Origins of Flight and
Evolutionary Adaptation
by Gay Noeth
Winter 2003
Two Theories :: From the Ground :: From the Trees :: Finch Beak Adaptation :: Embryonic Beak Development
Origins of Flight?There has long been the debate of how dinosaurs may have evolved into birds of flight. What behavior actually led up to it? Did it then become a matter of Natural Selection as Darwin suggests, where the use of the wings was more useful and thus these prehistoric animals were more readily able to survive and pass on their genes to the next generation?
Two Theories
One theory suggests flight evolved by gliding from tree to tree and then
learning to flap during the glide, while the other theory suggests they
learned to fly by increasing their running speed while flapping, and
eventually taking off from the ground.
Recently, this debate has been rekindled.
According to an article by the Associated Press, the head of the
biological flight laboratory at the University of Montana, Kenneth P
Dial, has made a connection between the way young birds use their wings to help them run quickly before they are able to fly and how two-legged feathered dinosaurs might have done the same thing on their way to developing flight.
In order to achieve this understanding, Mr. Dial observed the habits of
juvenile birds like partridges and pheasants, which share some physical
similarities with feathered dinosaurs. These similarities include large
powerful legs with weak undeveloped wings.
Mr. Dial set up differing inclines for the young chicks to traverse and
observed that the steeper the incline the more use was put to the
undeveloped wings. Dial decided the flapping was for traction, much like
the use of spoilers on a race car. Dial believes dinosaurs may have used
their primitive wings in the same way to escape predators, developing
and strengthening the muscle, until flight was finally attained.
For more information, read the entire article here:
http://www.msnbc.com/news/860259.asp
And in another article by the Associated Press, the discovery in the
Chinese province of Liaoning, of fossilized remains of an animal that
had two sets of feathered wings (forelimbs and hind legs) has brought
back the gliding theory.
The animal, known as Microraptor gui, is described by Paleontologist
Xing Xu of the Institute of Vertebrate Paleontology at the Chinese
Academy of Sciences, as being 2 1/2 feet long with leg feathers arranged in a pattern similar to wing feathers in our modern day birds. "They are long, and some have asymmetrical vanes like flight feathers"
Was gliding an intermediate step to flight in the history of evolution? Read the entire article here
http://www.msnbc.com/news/862757.asp
From dinasaurs we move to modern days and look at another case of where Darwin's ideas of evolution, his Theory of Natural Selection plays out before us.
Peter and Rosemary Grant (ecologists) began spending annual time in the Galapago's, on a 100-acre island called Daphne Major, in 1973. They were there to watch Finch's struggle to survive during different climatic
changes. With climate change would come food changes.
During a long drought beginning in 1977, the finch's with the smaller beaks, beaks appropriate for eating small seeds, found their food source dried up and gone and they perished. The finch's that had slightly larger beaks were able to feed on larger, harder seeds. They survived. Within a few generations of finches, the Grants were able to see that the average beak size increased 4% over the previous normal beak size of the ground finch.
In 1983, when the rains returned and once again, small seeds were
abundant, they witnessed again, a transformation. The finches with the
smaller beaks were once again able to feed copiously and hence, reproduce and pass on their genes for smaller beaks.
The Grants were also able to document a similar incident involving the
beak of the cactus finch, and the natural hybridization that went along
with a climatic change requiring blunter beaks.
You can read about the Grants at their research at
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html
or for those more scientifically inclined, you can read some of Peter
Grants abstracts about their research at
http://www.eeb.princeton.edu/FACULTY/Grant_P/PRG_Abstracts.pdf
Beaks were again in the news recently, but for a totally different
matter. While we may not all agree on animal experiments to further human science, it is interesting to note a current experiment being
undertaken.
Recently, Jill Helms and colleague Richard Schneider of the University
of California at San Francisco, delved into the mystery of beaks. Helms, an orthopedics researcher, is hoping their experiment may help
better understand why and how things like cleft palate and craniofacial birth defects occur.
By using duck and quail embryos, Helms and Schneider removed the cells
which seemed to give rise to beaks and switched them to the other bird. After further incubation, they rechecked the eggs and found that the duck was now growing the quails beak and vice versa.
They both hope that by understanding what causes a beak to develop the way it does could in turn, shed light on human development.
To read more about this interesting experiment see the Associated Press full story http://www.msnbc.com/news/863332.asp