You are here From W. Ford Doolittle (2000) "Uprooting the tree
of life." Scientific American, 282(2):90-5. Note that distances
are not necessarily to scale in this image. This image reflects
a view held by some practicing scientists (including Dr.
Doolittle, the author of the original article) that there was a
period in life's early history when genes swapped so frequently
that it is impossible to treat those earlier lineages as truly
distinct, nor to trace those lineages back cleanly to a single
ancestor. They do not dispute that life has some common
ancestor, but they do seek to clarify how we talk about that
ancestor.