Life › The microbial world › Bacteria & archaea: the microbial world
Gunflint Chert microfossils
1.88 billion years old (described 1954)· Fossil or site· Microbes & cells
Well establishedStrong fossil, genetic or geological evidence.
Microscopic fossils of bacteria in 1.88-billion-year-old rock from Ontario, Canada: the first widely accepted Precambrian life.
See it on the Life map →What happened
In 1953 geologist Stanley Tyler noticed dark specks in chert, a glassy quartz rock, from the Gunflint Iron Formation on Lake Superior's north shore. With botanist Elso Barghoorn he showed in 1954 that they were cells: threads, spheres and star shapes, some resembling cyanobacteria and iron-using bacteria. Silica had seeped into the cells and preserved their outlines. Volcanic ash layers later dated the rock to about 1.88 billion years.
Why it matters
It proved that a fossil record of microbes stretched far below the Cambrian, launching the systematic search for Precambrian life.
The evidence (fossils, genes, rocks)
Thin rock slices under the microscope (Tyler and Barghoorn, Science 1954; full description 1965) and uranium-lead dating of zircon crystals from ash beds in the formation.
Still debated
Some forms, such as the umbrella-shaped Kakabekia, still have no clear modern match, and the metabolisms of many cells are only inferred.
Connections (2)
▸Gunflint Chert microfossils preserves fossils of Bacteria & archaea: the microbial worldWell established
The connection
The Gunflint Chert captured a whole community of microbes about 1.88 billion years ago. Silica-rich water seeped into cells and hardened around them, preserving filaments and spheres from shallow seas. It gave scientists their first convincing snapshot of the microbial world long before animals.
When and how
Gunflint Iron Formation, northwestern Ontario, Canada; found by Stanley Tyler in 1953 and described with Elso Barghoorn in 1954.
The evidence
The microfossils have cell walls, sizes and shapes matching living bacteria, sit within the original rock fabric, and contain organic carbon.
Debates and open questions
Fossil bacteria rarely reveal metabolism; whether some were cyanobacteria or iron-oxidizers is debated, and archaea are almost impossible to recognize as fossils.
▸Gunflint Chert microfossils filled the fossil gap that worried Charles DarwinWell established
The connection
Darwin admitted in 1859 that no fossils were known from rocks older than those holding the first animals, and called this 'a valid argument' against his views. If evolution was gradual, a long earlier history should exist. Ninety-five years later the 1.88-billion-year-old Gunflint microfossils showed that life's record did reach far deeper, as his theory required.
When and how
Darwin's On the Origin of Species, 1859; Gunflint microfossils described by Stanley Tyler and Elso Barghoorn from Ontario, Canada, in 1954.
The evidence
The worry is in Darwin's own text; Tyler and Barghoorn's 1954 Science paper and later studies documented the microfossils' cellular structure.
Debates and open questions
Darwin worried mainly about missing animal ancestors, which Gunflint did not supply; Ediacaran fossils and molecular clocks address that gap, but not fully.