The largest study ever of bird genetics has uncovered some surprising facts about the avian evolutionary tree, U.S. researchers said on Thursday, including many that are bound to ruffle some feathers.
Falcons, for example, are not closely related to hawks and eagles, despite many similarities, while colorful hummingbirds, which flit around in the day, evolved from a drab-looking nocturnal bird called a nightjar.
And parrots and songbirds are closer cousins than once thought.
The findings challenge many assumptions about bird family relationships and suggest many biology textbooks and bird-watchers’ field guides may need to be changed.
“One of the lessons we’ve learned is appearances seem to be very deceiving,” said Sushma Reddy of Chicago’s Field Museum of Natural History, whose study appears in the journal Science.
“Things that are quite different-looking sometimes end up being related,” she said.
For the study, Reddy and colleagues studied the genetic sequences of 169 bird species in an effort to sort out family relationships in the bird family tree.
Scientists believe birds, which first appeared roughly 150 million years ago, evolved from small feathered carnivorous dinosaurs.
“Modern birds as we know them evolved really rapidly, probably within a few million years, into all of the forms we see. That happened 65 to 100 million years ago,” Reddy said in a telephone interview.
Reddy said these quick changes have made bird evolution hard to pin down, and several smaller prior studies have led to conflicting results.
“We didn’t have a good sense of how any of these major bird groups were related to each other,” said Reddy, who worked with researchers at several other labs.
“We’ve tried to represent all of the major groups of birds and all of the major lineages,” Reddy said.
Their findings suggest birds can be grouped broadly into land birds, like the sparrow; water birds, like the penguin; and shore birds, like the seagull.
But there are many paradoxes within these groupings.
For example, water-loving flamingos and some other aquatic birds did not evolve from water birds. Instead, they adapted to life on water.
And some flightless birds are grouped with birds that fly.
Reddy acknowledges the results are likely to stir debate in many circles, but she said she is confident in the findings.
“I think a good study brings up as many questions as it answers,” she said.
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John Umana // Jul 1, 2008 at 8:39 pm
The June 2008 bird genetics study of Chicago’s Field Museum of Natural History (the Early Bird Assembling the Tree-of-Life Research Project) completely re-writes the avian evolutionary tree, and is stunning in its impact. The genetics study shows that, though they look alike, for example, falcons are not closely related to hawks or eagles. Several birds that look very different, including woodpeckers, hawks, owls and hornbills, are all closely related to perching birds. Flamingos, tropicbirds and grebes, all of which are closely related, did not evolve from water birds. Contrary to conventional wisdom, daytime hummingbirds evolved from drab nocturnal nightjars. Tropicbirds (white, swift-flying ocean birds) are not closely related to pelicans or other waterbirds. But perching birds, on the one hand, and parrots and falcons on the other, which do not look all that much alike, in fact descend from a recent common ancestor. Shorebirds are not a basal evolutionary group, which refutes the established view that all modern birds evolved from shorebirds. It is an understatement that appearances are deceiving. Birds that look or act similar are not necessarily related. Modern birds evolved relatively rapidly within a few million years during an explosive radiation, sometime between 65 million and 100 million years ago. The same is true of flower evolution. One day there are no flowers in the fossil record, and the next ‘day’ there are flowers, as Charles Darwin observed. Likewise, flowers that look alike are frequently not closely related. So how does this genome-scale phylogenetic evidence on avian evolution possibly jive with Darwinian gradualism, incremental changes over millions of years? It does not and cannot. Something else is going on to explain this planet’s remarkable biodiversity. The best hope to answer these questions is more and better science, not reliance on rote 19th century conjecture. Whatever the causative mechanism for bird or other biological evolution, what we’re finding is not ‘natural selection’ at work here.
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