I don't know about vestigial organs, but here's something I found interesting:
Its from the book 'The Greatest Show on Earth' by Richard Dawkins:
The vas deferens is the pipe that carries sperm from the testis to the penis. The most direct
route is the fictitious one shown on the left-hand side of the diagram opposite. The actual route taken by
the vas deferens is shown on the right of the diagram. It takes a ridiculous detour around the ureter, the
pipe that carries urine from the kidney to the bladder. If this were designed, nobody could seriously deny
that the designer had made a bad error. But, just as with the recurrent laryngeal nerve, all becomes clear
when we look at evolutionary history. The likely original position of the testes is shown in dotted lines.
When, in the evolution of mammals, the testes descended to their present position in the scrotum (for
reasons that are unclear, but are often thought to be associated with temperature), the vas deferens
unfortunately got hooked the wrong way over the ureter. Rather than reroute the pipe, as any sensible
engineer would have done, evolution simply kept on lengthening it – once again, the marginal cost of
each slight increase in length of detour would have been small. Yet again, it is a beautiful example of an
initial mistake compensated for in a post hoc fashion, rather than being properly corrected back on the
drawing board. Examples like this must surely undermine the position of those who hanker after
‘intelligent design’.
