Some hold with the theory that the development of an embryo
shows the stages of evolution. In other words, what first
develops is fishlike, and then like a small mammal, and then
like a lemur or ape, and then something we would recognize as
human. Very early embryos have what look like little gill slits
in the beginning of their development. At about four weeks,
embryos have a little tail. At around six to twelve weeks, the
white blood cells dissolve the tail, and the fetus develops into
an average, tail-less baby... most of the time, at least. Every
now and again, we get a little extra bit of baby, in the form of
a vestigial tail. Not all things that look like tails -
protrusions from the tailbone - actually are what doctors
consider "true" tails. There are a number of growths or cysts
that can form right on the tip of the tailbone. Some of the more
unpleasant options are large tumors, elongation of the existing
vertebrae, and even parasitic twin tissue. (A parasitic twin is
not a fully-formed twin, but the