Life on earth isn't a battlefield
The search for the origins of life is a challenge, to say the least. But we have some clues. We know that the Earth formed about 4.5 billion years ago and that for the first several hundred thousand years it was too hot for any carbon-based life form. And we know that all living organisms today descended from a single living cell arising some 3.5 billion years ago. “The window for life beginning is quite small in geological terms – somewhere between a quarter and half a million years,” says Powner.
The “where” may also prove important. Some believe those fissures or “hydrothermal vents” at the bottom of the oceans (the Lost City Hydrothermal Field, for example, lies in the mid-Atlantic ocean, 2,600ft under the ocean’s surface) hold the key. According to Dr Nick Lane, leader of the UCL Research Frontiers Origins of Life programme, certain warm alkaline vents, rich in hydrogen and other minerals, are naturally electrically charged, and this could explain how cells began to generate energy. They do this through creating charged membranes that drive the chemical reaction between hydrogen and carbon dioxide. “All cells, from bacteria to human, have membranes which are charged,” explains Lane, author of e Vital Question: Why is Life the Way it Is?. “It’s amazingly strong. If you look at the electrical charge you would experience if you were the size of a molecule, it’s equivalent to a bolt of lightning.” Clues exist, but Lane, whose work on Chemiosmosis and the Foundations of Complex Life is funded by a UCL Provost’s Venture Research Fellowship award, admits the search for the origins of life is “the black hole at the heart of biology”.
Back in the 1970s, a new kind of simple celled organism was discovered, known as archaea. Many inhabit extreme environments such as ocean vents, but they can also be found in dental plaque. It is now clear that all complex cells, like those of animals, plants and fungi, originated from an archaeon engulfing a bacterium around one billion years ago. The echoes of this event are still present in our DNA. The bacteria eventually became mitochondria, the cellular powerplant. The search is on for the archaea from which all complex life evolved and a recent candidate is looking good – an organism called Lokiarchaeota has genes that make many of the important proteins found in our cells. “It looks really like our sister group,” says Professor Buzz Baum, Professor of Cell Biology at the MRC Laboratory for Molecular Cell Biology at UCL.
From an evolutionary standpoint, we think of life as “survival of the fittest”. But recent research suggests that actually a spirit of co-operation may be at the heart of the first complex cell. Baum recently published a paper on just how archaea and bacteria could have come together – the archaea, he says, rather than engulfing the bacteria, began co-operating, eventually merging into one cell with a new membrane. “Darwinian evolution is about survival of the fittest – two deer fight, the strongest gets the mate,” he says. “But the biggest transitions in life on Earth came from different cells working together. You shouldn’t see life as a battle field – it’s many things living together.” It’s a comforting thought that our cells might have evolved through co-operation, not conflict.