record can we possibly find irrefutable evidence of the existence of such tiny life forms? She says most likely cyanobacteria-photoautotrophic and oxygen-producing microbes-had colonized some sandy coasts by 3 billion years ago and, amazingly, that they still can be found on coastal shorelines today.
The latest research on rocks in South Africa has turned up a virtual treasure trove of geological samples supporting her case that the microbial mats we see today covering tidal flats also were present as life was beginning on Earth. The mats, which are woven of cyanobacteria, can cause unusual sedimentary structures in the sand beneath them. Along today's beaches near ODU in Virginia and North Carolina, Noffke has identified two dozen such structures caused by present-day microbial mats, and she has found corresponding formations in rocks dating back through the ages. The latest findings are the oldest known-and the best preserved-examples.
Two co-authors of the Geobiology article are ODU graduate student Dina Bower and Don Swift, Slover Professor in ODU's Department of Ocean, Earth and Atmospheric Sciences. Other authors are Nic Beukes, a geology professor at the University of Johannesburg in South Africa, and Robert Hazen, renowned mineralogist at the Carnegie Institution's Geophysical Laboratory in Washington, D.C.
Noffke's research has opened a new window in the understanding of the rise of life. Although it seems certain that early life on Earth involved microbes, scientists have found it difficult to turn up evidence of organisms that lived many millions of years ago and were only a few millionths of a meter long. Until now, only the filigrane fossils of smallest bacteria found in glass-like flintstone or the "stromatolites," which are domes formed by early photoautotrophic microorganisms, seemed to constitute an archive for the investigation of early life.
However, a new group of fossils, the MISS, are now helping to decipher life during the Archean time period (2.5 - 3.9 billion years BP).
The work of geochemists and paleobiologists has produced evidence suggesting that life was
present on Earth perhaps as early as 3.8 billion years ago. Nevertheless, the evidence can be disputed-and often is both by scientists and creationists-particularly because fossil evidence can be mimicked by purely physical processes. For example, carbon believed to have organic origins can in fact be inorganic.
Noffke argues in her latest article that her MISS samples, which she says definitely contain traces of organic material in the 3 billion-years-old rocks, are more reliable than stromatolites in establishing when life started. She also predicts that geobiological methods may someday help decide whether there has been life on other planets.
The Nature article, which expands upon discoveries by Noffke that also were noted in the May 5, 2006, edition of Science magazine, can be found on the Web at http://www.nature.com/nature/journal/v452/n7183/full/452040a.html. The author, Tice, suggests more research to identify conclusively the microbes that produced the MISS. "Noffke and colleagues' observations help fill in the geological record of microbial communities and ecosystems at a potentially critical stage in their evolution," he writes. "They tell us that microbes were constructing cohesive mats in early tidal environments much as they do today. But what this means in detail for the physiology and behavior of the organisms involved is an open question, and one that awaits future studies of the mechanisms of mat construction in both aerobic and anaerobic environments."
NORA NOFFKE BACKGROUND
The research of Old Dominion University geobiologist Nora Noffke comprises a decade of adventures in Germany, France, South Africa and the United States, and it illustrates the debt that scientific advancement owes to creativity, adaptability and tenacity of purpose.
The flurry of recognition she has enjoyed recently is based on a hypothesis that is, at best, tangential to her early work in science. Hers is a story of a geologist who becomes fascinated with the felt-like microbial mats, which are living weaves of tiny organisms, or microbes. These mats can be found today blanketing sandy tidal flats in many coastal areas worldwide. Noffke has discovered the mats just 30 miles from the ODU campus, near the northern terminus of the Chesapeake Bay Bridge-Tunnel.
In her early education at the University of Tubingen, Germany, Noffke's geological focus was on macroorganisms-or larger critters-that made traces in sands and muds, later preserved as trace fossils in rock.
Her doctoral study at the University of Oldenburg, Germany, however, veered off toward the
relatively new discipline of geomicrobiology. Her Ph.D. adviser, W.E. Krumbein, was "one of the first microbiologists studying the interaction between bacteria and sediment or bacteria and rock," Noffke said.
Doing fieldwork for her Ph.D. on the sandy tidal flats along the North Sea, Noffke observed microbial mats constructed by cyanobacteria, the same organisms that Krumbein's and others' research linked to stromatolites dating to the Archean Age.
"I thought that if living cyanos are abundant in the modern sandy tidal flats, they
must do something in the sediment, such as make traces, and if they make traces, those structures might become preserved," she explained.
To understand her research, the layman should first know how a living microbial mat can affect a sandy tidal flat. One example is the stabilization of loose sand grains by a microbial mat. A microbial mat is coherent like a carpet, and cannot be torn by routine movements of water. Therefore, the sand underneath a microbial mat cannot be disturbed. But where there is a rip or hole in the mat, the exposed sand can become transported away by water rushing over it. Specific morphologies-forms or patterns-can result on the tidal surface.
For her doctoral thesis, Noffke documented 21 fresh structures (microbial traces) on tidal flats of the North Sea. She speculated that similar structures that are very old might be preserved in tidal sandstone. Her first paper on the subject was published in 1996.
The next step was to find evidence of the structures in petrified tidal flats. Noffke went to the south of France, to the Montagne Noire near Montpellier, where geological evidence indicates tidal flats existed a few hundred million years ago.
She had enough funds for a four-day search, but by late on the fourth day she had found nothing in the old rock that resembled the microbial mat-related structures she documented by the North Sea. Then, in the evening, with the light of the setting sun at a steep angle illuminating the rocks, she discovered a slab of rock with a ripple pattern that looked precisely right. "I saw the ripples in a sudden moment and shouted, 'Yes, that's them!'" she said.
Her revelations, published in 2000, came out simultaneously with similar findings of a research group at the University of Southern California. Noffke had not known that the group had been investigating the same hypothesis. Together, the two published reports spawned a new term for science: "microbially induced sedimentary structures."
Noffke did not rest on her accomplishment. She wanted to survey a region with sandstone that is older than that in the Montagne Noire. During postdoctoral research as guest of Harvard University geology professor A.H. Knoll, she visited the 600-million-year-old Nama Group in Namibia, Africa. Shortly after joining ODU in 2002, she launched a 10-day expedition to the Pongola region of South Africa. This time, as her script seemed to dictate, she found no samples until the 10th day.
"We had several hundred square miles to survey for a structure that might be just a few square inches in size. We had 10 days' time, but no luck until on the last day. At 4 p.m., without much hope left, I decided to just take a last look at some exposed rocks near a lake. And here we found a rock with a wrinkle structure, just about 3 x 8 inches wide."
(Her latest discoveries near Nhlazatse were on a return visit to the Pongola region in 2006.)
The offshoot of her 2002 find was a 2003 article in the journal Geology that placed cyanobacteria potentially back as far as 2.9 billion years.
A fortuitous meeting between Noffke, Virginia Tech geologist Kenneth Eriksson and paleobiologist Ed Simpson from Kutztown University led to Noffke's next expedition to South Africa in 2004, this one to the Barberton greenstone belt near Swaziland. Eriksson is not an expert in microbially induced sedimentary structures, but once he became familiar with Noffke's research, he knew just where to look for the structures.
A variety of geological clues can pinpoint where ancient, sandy tidal flats existed. Eriksson, who has taken many research trips to South Africa, was able to identify a relatively compact search area in the Barberton belt, and on this expedition the researchers were able to find samples right away. These were the samples dated to 3.2 billion years ago, and which led to the April 2006 article in Geology and the May 2006 "Editor's Choice" news article in Science magazine.
The Science article called Noffke's latest discovery of fossil microbial mats "direct evidence" that life evolved on Earth during the Early Archean Age. It added, "Analysis of the carbon isotope compositions of the laminations further supports their bacteria origin. Concentration of these features at the top of sedimentary sequences formed in shallow water environments suggests that the microbes in the mats may have derived their energy through photosynthesis."
In the April paper in Geology, Noffke noted that the oxygen content of the atmosphere prior to 3 billion years ago is not known. It may have been very low. "Photosynthesis of the ancient microbial mats inferred in this study may have been nonoxygenic," the paper explained, "but if microbial communities of this type were oxygenic, then for hundreds of millions of years, such photosynthetic systems may have provided a steady, yet rapidly consumed source of oxygen-a source that would gradually come to dominate the atmospheric chemistry of Earth."
Noffke knows some will question her findings. But she said she and her co-workers have lined up five levels of proof, showing, for example, that the petrified structures she has identified in rocks are found only where ancient tidal flats existed. The structures exactly match those in modern sandy tidal flats produced by microbial mats.
She also has proof from the carbon isotope tests to show that the carbon in her samples is organic, as well as proof from thin sections of the ancient structures in which the bacterial filaments of the microbial mats can be seen.
Noffke's research earned the 2007 James Lee Wilson Award of the Society of Sedimentary Geologists, which is given annually to recognize international excellence in marine geology by a young scientist, and the Honor Fellow Membership of the 15,000 member large Geological Society of America.
(Contact Jim Raper, Old Dominion University, 757-683-5585 and jraper@odu.edu)