Evolution is far too complex to be explained by a few roots and branches, they claim.
In Darwin’s The Origin of Species, published in 1859, the British naturalist drew a diagram of an oak to depict how one species can evolve into many.
But not much was known about primitive life forms or genetics back then when he was only dealing with plants and animals – long before there was any real comprehension of DNA or bacteria.
Researchers say although for much of the past 150 years biology has largely concerned itself with filling in the details of the tree it is now obsolete and needs to be discarded.
Dr Eric Bapteste, an evolutionary biologist at the Pierre and Marie Curie University in Paris, said: “For a long time the holy grail was to build a tree of life. We have no evidence at all that the tree of life is a reality.”
The discovery of the structure of DNA in 1953 – whose pioneers believed it would provide proof of Darwin’s tree – opened up new vistas for evolutionary biology.
But current research is finding a far more complex scenario than Darwin could have imagined – particularly in relation to bacteria and single-celled organisms.
These simple life forms represent most of Earth’s biomass and diversity – not to mention the first two-thirds of the planet’s history.
Many of their species swap genes back and forth, or engage in gene duplication, recombination, gene loss or gene transfers from multiple sources.
Dr John Dupré, a philosopher of biology at Exeter University, said: “If there is a tree of life it’s a small irregular structure growing out of the web of life.”
More fundamentally recent research suggests the evolution of animals and plants isn’t exactly tree-like either.
Dr Dupré said: “There are problems even in that little corner.” Having uprooted the tree of unicellular life biologists are now taking their axes to the remaining branches.
Dr Bapteste said: “If you don’t have a tree of life what does it mean for evolutionary biology. At first it’s very scary – but in the past couple of years people have begun to free their minds.”
Both he and co-researcher Dr Ford Doolittle stressed that downgrading the tree of life doesn’t mean the theory of evolution is wrong just that evolution is not as tidy as we would like to believe.
Dr Doolittle, of California University, said: “We should relax a bit on this. We understand evolution pretty well it’s just it is more complex than Darwin imagined. The tree isn’t the only pattern.”
But others see the uprooting of the tree of life as the start of something bigger, reports New Scientist.
Dr Dupré said: “It’s part of a revolutionary change in biology. Our standard model of evolution is under enormous pressure. We’re clearly going to see evolution as much more about mergers and collaboration than change within isolated lineages.”
Understanding how cells evolve and mutate is incredibly important it’s helping scientists learn why some diseases are resistant to vaccines and antibiotics, and why others can evade the immune system.
It’s leading to environmental solutions too some bacterial genes can break down harsh contaminants such as benzene into harmless by-products.
Dr Rose said: “The tree of life is being politely buried – we all know that. What’s less accepted is our whole fundamental view of biology needs to change.”
He says biology is vastly more complex than we thought and facing up to this complexity will be as scary as the conceptual upheavals physicists had to take on board in the early 20th century.
Dr Bapteste said: “The tree of life was useful. It helped us to understand evolution was real. But now we know more about evolution it’s time to move on.”
Darwin’s model is no stranger to controversy. It has played a key role in the much larger debate with creationists who are convinced life on Earth is so complex it could only have come about from intelligent design – in other words, the hand of God.
Last Update: 04 Feb 2009
Source: Daily Telegraph