A new research by scientists has rejected the 80-year old theory of 'primordial soup' as the origin of life, and has instead suggested that it was the Earth's chemical energy, from hydrothermal vents on the ocean floor, which kick-started early life.
"Textbooks have it that life arose from organic soup and that the first cells grew by fermenting these organics to generate energy in the form of ATP. We provide a new perspective on why that old and familiar view won't work at all," said team leader Dr Nick lane from University College London.
"We present the alternative that life arose from gases (H2, CO2, N2, and H2S) and that the energy for first life came from harnessing geochemical gradients created by mother Earth at a special kind of deep-sea hydrothermal vent - one that is riddled with tiny interconnected compartments or pores," he added.
The team focused on ideas pioneered by geochemist Michael J. Russell, on alkaline deep sea vents, which produce chemical gradients very similar to those used by almost all living organisms today - a gradient of protons over a membrane.
Early organisms likely exploited these gradients through a process called chemiosmosis, in which the proton gradient is used to drive synthesis of the universal energy currency, ATP, or simpler equivalents.
Later on, cells evolved to generate their own proton gradient by way of electron transfer from a donor to an acceptor.
The team argues that the first donor was hydrogen and the first acceptor was CO2.
"Modern living cells have inherited the same size of proton gradient, and, crucially, the same orientation - positive outside and negative inside - as the inorganic vesicles from which they arose", said co-author John Allen, a biochemist at Queen Mary, University of London.
"Thermodynamic constraints mean that chemiosmosis is strictly necessary for carbon and energy metabolism in all organisms that grow from simple chemical ingredients [autotrophy] today, and presumably the first free-living cells," said Lane.
"Here we consider how the earliest cells might have harnessed a geochemically created force and then learned to make their own," he added.
This was a vital transition, as chemiosmosis is the only mechanism by which organisms could escape from the vents.
"The reason that all organisms are chemiosmotic today is simply that they inherited it from the very time and place that the first cells evolved - and they could not have evolved without it," said Martin.