The team found that the cellular machinery needed to create mitochondria was constructed from parts pre-existing in the bacterium. These parts did other jobs for the bacterium, and were cobbled together by evolution to do something new and more exciting.
"Our research has crystallized with work from other researchers around the world to show how this transformation happened very early on – that the eukaryotes were spawned by integrating the bacterium as a part of themselves. This process jump-started the evolution of complex life much more rapidly than was previously thought," said co-author Trevor Lithgow
The research consisted of two components, the first used computers to read, compare and understand DNA sequences. From this, experiments were designed to do actual laboratory testing using a bacterium that is the closest living relative to the original ancestor of the mitochondria.
The latest findings were only made possible due to a gradual gathering of evidence within the scientific community and recent developments in genome sequencing. "We can now "read" with great care and insight genome sequences - the complete DNA sequence of any organism. From these sequences we find tell-tale clues to the past. Our findings are relevant to all species, including the evolution of humans," Professor Lithgow said.
"It continues to amaze that this theory, proposed in the century before the advent of molecular investigations, is so accurate on a molecular scale. This improved understanding is directly relevant to the big picture timeline for the evolution of life."
The researchers say their findings will be regarded by some scientists as controversial as many have long-held views on the process of evolution as a tinkerer. "This will surprise and may even spark debate. However our research compliments the basic rules of life. Even at the molecular level, the rules of the game are the same. Evolution drives biology to more and more complex forms," Professor Lithgow said.
Citation: Felicity Alcock, Abigail Clements, Chaille Webb, Trevor Lithgow, 'Evolution: Tinkering Inside the Organelle', Science, February 2010, 327(5966), 649 - 650; doi: 10.1126/science.1182129