Our Featheredfriendosaurs?
by Bradley Kemp
The
widely held idea that modern birds are the evolutionary descendants
of dinosaurs is an old one, first formally proposed by the naturalist
Thomas Huxley in the 1860s. It's an appealing idea, too, one that gives
dino fans the thrill of mingling with dino kin at their backyard bird
feeder. But like most stories, it may or may not be true.
The debate rages in many forums
- from journals like Science to shopping-mall displays of dinosaur
fossils. It's even a hot contest on the University of Kansas campus,
where Larry Martin, the KU Natural History Museum's curator of vertebrate
fossils, is one of the leading doubters, while his colleague, Richard
Prum, curator of birds and an international authority on the evolutionary
development of feathers, champions the prevailing view.
The debate Prum and Martin carry
on today was touched off by the discovery in 1861 of Archaeopteryx,
a 150-million-year-old fossil bird that bore both feathers and reptilian
features, such as teeth and a bony tail. New fuel was added to the fire
in the mid 1960s, when the German entomologist Willy Hennig introduced
a new way of puzzling out evolutionary relationships - what scientists
call phylogenies -- among species.
Hennig's tool was called cladistics.
Before Hennig, scientists had tried to determine relationships among
species based on all their features. Wrong, Hennig said. Because
all species change over time (that's the essence of evolution), the
characteristics that are different between species don't reveal
anything about evolutionary relationships.
It's only the shared characteristics,
Hennig said, that matter. And modern birds may share dozens of novel
characteristics with theropods, the group of dinosaurs thought to have
given rise to birds.
