
Source: David M. Hillis, Derrick Zwickl, and Robin Gutell, University of Texas
In my previous post I mentioned “Pale Blue Dot,” a photograph taken by Voyager 1 from the outer reaches of the solar system showing Earth as a barely visible dot of light. But even on Earth, we humans are just one in a family of millions.
Brett Keller discusses in his blog Brett Keller & the World a remarkable “tree of life” published a few years ago in the prestigious journal Science. This “tree,” arranged in a circular format, was developed by David Hillis and colleagues at the University of Texas. They selected around three thousand species, trying to include representatives from all major groups. You may read more about it and see where our species, Homo sapiens, fits in at Mr. Keller’s blog.

Possible phylogenetic tree
These representations, more formally called phylogenetic trees, are intended to illustrate the evolutionary relationships between species. Lines are drawn from two species (call them A and B) that are closely related, meeting at a vertex called a “node” representing the most recent species that is ancestral to the both of them. Another node may occur further up, representing the most recent common ancestor of the A-B ancestor and species C, and lines will be drawn to both of those. And perhaps even further up is the ancestor to species A, B, C, and D, with one line going to the A-B-C ancestor and one going to species D.
Continue reading “Family Circle” →