Since Charles Darwin published the theory of evolution by means of natural selection in 1859, myths and misinterpretations have eroded public understanding of his ideas. For example, some people continue to argue that evolution isn't a valid scientific theory because it can't be tested. This, of course, isn't true. Scientists have successfully run numerous laboratory tests that support the major tenets of evolution. And field scientists have been able to use the fossil record to answer important questions about natural selection and how organisms change over time.
Still, the evolution-is-not-falsifiable myth remains popular. So does this one: The second law of thermodynamics, which says an orderly system will always become disorderly, makes evolution impossible. This myth reflects a general misunderstanding of entropy, the term used by physicists to describe randomness or disorder. The second law does state that the total entropy of a closed system can't decrease, but it does allow parts of a system to become more orderly as long as other parts becomes less so. In other words, evolution and the second law of thermodynamics can live together in harmony.
One of the most persistent myths, however, concerns the relationship of humans to great apes, a group of primates that includes the gorilla, orangutan and chimpanzee. Someone who believes the myth will say, "If evolution exists, then humans must be descended directly from apes. Apes must have changed, step by step, into humans." This same person will often follow up with this observation: "If apes 'turned into' humans, then apes should no longer exist." Although there are several ways to attack this assertion, the bottom-line rebuttal is simple -- humans didn't descend from apes. That's not to say humans and apes aren't related, but the relationship can't be traced backward along a direct line of descent, one form morphing into another. It must be traced along two independent lines, far back into time until the two lines merge.
The intersection of the two lines represents something special, what biologists refer to as a common ancestor. This apelike ancestor, which probably lived 5 to 11 million years ago in Africa, gave rise to two distinct lineages, one resulting in hominids -- humanlike species -- and the other resulting in the great ape species living today. Or, to use a family tree analogy, the common ancestor occupied a trunk, which then divided into two branches. Hominids developed along one branch, while the great ape species developed along another branch.
What did this common ancestor look like? Although the fossil record has been stingy with answers, it seems logical that the animal would have possessed features of both humans and apes. In 2007, Japanese scientists believe they found the jawbone and teeth of just such an animal. By studying the size and shape of the teeth, they determined that the ape was gorilla-sized and had an appetite for hard nuts and seeds. They named it Nakalipithecus nakayamai and calculated its age to be 10 million years old. That puts the ape in the right place on the time line. More important, the scientists found the ancient bones in the Samburu Hills of northern Kenya. That puts N. nakayamai in the right geographic place, along a trajectory of hominid evolution that stretches for several hundred miles in eastern Africa. The Middle Awash region of Ethiopia lies to the north, where the African continent dead-ends into the Red Sea.