New Theory On Origin of Birds: Enlarged Skeletal Muscles \t\t\t \t\t\t \t\t\t\tScienceDaily (July 2, 2011) - A developmental biologist at New York Medical College is proposing a new theory of the origin of birds, which traditionally has been thought to be driven by the evolution of flight. Instead, Stuart A. Newman, Ph.D., credits the emergence of enlarged skeletal muscles as the basis for their upright two-leggedness, which led to the opportunity for other adaptive changes like flying or swimming. And it is all based on the loss of a gene that is critical to the ability of other warm-blooded animals to generate heat for survival. Dr. Newman, a professor of cell biology and anatomy, studies the diversity of life and how it got that way. His research has always centered on bird development, though this current study, "Thermogenesis, muscle hyperplasia, and the origin of birds," also draws from paleontology, genetics, and the physiology of fat. Dr. Newman draws on earlier work from his laboratory that provided evidence for the loss, in the common dinosaur ancestors of birds and lizards, of the gene for uncoupling protein-1 (UCP1). The product of this gene is essential for the ability of "brown fat," tissue that protects newborns of mammals from hypothermia, to generate heat. In birds, heat generation is mainly a function of skeletal muscles. "Unlike the scenario in which the evolution of flight is the driving force for the origin of birds, the muscle expansion theory does not require functionally operative intermediates in the transition to flight, swimming, or winglessness, nor does it require that all modern flightless birds, such as ostriches and penguins, had flying ancestors. It does suggest that the extinction of non-avian dinosaurs may have been related to a failure to evolve compensatory heat-generating mechanisms in face of the loss of UCP1," says the scientist
I'll have to find the original research paper and read it, but one thing I'm a little confused about, and it may stem from a misunderstanding... what about the mammals? They still had UCP1 correct? Yet were able to survive the climate change associated with the K-T extinction event. But the avian theropods who had lost this gene gained an advantage from this. Wouldn't the mammals have the same disadvantage as the other non-avian dinosaurs? Also, how early did this muscular expansion occur? If it occurred as early as the first ceolurosaurians or maniraptoriformes then why did they not also survive the extinction? If this adaptation happened later, such as after the deinonychosauria split off, so that only true birds received it, then flight would have preceded it. At least non-powered flight in species such as Microraptor and possibly powered flight with the emergence of the first paraves. Sorry if this doesn't make much sense, my little sister is yelling in my ear. Really interesting though.
great find... plausible but like was said before id have to read the full article... really gets you thinking about the various paths of evolution that lead to present day and how they came to be
mammals have our own unique way of surving cold climates. birds fly south, because they can. mammles hybernate. ps. im not much on my history, but didnt the continents move to where they are slowly over time? so mammles might have developed hair and other heat protections slowly as their continents moved away from the equater.