Scitech | On the origin of life

Freaky Friday at the Redpath Museum

In the quest to understand the origins of life, scientists analyze components of the oldest known rocks on Earth to elucidate the chemical composition of the atmosphere, and thereby the biological life on primordial Earth. According to Boswell Wing, an assistant professor in the department of Earth and Planetary Sciences at McGill, the chemical composition of these rocks indicates that there was likely a thriving microbial biosphere on Earth as early as 4.3 billion years ago (Ga).

Wing spoke last week on October 8 to launch the Freaky Friday lecture series, which will continue on most Fridays for the remainder of the semester in the Redpath Museum auditorium. The objectives of the lecture series are to confront myth and clarify science.

Wing’s hypothesis, coupled with the fact that the Earth is just 4.5 Ga, is intriguing. It leaves just 200 million years for biological life to have spontaneously generated on Earth. This limited amount of time lends credence to the panspermia hypothesis, which suggests that life exists throughout the universe and arose on Earth as well as possibly other planets by traveling on meteorites and asteroids. Furthermore, this would exponentially increase the likelihood that larger organisms could be found on other so-called Goldilocks planets – those whose temperature is neither too hot nor too cold.

In his lecture Wing mainly sought to outline scientific speculation regarding the oldest known biological life on Earth. Although disputed by many biologists and geologists, a leading candidate for the oldest tangible evidence of life is a microfossil dated to be 3.5 Ga. This evidence is contested because many scientists believe that the microfossil is really the remnant of an abiotic hydrocarbon.

The difficulty in finding microfossils, as well as the challenge in proving they are the remains of living beings, has led scientists to pursue indirect methods to demonstrate earlier evidence of life on Earth
Methane in the presence of oxygen reacts to form the more stable products carbon dioxide and water. It is believed that if methane and oxygen freely exist in the atmosphere, they are constantly being replenished. Primary sources of the regeneration of methane and oxygen are believed to be the result of biological processes such as anaerobic digestion and photosynthesis, respectively. Wing presented evidence combining field geology and lab geochemistry to demonstrate that particular rock sediments and the presence of specific ratios of sulfur isotopes present in the ancient rocks can be explained by the presence of methane and oxygen in the atmosphere in 4.3 Ga.

During the question and answer period of the lecture, Wing addressed the inherent constraints in researching historical science. He said studying the phenomena that led to the contemporary state of Earth is like assessing the results of “an experiment performed once by a sloppy physicist and absent-minded chemist without any controls.” By this he meant that the methodology he and his peers employ is based on correlational and inferential evidence. The impossibility of replicating the formation of the Earth means that historical scientists are limited by their inability to perform experiments demonstrating causation in the scientific sense of the word.

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