"Progress in solving the particularly puzzling origin of feath-ers has also been hampered by what now appear to be false leads, such as the assumption that the primitive feather evolved by elongation and division of the reptilian scale, and speculations that feathers evolved for a specific function, such as flight. A lack of primitive fossil feathers hindered progress as well. For many years the earliest bird fossil has been Archaeopteryx lithographica, which lived in the late Jurassic period (about 148 million years ago). But Archaeopteryx offers no new insights on how feathers evolved, because its own feathers are nearly indistinguishable from those of today’s birds. Very recent contributions from several fields have put these traditional problems to rest. First, biologists have begun to find new evidence for the idea that developmental processes - the complex mechanisms by which an individual organism grows to its full size and form — | "Progress in solving the particularly puzzling origin of feath-ers has also been hampered by what now appear to be false leads, such as the assumption that the primitive feather evolved by elongation and division of the reptilian scale, and speculations that feathers evolved for a specific function, such as flight. A lack of primitive fossil feathers hindered progress as well. For many years the earliest bird fossil has been Archaeopteryx lithographica, which lived in the late Jurassic period (about 148 million years ago). But Archaeopteryx offers no new insights on how feathers evolved, because its own feathers are nearly indistinguishable from those of today’s birds. Very recent contributions from several fields have put these traditional problems to rest. First, biologists have begun to find new evidence for the idea that developmental processes - the complex mechanisms by which an individual organism grows to its full size and form — |