Faith claimed in the thread “Origin of new genes” that human tails
aren't much in the way of tails anyway, just a flaccid rope of skin
This is not supported by the facts. Human tails are described in the following
abstract:
A case of a tail in a 2-week-old infant is reported, and findings from a review of 33 previously reported cases of true tails and pseudotails are summarized. The true, or persistent, vestigial tail of humans arises from the most distal remnant of the embryonic tail. It contains adipose and connective tissue, central bundles of striated muscle, blood vessels, and nerves and is covered by skin. Bone, cartilage, notochord, and spinal cord are lacking. The true tail arises by retention of structures found normally in fetal development. It may be as long as 13 cm, can move and contract, and occurs twice as often in males as in females. A true tail is easily removed surgically, without residual effects. It is rarely familial.
There are rare cases where even skeletal structures are developed, as can be seen in this
case:
Case 1 . A 10-year-old Arab boy arrived at our Outpatient Department
in 1977 complaining ofpain in the coccygeal region. This had first been
noticed some years previously but had become worse and was
particularly severe when he was sitting on hard surfaces. He was fully
continent of both urine and faeces. There was no history of injury,
operation or illnesses other than those commonly occurring in
childhood.
On examination, he was seen to be a healthy, well-developed
child. Systematic examination was normal and there was no
neurological deficit. On inspection, there was no perineal abnormality
but on rectal examination the posterior bony wall was found to be
markedly flexible and passive movement, particularly of the tip,
caused the patient great discomfort.
A lateral radiograph of the lower vertebral column showed the
normal number and configuration of lumbar and sacral vertebrae but
there was a very prominent coccyx measuring 8.5 centimetres in length
and consisting of five well-developed vertebrae. Anteroposterior
radiographs of the pelvis showed a spina bifida of the first sacral
segment but an otherwise normal sacral configuration. The prominent
coccygeal vertebrae were again in evidence.
Partial excision of the coccyx was considered but not performed
because the parents believed that the symptoms were not severe
enough to warrant operation.
For creationists the human tail is the result of a mutation and not “the recurrence of a formerly expressed allele” - as Faith put it - because that would be evidence for a shared ancestor of humans and great apes.
This has interesting consequences for the creationist viewpoint.
For one this implies that benefical mutations should be quite common. Only in this century there are several documented cases where humans where born with a moveable tail containing connective tissue, nerves, blood vessels and muscles. In three cases tails containing vertebrae have been reported.
On the other hand one would conclude that macroevolution understood as the development of new and complex biological structures has been observed in humans.
-Bernd
™ Version 4.2