A two-billion-year-old riddle of how the basic building blocks of life were formed has been solved by scientists in Ireland, it was announced yesterday.
"Nature's big bang" -- when two single cells fused into one living organism -- has been mapped for the first time by researchers led by a team from the National University of Ireland (NUI) in Maynooth.
Dr James McInerney, senior biologist, said the discovery in effect traced humans' oldest ancestor.
"This was a remarkable event, which appears to have happened only once," Dr McInerney said.
"These two primitive single cell life forms came together in an event that essentially allowed nature to grow big."
Dr McInerney said the research would help explain what gave rise to all multi-cell organisms we know today -- insects, plants, animals and humans.
Using genetics and information from the mapping of the yeast genome, evidence of two originally single cells, known as prokaryotes, were discovered in a eukaryote which formed with a nucleus.
Researchers were able to show that yeast -- a model system for molecular biology -- contained one eukaryote genome which came from two distinct different prokaryote genomes.
Dr McInerney said: "It is in the nucleus that we find the DNA of all species, and for years it had been a puzzle as to how the first nucleus was created. Now we know."
Researchers believe this can be dated to about two billion years after the oldest micro-fossils.
The discovery follows the mapping of the family tree of all nature by researchers at NUI Maynooth and comes after 10 years of research.