How did the earliest forms of life evolve?

Underwater heat vents. Image: US National Oceanic and Atmospheric Administration.

A NEW study led by ANU sheds light on how the earliest forms of life evolved on Earth about four billion years ago.

In a major advance on previous work, the study found a compound commonly used in hair bleach, hydrogen peroxide, made the eventual emergence of life possible.

Lead researcher associate Prof Rowena Ball from ANU says hydrogen peroxide is the vital ingredient in rock pores around underwater heat vents that set a sequence of chemical reactions leading to the first forms of life.

“The origin of life is one of the hardest problems in all of science, but it is also one of the most important,” says Dr Ball.

The research team made a model using hydrogen peroxide and porous rock that simulates the dynamic, messy environment hosting the origin of life.

“Hydrogen peroxide played multiple roles in the emergence of living systems, and this study investigated how it ensured the randomly fluctuating temperatures and pH levels necessary to energise the production of a chemical world that made life on Earth possible,” Dr Ball says.

“Our simulations reveal the importance of long rock pores or lengthy, interconnected porous structures in enabling the creation of long, large molecules.”

The research advances upon previous studies by modelling the flow of reactive species through porous rock rather than through a single pore.

Dr Ball says the high temperature fluctuations must not rise too high or occur too often.

“The system needs to spend enough time at higher temperatures to carry out essential synthetic reactions, but not so much that the reactants are totally consumed or destroyed. We call this the ‘Goldilocks’ distribution,” she says.

“This effectively gives us the ‘fundamental equation of life’. It says that for life to begin and persist, the habitat must exhibit a specific range of temperature fluctuations.”

This result provides new and valuable guidelines in the search for extraterrestrial life.

Hydrogen peroxide also promotes the evolution of enzymes called catalases that prevents a second “origin of life” event.

“The ubiquitous presence of life, and hence catalases, in all habitable environments prevent hydrogen peroxide from accumulating sufficiently anywhere to drive a second origin event,” Dr Ball says.

“Evolution can be thought of as burning a succession of small bridges. But the first cellular life destroyed probably one of the most important bridges, the one that spanned the living and non-living molecular worlds.

“Any chance of rebuilding that bridge was permanently rubbed out by the persistence of catalases throughout subsequent evolution.”

The study is published in the international journal “Royal Society Open Science”. Dr Ball co-authored the research paper with Prof John Brindley from the University of Leeds in the United Kingdom.

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