In search of Earth’s earliest life forms

In October 1977, American palaeontologist Elso S. Barghoorn announced the discovery of microscopic fossils. Dated to be 3.4 billion years old, this discovery pushed back the age of the oldest known evidence of life further. Join A.S.Ganesh as he tells you more about Barghoorn and his search for the earliest life forms…

October 23, 2022 12:46 am | Updated February 24, 2023 11:47 am IST

Precambrian life form models at the Museum of Man and Nature (Museum Mensch und Natur) in Munich, Germany. 

Precambrian life form models at the Museum of Man and Nature (Museum Mensch und Natur) in Munich, Germany.  | Photo Credit: Photo: Ghedoghedo / Wikimedia Commons

Do you know what Precambrian refers to? A unit of geologic time, it corresponds to the earliest part of Earth’s history. It is named so because it extends from about 4.6 billion years ago, the point at which the planet began to form, up until the Cambrian Period, which is 541 million years ago. The Cambrian gets its name from Cambria, the Latinised name for Wales, where most of the rocks from this age were first studied.

Even till the 1950s, scientists didn’t have fossil evidence of Precambrian life forms. In the decades that followed, however, a number of discoveries pushed back the Precambrian record back in time farther and farther. American palaeontologist Elso Sterrenberg Barghoorn was among those responsible for making that happen.

Barghoorn’s background

Born in New York City in 1915, Barghoorn was not only a fine student, but also an excellent sprinter. After completing his undergraduate degree at Miami University of Ohio in 1937 with majors in botany and chemistry, he entered graduate school at Harvard University.

Barghoorn obtained his Masters in 1938 and Ph.D. in 1941 and went on to teach botany at Amherst College. When serving as a field service consultant of the U.S. Army during World War II, he was sent to Panama to investigate military equipment that was impaired by fungi. On his return from Panama in 1946, he accepted an appointment at Harvard, where he went on to become the Fisher Professor of Natural History.

Teams up with Tyler

It was in the 1950s that Barghoorn teamed up with Stanley Tyler, a mineralogist who was performing geologic investigations of the Gunflint Iron Formation in Michigan. When Tyler chanced upon ancient coal deposits that contained something like microscopic plants, he took it to MIT geology chairman Robert Rakes Shrock. After noting that the “plants” looked like fungus, Shrock suggested Tyler seek out Barghoorn, the young Harvard botanist.

In their search, they used a diamond saw to cut off slices of rock so thin that light could pass through them. Taking back slices to Harvard that he considered most promising, Barghoorn observed them under a microscope.

He realised that what he was seeing “were organisms that looked exactly like fossil algae". Working tirelessly to prove what they had, Tyler and Barghoorn published their discovery in 1954 of fossils of microorganisms. With a carefully determined age of 2 billion years, these specimens pushed back the records of life form by several times in one shot.

In the years that followed, Barghoorn attracted some of the brightest minds into his diversified research programme. His students, who themselves went on to hold distinguished academic positions, included J. William Schopf, Stanley Awramik, Andrew Knoll, Paul Strother, and many others. Working with this group, Barghoorn studied rock specimens obtained from the Nonesuch (Michigan), Bitter Springs (Australia), and Figtree (South Africa), pushing back the time of the origin of life to 3.4 billion years ago.

Figtree’s secrets

The discovery of microscopic single-cell creatures that were 3.4 billion years old was announced by Barghoorn and Knoll (presently the Fisher Professor of Natural History) in 1977. The cells were found when very thin slices of chert (hard, fine-grained sedimentary rock) from the Figtree site in the Swaziland System was examined under the microscope. What was more remarkable about this discovery was the fact that the cells were found in various stages of cell division.

While Barghoorn and Knoll announced their findings in the Science issue dated October 28, the news of their discovery had started creating a buzz earlier. An article titled “Paleontology Rebirth” that used this discovery as a peg appeared in The Washington Post on October 3, while The New York Times carried an article titled “Earliest Life Forms Are Found in Rocks” on October 24, days after the issue of Science was out on the stands.

The age of these fossils were determined precisely using radiometric dating, the same radioactive methods that were used at the time to find the age of moon rocks returned by the Apollo missions. Speaking of which, Barghoorn also served as an advisor to NASA, assisting in the development of plans for the solar system’s biological exploration, in addition to conducting microscopic examinations on lunar samples.

Aged 68, Barghoorn died peacefully in his sleep in January 1984. While he will be best remembered for extending the knowledge of the fossil record of life by nearly 3 billion years, equally important was the way in which he inspired and instilled values in his students, whom he informed and listened to, without making requests or demands.

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