Los Angeles, CA - None of us might be here if it weren't for the ancient fusing of two microscopic, single-celled organisms called prokaryotes, NASA-funded research has found.
Molecular biologists at Los Angeles' Center for Astrobiology compared proteins present in more than 3,000 different prokaryotes, a type of single-celled organism without a nucleus.
They showed that two major classes of relatively simple microbes fused together more than 2.5 billion years ago, indicating a new pathway for the evolution of life on Earth.
This endosymbiosis, or merging of two cells, allowed a highly stable and successful organism to evolve, able to use energy from sunlight via photosynthesis.
As these double membrane prokaryotes evolved, one type, called cyanobacteria, became the primary oxygen-producers on the planet, generating enough oxygen to alter the chemical composition of the atmosphere and set the stage for the evolution of more complex organisms such as animals and plants.
"Higher life would not have happened without this event," said researcher James A Lake. "These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth's atmosphere. Humans could not live. No oxygen-breathing organisms could live."
"This work is a major advance in our understanding of how a group of organisms came to be that learned to harness the sun and then effected the greatest environmental change Earth has ever seen, in this case with beneficial results," said Carl Pilcher, director of the NASA Astrobiology Institute.
A full report appears in Nature.