Sagittal Crests in Humans?
I know that gorillas have to have sagittal crests to attach the jaw muscles. But why do humans not need them?
- Anonymous1 decade agoFavorite Answer
I do not pretend to know anything about sagittal crests, but I found this which seems to be a reasonable explanation.
A sagittal crest is a bony ridge running lengthwise across the middle of the top of the skull from front to back. The sagittal crest indicates the presence of strong jaw muscles as the muscles that enable chewing are anchored to the sagittal crest. It can then be said that the larger the crest, the more powerful the jaws. Paranthropus in some cases had massive sagittal crests to go along with massive molar teeth. This allowed them to chew the toughest of foods. Female Paranthropus also had sagittal crests. Having a sagittal crest would cause the head to look pointed or conical. As such Paranthropus species would have had a conical shape to the top of their head.... Homo erectus, on the other hand, did not have a sagittal crest with the exception of a few Asian fossils. Rather than having a sagittal crest Homo erectus had a sagittal keel. A sagittal keel is a thickening of the bone that runs lengthwise across the top of the skull in a similar position as the sagittal crest. A sagittal keel would not produce a conical shape to the top of the head as they did not protrude far enough to form a noticeable feature.http://www.cryptozoology.com/blog/blog.php?id=1842
Most Homo sapiens lost them likely as part of the general trend toward thinning of the cranial bones during the Pleistocene, to make room for larger brains. However there is a very small portion of modern humans who have this, but we do not know why they do. Patrick Stewart of Star Trek is a good example of a modern human (Homo sapiens sapiens) that has this feature.
I would also point out that gorillas and humans do not share a common ancestor, whereas chimpanzees, whom also do not have a saggital crest, do share a common ancestor with humans.
- Anonymous4 years ago
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The sagittal crest is the ridge at the top of the skull. It goes from the top of the forehead to the back of the head along the top. The nuchal crest is the ridge at the back of the skull, just above the neck. You may be able to feel your own nuchal crest is you feel just above your hairline. It is more prominent on males though. Both of these crests are responsible as places for muscles to attach to and a larger crest would mean the muscles were larger there. The muscles attached to the sagittal crest were connected to the jaw and helped in chewing tough foods. We don't eat as tough foods today and so a modern human has a very small sagittal crest if any. The nuchal crest is attached to muscles that hold the head upright.
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- Anonymous7 years ago
"I would also point out that gorillas and humans do not share a common ancestor, whereas chimpanzees, whom also do not have a saggital crest, do share a common ancestor with humans." Not true. All apes share a common ancestor, as do all primates, all mammals... and indeed all life on earth does. Chimpanzees are indeed our closest relatives, that is the species with whom our common ancestor is most recent. Unless of course god created the earth after the divergence of gorillas and humans/chimps but before the divergence of humans and chimps.
- Anonymous4 years ago
The sagittal crest runs along the top of the head and the nuchal runs transverse along the back. Two entirely different crests with different orientations and muscle attachments and, therefore, functions.