Scientists have dramatically expanded the tree of life, which depicts the variety and evolution of life on Earth, to account for thousands of new microscopic life forms discovered over the past 15 years. The expanded view finally gives bacteria and Archaea their due, showing that about two-thirds of all diversity on Earth is bacterial — half bacteria that cannot be isolated and grown in the lab — while nearly one-third is Archaeal.
This is great but no way is it a tree. Readers, what would you call it?
One striking aspect of the new tree of life is that a group of bacteria described as the “candidate phyla radiation” forms a very major branch. Only recognized recently, and seemingly comprised only of bacteria with symbiotic lifestyles, the candidate phyla radiation now appears to contain around half of all bacterial evolutionary diversity.
While the relationship between Archaea and eukaryotes remains uncertain, it’s clear that “this new rendering of the tree offers a new perspective on the history of life,” Banfield said. Paper. (public access) More.
The relationship between the Archaea and eukaryotes is in fact so uncertain that prominent figures such as the late Carl Woese and Craig Venter doubt they have a common origin. Presumably, it would be just as easy (or difficult) to account for their existence without a common origin.
In the present state of uncertainty, we surely can’t rule out an orchard of life.