The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the U.S., and the third largest in the world, next to those in New Zealand. New research suggests that rather than beginning in the ocean, cellular life originated in hot springs such as this.
Credit: Wikimedia
VANCOUVER: The origins of cellular life may not have sprung from oceans, but from steaming inland geothermal ponds, say scientists.
Until now, scientists have been fixed on marine environments as the originators of the earliest life forms, but new analysis has revealed that the chemical composition of modern cells is closely matched with the vapour vented by geothermal fields.
The researchers, publishing in a recent issue of Proceedings of the National Academy of Sciences, said that based on the internal composition of cells, the most likely environment for the origin of life would have been similar to the surface activity found in Yellowstone National Park in the U.S. or Iceland's geothermal springs, with a proximity to vapour vents that channel matter from the Earth's core.
The proposition that life on Earth began in terrestrial settings and subsequently invaded the sea directly challenges the popular belief that modern life originated in the ocean, and is conceptually similar to Darwin's theory of evolution.
"Our model and its further development will hopefully help us better understand the properties of modern cellular systems," said lead author Armen Mulkidjanian from Osnabruck University in Germany. "Indeed, [to quote Ukrainian evolutionary biologist Thomas Dobzhansky] 'Nothing in biology makes sense, except in the light of evolution'."
Figuring out composition
Mulkidjanian's team were keen to uncover the reasons behind the universal prevalence of potassium (K+) ions over sodium (Na+) ions in the cytoplasm of all living cells. This inorganic content imbalance was what led them to further investigate possible areas of origin outside of marine existence.
"We examined a variety of environments in search of natural habitats with high levels of transition metals and phosphorus compounds, as well as a K+/Na+ ratio. The problem was that Na+ is far more abundant in the sea and in most terrestrial habitats," said Mulkidjanian.
"We looked all over the place for the conditions and processes that would lead to K+ enrichment. The only environments that satisfied these criteria were the vapour-dominated zones of inland geothermal fields. Numerous fumaroles and mud pots overlaying a vapour-dominated zone make a geothermal field. The emissions from the inland geothermal zones are specifically enriched in K+, and the ionic composition of the sea was not conducive to the origin of the first cells."
Origin of life theory
Aditya Chopra from the Australian National University's Planetary Science Institute in Canberra agreed with the paper's findings, commenting, "It is difficult to choose one candidate as the most likely environment for the origin of life, particularly because it is difficult to know exactly the nature of the environment 4 billion years ago by studying analogues on the present day Earth."
While Mulkidjanian's findings are sure to raise flags in certain areas of accepted origin of life theory, Chopra warned against over-excitement. "Because of the large uncertainties both in the composition of the environment and life forms, such analysis is not sufficient to argue the case of a land-based geothermal site over any other hydrothermal environment. Unfortunately, better data is not available to the authors but this paper is a step in the right direction," she said. "The ideas in this paper will nevertheless help astrobiologists consider the possibility and the nature of the origin of life on other planets such as Mars and moons of Jupiter and Saturn."
Mulkidjanian's findings do happen to be on par with the often-contentious premise supported by Darwin's theory of evolution. An 1871 letter from Charles Darwin to English botanist Joseph Hooker first mentions the "warm little pond" vision, saying "But if (and Oh! What a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity etc., present that a protein compound was chemically formed ready to undergo still more complex changes."
Earth
This offers a new and insightful perspective on the origins of life. We are currently studying the analysis of early life on Earth, and this article is very interesting. It is helpful to broaden our scope of knowledge with new information that challenges the mind to think about such visionary ideas.