In the first place, many mammals have a high degree of genetic similarity (Spetner, Not by Chance, page 69). For example, the cytochrome C of a dog is about 90 percent similar to that of a human, and the hemoglobin of a horse is about 88 percent similar to that of a human. In view of this, a 98 percent genetic similarity between apes and humans is not surprising. It is interesting that some sources put the difference between humans and apes much higher, as high as 10 percent. At least for one gene, human and chimpanzee alleles seem to differ by 13 base pairs out of 270, for a difference of about 5 percent. (See Science, 6 Jan. 1995, pp. 35-36.)
There are also some notable differences, apparently. Mammals in general can drink and breathe at the same time, according to a posting on talk.origins. But humans cannot. This is the price we pay for being able to speak. It would seem that this must involve quite a bit of genetic difference from the apes.
The following quotation from ReMine, The Biotic Message, page 449, calls into question the significance of DNA similarity:
It should also be noted that chimpanzees have 24 pairs of chromosomes and humans have 23 pairs, so there is a definite discontinuity.
There are two species of flies (Drosophila) that look alike but have only 25 percent of their DNA sequences in common. Yet the DNA of humans and chimpanzees share 97.5 percent. This means the DNA of two virtually identical flies is 30 times more different than that betweens humans and chimpanzees.
Many of the similarities between humans and apes derive simply from the structural similarity of their skeletons. Given any animal that is partially upright, with grasping hands on its forelimbs, there may just be one optimal way to design the rest of the organs. For example, such an animal will need extra intelligence to control its hands. It will also tend to be flexible and adaptible, and not so tied to the seasons as other animals are; thus it is more reasonable to have a reproductive cycle that permits offspring at any time of year, rather than only at certain seasons. Thus much of the genetic similarity may simply be a result of structural similarity.
This does complicate the fossil picture, however. The similarities of the skeletons, combined with the various races of man and the various species of apes, can make the evolutionary task of determining ancestry very confusing. Add to this the fact that one does not always have a complete skeleton, but only a few bones, or fragments of bones. Furthermore, what makes humans unique is not the structure of our skeleton but intangibles such as language, culture, and thought, which are very difficult to infer from the fossil record. Even if these differences arise from one or two percent of the genome, this is a very significant one or two percent.
And in fact, there appears to be a notable division between the skeletons of apes and humans. Glenn C. Conroy of Washington University in St. Louis reported in the journal Science in June, 1998 that "Mr. Ples," the name given for the fossil of an Australopithecus africanus, a hominid that lived in what is now South Africa, had the brain capacity of about 515 cubic centimeters. Another A. africanus skull had a brain capacity of 370 cc. Modern humans have a brain size of about 1,350 cc., while 370 cc is the size of a chimpanzee brain.
There is also a striking division in speech ability between humans and apes in the fossil record. The following information is taken from a news item:
Without accepting the time scales given in this announcement, the information about speech abilities is still worthy of note.
A report published in April, 1998 in the Proceedings of the National Academy of Sciences states that scientists at Duke University have explored a new avenue of fossil anatomy and found surprising evidence suggesting that the Neanderthals, relatives of modern humans, could have had the same gift for speech as modern man. The research was conducted by Dr. Richard F. Kay and Dr. Matt Cartmill at the Duke Medical Center in Durham, N.C., with the assistance of a former student, Michelle Balow. The Duke scientists directed their research at the hypoglossal canal in all primates. It is a hole at the bottom of the skull in the back, where the spinal cord connects to the brain.
Through the canal run nerve fibers from the brain to the muscles of the tongue. On the basis of comparative measurements of hypoglossal canals of modern humans, apes and several human ancestor fossils, the researchers concluded that the canals of modern humans are almost twice as large as those of modern apes -- the chimpanzee and the gorilla -- which are incapable of speech. They also found that the canal size of austrolopithecines, earlier human relatives that died out about one million years ago, did not differ significantly from that of chimpanzees. To narrow the range, the scientists examined skeletons of Neanderthals and also of species of the Homo genus that lived as much as 400,000 years ago. These included Kabwe specimens from Africa and Swanscombe fossils from Europe. Their hypoglossal canals fell within the range of those of modern Homo sapiens."By the time we get to the Kabwe, about 400,000 years ago, you get a canal that's a modern size," Cartmill said. "And that's true of all later Homo species, including Neanderthal."
Another recent study of Neanderthals, from The New York Times, December 1, 1998, Tuesday, Science Desk section, "Neanderthal Or Cretin? A Debate Over Iodine," by John Noble Wilford, suggests that the neanderthals were modern humans with an iodine-deficient diet. Iodine deficiency produces features remarkably similar to those observed in Neanderthal remains.
An article from Creation in the Crossfire, a creationist publication, of November 1998, states "The human ear has three main parts to it and the inner part of the ear has a canal that determines location in space and time. The shape of the inner ear canal is related to the form of locomotion. When the australopithecines were examined, it was shown that they did not have the right kind of inner ear canal for bipedality." (The australopithecines are another purported link between humans and other primates.)
In real life, there is no problem distinguishing between humans and apes. I have never seen a gorilla that I would confuse with a human, or vice versa, despite the unusual appearances of various rare individuals. I never heard of a gorilla or a chimpanzee escaping from the zoo and disguising itself as a human for several months before it was found out and returned to captivity. Even if an ape should evolve to a human stature with an ape brain, it would be far from a human being. If we saw the creatures from which fossils arose in real life, we might have very little difficulty knowing whether they were humans or apes, but the scarcity of evidence leaves plenty of room for interpretation.
One can understand in evolutionary terms why there should be animals such as apes that are so close to humans. But why would God create a creature that is so close to a human, but not quite? To answer this, we have to reason from what we know or can infer about God's motives in the creation. This may lead us to considerations that seem far removed from those that are expected in this context. The original creation was intended to contribute to the happiness of man and animal. We can assume that in many cases the Lord created animals that would be a delight to man, and created man to be a blessing to the animals. Even today, both children and adults enjoy seeing gorillas and chimpanzees in zoos. It is reasonable to assume that these creatures were partly made for just this reason, to be a joy and entertainment to us. In a similar way, we can speculate in unorthodox terms that an animal such as the koala bear was created because of its cuddly appearance, which is a delight to children and many adults. Even if such creatures don't seem well adapted from our viewpoint, they serve their purposes very well.
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