This specimen was once thought to represent the earliest life on Earth.By Alan O’Connor
In the National Museum of Ireland’s acquisition register, the entry for specimen NMING:F582 reads:
“Eozoon canadense; presented by Sir J.W. Dawson; Petite Nation, Canada; Archaen; One polished.”
The specimens seen in Fig. 1 is one of many specimens of Eozoön canadense recovered from Canada. It is a rock with stripes that suggested to 19th century scientists that it could have an organic origin and be the oldest evidence for life on Earth.
The Eozoön canadense controversy
Discovered in the 1850s, Eozoön canadense was announced in 1865 as the fossilised remains of a foraminifer (The Foraminifera are a group of single-celled animals still alive today). The concentric layering visible in Fig. 1 were thought to represent the infilled chambers of the animal’s shell. Its discovery in rock previously thought to be absent of all evidence of life (today known to be approximately 1 billion years old), made it famous as the earliest evidence of life on Earth. Eozoön canadense means ‘Canadian dawn animal.’
In 1866, however, two Galway-based scientists, William King (1809-86) and Thomas Rowney (1817-94) published a paper which politely disputed Eozoön’s organic origin. Their studies had brought them to the conclusion that the specimen’s features were better explained by comparison with similar structures of inorganic origin. Such examples, they said, could be found in the Connemara ophite (also known as Connemara marble).
Thus began, over the next few decades, a series of exchanges in the scientific literature between proponents of an organic origin (Eozoonists), and those who saw only lifeless mineralisation in each specimen. At times, the exchanges took a more personal flavour, including accusations of ‘defective observation,’ and ‘complete misapprehension.’ At one point, an Eozoonist remarked to an opponent that he did not ‘feel called upon to expend valuable time in giving …the instruction which he requires to qualify him for discussing this question." On another occasion, a journal editor felt he could not circulate one particular letter as it contained the ‘kind of criticism we are quite unwilling to publish.’
By the end of the 19th century, reasoning in favour of Eozoön’s inorganic origin was accepted by the majority of the scientific community. Today, Eozoön is considered to be a pseudo-fossil: a feature in rock which resembles the remains of a once living organism, but is in fact of inorganic origin. Pseudo means ‘false’.
Although the supposed discovery of fossils in rocks of such age was remarkable at the time, we now know that life is even older than that. In Australia, preserved films of blue-green algae have been dated to 3.4 billion years. The earliest evidence of multicellular life is known from 900 million year-old rock, and fossils become reasonably common only in rocks less than 600 million years old.
How did this specimen come to be in the museum?
The specimen was given to the museum by the Canadian geologist Sir John Dawson (1820-99). It was Sir John who named Eozoön, and he died an unreconstructed Eozoonist. His story recalls the aphorism of physicist Max Planck (1858-1947), that “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
This particular specimen is part of the museum’s scientific collection, and is not on public display. However, representatives of the most ancient Irish fossil can be seen on the museum’s ground floor, in cabinet DE-226, in a window case near the entrance to the museum. Oldhamia is a trace fossil from Bray Head, representing an unknown creature. A trace fossil is an indicator of activity, rather than the preserved remains of the organism itself. The fossils are approximately 500 million years old.
The information for this article was taken from the following sources:
Allaby, Michael (2010), Oxford Dictionary of Ecology, 4th edition. Oxford University Press.
Eyles, Nick and Miall, Andrew (2007). Canada Rocks: The Geologic Journey. Fitzhenry and Whiteside Limited.
Knowles, Elizabeth (Editor) (2009). Oxford Dictionary of Quotations, 7th edition. Oxford University Press.
O’Brien, Charles F. (1970). Eozoön canadense “The Dawn Animal of Canada,” Isis, Vol. 61, No. 2, pp. 206-33.
Rothery, David A. (2010). Geology – The Key Ideas. CPI Group, U.K.