Friday, May 23, 2014

Understanding the Evolution of Flightless Birds

Source: National Geographic News Report 5/13/14

One of the stronger evidences for evolution is the existence of such creatures as flightless birds.  If one were creating creatures willy-nilly all at once, as creationists assert, why create a creature with wings and feathers but without the ability to fly?  It makes no sense from a creationist perspective, but it makes perfect sense in an evolutionary perspective. 

Scientists, however, are always interested in the details of evolution.  Where does each known creature, past or present, fit in the evolution of life?  This article focuses on a puzzle that evolutionary biologists have been pondering for 150 years: where to place the creatures known as tinamous, a South American bird that has limited ability to fly.  It shares some similarities with flightless birds such as emus, ostriches, and kiwis.  Did it evolve from creatures like these, redeveloping the ability to fly?  Such a scenario is unlikely.  But it is equally unlikely that they would independently evolve other similar features to the flightless birds, known collectively as ratites.

In the past, such questions could not be answered conclusively because the evidence of morphology (body features of existing creatures) and fossil evidence can only suggest possible avenues of evolution.  The ability to sequence DNA now provides an independent means of analyzing ancestry and a new study has done just that with the DNA of flightless birds and the tinamous.

Science advances using the scientific method.  This method tests a hypothesis by stipulating what results would be expected in an experiment if the hypothesis were true.  Then if the tests show the expected results, it supports the hypothesis.  Results that are at odds with what is expected cast doubt on the hypothesis.

This study produced evidence from DNA that supports the hypothesis that the flightless birds and tinamous share a common ancestor that could fly.  The fact that DNA evidence allows us to confirm a connection suggested by morphology and fossils adds to the existing mountain of evidence that evolution is a fact, not a hypothesis still being tested, as anti-evolution critics would have us believe.


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