Evolution in Action 2

Feeding a Growing Population

Genetically modified organisms (GMOs) are becoming more and more common, especially in the form of genetically engineered plants for food. Genetic engineering can make food crops drought-, disease-, herbicide-, and pesticide-resistant; make them have higher yields; make them stay fresher longer, and many other benefits. Genetically modified crops have helped meet the needs of a growing global population.

However, many worry that GMOs will lead to the evolution of pesticide-resistant insects and herbicide-resistant "superweeds." Genetic drift from the modified organisms may cause similar modifications in coexisting species. Some are also concerned about the potential effects of GMOs on human genetic makeup.

Artificial selection is nothing new; humans have been controlling reproduction of plants and animals to create the best possible crops and livestock almost since the development of agriculture. Some see GMOs as simply the next level of artificial selection, while others see it as a potentially dangerous tool with uncertain outcomes.

Useless Appendages

Vestigial limbs or organs are physical structures that exist despite being useless in performing any specific functions. These structures were once necessary for survival, but have since become unnecessary through evolutionary processes.

Vestigial structures are strong evidence for evolution because they help prove common ancestry between species. Species with similar vestigial structures probably have a common ancestor. Vestigial structures also demonstrate the effects of macroevolution, or evolution over a very long period of time, because it takes a long, long time for a structure to evolve from usefulness to uselessness.

Pythons and boa constrictors have tiny leg bones near their tail ends. Humans have tail bones and wisdom teeth. Some fish living in completely dark caves have eyes. Flightless birds, such as ostriches, have wings. All of these represent vestigial limbs or organs.