How have some animals evolved wings?

When learning about evolution, someone might wonder about how irreducibly complex parts of animals, such as wings, have evolved.  A wing only works when there is an entire functioning wing. So this brings up the question, how does an animal without wings evolve into an animal with wings? The most reasonable explanation would be that wings began evolving with a slightly different purpose. 

Theropods that lived in the trees would get around by jumping from branch to branch. If they missed the jump, they could fall out of the tree and die. These theropods evolved into birds. According to discovermagazine.com, birds and theropods both "Have three bones that appear to have evolved from the digits on a common five-fingered ancestor." A theropod with a small flap of skin between its fingers would have a slightly larger surface area when jumping between branches and that would decrease the chance of it falling. Through generations, that skin flap became larger and eventually evolved into a functioning wing where the animal could flap it's wings and fly away.

If I were to do further research, I would want to look into birds that don't fly, like penguins or emus. If they can't fly, what is the purpose of having wings?

Sources:

http://blogs.discovermagazine.com/80beats/2009/06/18/how-dinosaur-feet-evolved-into-bird-wings-new-fossil-provides-clues/

The Blind Watchmaker by Richard Dawkins

The evolutionary paths concerning vegetarianism seem to be less a matter of biology as they are an issue of cultural ideals.  Physically, humans have the internal organs, systems and other mechanisms for meat consumption.  However, it has become a growing trend in society to opt out.  Some people today choose not to eat meat because they are morally against mass-market animal slaughter.  Others do it because it goes against religious values or simply because they believe it to be a healthier life choice.  However, it’s hard to go back and pinpoint one specific turning point that “began” vegetarianism. 

            Back in the day (talking thousands of years,) people got sustenance through “hunting and gathering.”  This required a fairly nomadic lifestyle, traveling around to wherever the food source went.  By this process, early man spread across the continents.  The food that was eaten was not always about choice, but more about availability.  If meat was scarce, then less was eaten.  However, it is unlikely that people lived a fully vegetarian lifestyle. 

            Many scientific researchers agree that humanity would not have developed as it did without a meat-laden diet.  According to N. A. Barnicot, “It is virtually certain that diet, as a major component of the human environment, must have exerted evolutionary effects, but researchers still have little good evidence.”  Meat and animal products do contain vital proteins and nutrients humans need, especially fats for brain growth.  Many believe that this is the primary reason our brains grew to what they are today.  Scientists have additionally stated that our teeth would not have formed the way they are if humans were not meant to tear through meat. 

Though it is disputed that animal-product nutrients can be found elsewhere, meat is often the “best” source.  According to Dr. Stephen Byrnes, “Vegetarianism and veganism are neither natural nor healthy diets…and it is not primarily meat-eating which is responsible for the spread of cancers and heart disease.” There is cause for concern with vegans, who are often malnourished in essential vitamins and minerals such as B12 and iron.  People need these to survive and develop, and it is usually not recommended for children to be vegan.  Some argue that the same goes for vegetarianism.    

            Whether or not someone believes vegetarianism is the right step, the idea developed in society as a choice.  Once people learned how to farm and grow their own food, they had more options.  As agriculture grew, so did population size, and with it religion.  Today, vegetarianism is still highly connected with religious values, especially in Buddhism, Jainism and devout Hinduism.  According to Daniel Lazare, “Vegetarianism is most fundamentally about the importance of not taking life other than under the most extreme circumstances.”

            This is not to say someone can’t be a perfectly healthy vegetarian.  In fact, Einstein said, "Nothing will benefit human health and increase chances for survival of life on Earth as much as the evolution to a vegetarian diet."  I just wouldn’t choose it for myself.  The convenience of modern supplements has made it easier to make the switch in a healthier fashion.  However I’d argue that if there suddenly were no more animal products, humanity would be weakened.  Even if I’m wrong and it isn’t evolutionarily disadvantageous to not eat meat, I don’t think it’s advantageous either. 

http://www.diet-and-health.net/Diet/veg_diet.html

http://www.biblelife.org/abrams2.htm

http://www.theecologist.info/page14.html

http://berkeley.edu/news/media/releases/99legacy/6-14-1999a.html

Barnicot, N. A. "Human Nutrition: Evolutionary Perspectives." Integrative Physiological & Behavioral Science 40.2 (2005): 114-117. Advanced Placement Source. EBSCO. Web. 9 Nov. 2010.

http://web.ebscohost.com/ehost/detail?vid=8&hid=105&sid=097bc83a-1caf-42ca-ac7c-7ad011a0e422%40sessionmgr112&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aqh&AN=24225923#db=aqh&AN=24225923

LAZARE, DANIEL. "My Beef With Vegetarianism." Nation 284.5 (2007): 25-29. Advanced Placement Source. EBSCO. Web. 9 Nov. 2010.

http://web.ebscohost.com/ehost/detail?vid=4&hid=105&sid=097bc83a-1caf-42ca-ac7c-7ad011a0e422%40sessionmgr112&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aqh&AN=23749985