Go ahead and punch me in the face for being such a dweeb, but seeing Terrence Mallick’s Tree of Life really did have a fairly profound effect on my relationship with Mother Nature. It was apparent pretty much from the moment I walked out of the theater; something about the director’s vision just put me a bit more in tune with the natural world--especially, for some reason, birds. It’s kind of like the arrow in the FedEx logo: Once you start paying attention to birds, you can’t stop seeing them. But unlike the shipping company’s satisfying but straightforward visual gag, birds reward your attention over time with their incredible diversity. This graphic shows how all those dazzling species came to be.
The chart was created in conjunction with a groundbreaking new paper outlining avian evolution, published recently by an international team of biologists in the journal Nature. Using fossil records and DNA data, the group traced the speciation of all 9,993 species of birds known to man in unprecedented detail. Essentially, the dense circle you’re looking at is one of the most epic family trees ever created. Dr. Gavin Thomas, a postdoctoral fellow at the University of Sheffield, in England, was responsible for making the graphic, so I turned to him for a little help in decoding it.
You can think of the radial display like a typical top-down family tree, just wrapped up like a burrito to fit in as much data as possible. Each gray, concentric ring, Thomas explained, represents an interval of 20 million years, so the ancestor found in the circle’s center is roughly 110 million years old.
The colors correspond to the rate of speciation: Red indicates a high rate, green is moderate, and dark blue shows species that were slowest to mutate. Look at the Paleognaths at roughly 3 o’clock; they have a "fairly direct path to the centre," Dr. Thomas points out, meaning there are "relatively few speciation events" separating the 100-million-year-old birds from the ones living today. Among other species, the Paleognath superorder includes ostriches, which seem like a not-so-distant relative of dinosaurs, so that all checks out. Just below that you’ll find cardinals, conebills, and tanagers, all of which, in contrast, are products of far more significant speciation.
The team’s exhaustive work has already yielded some surprising insights. Whereas it was generally thought that biodiversity, in recent history, was slowing down across the board, speciation in birds is actually speeding up. Dr. Arne Mooers, a biologist from Simon Fraser University in Canada and one of the paper’s co-authors, speculated about the phenomenon in a statement. "Perhaps birds are special," he says. "Maybe they’re so good at getting around they can escape local competition from relatives and start anew elsewhere, producing bursts of new species at different times and in different parts of the globe."
It seems like a reasonable theory. Now can’t we get a bit closer the bull’s-eye to see where the dinos fit into all this?
[Hat tip: Yale News]