Re: Can a human grow flaps of skin that can act as parachutes?

I believe you are referring to this website:
 http://www.sciencenet.org.uk/database/bio/animals/mammals/primates/
b01047d.
html

There are several levels to your question, so I will try and address them 
all. First of all, humans do in fact have tails early in embryonic 
development - Fallon & Simandl (1978) wrote an article in the American 
Journal of Anatomy describing how this tail, present in early 
developmental stages, is broken down through apoptosis, programmed cell 
death, 4 to 6 weeks after conception.  But in anatomical terms, a tail is 
a very specific structure, with it's own musculature, nervous connections 
and connective tissues - it is not just a growth of skin around the 
coccyx.  Therefore, making such a growth by skin extension (see below) 
would not give you a tail, but more of a flap of skin in the right place 
for a tail. 

Living epidermis is very malleable. You can get skin to grow into many 
different shapes on a living donor.  This is the basis of many plastic 
surgical techniques, including those used in reconstruction after cancer 
or burns.  But you are usually talking about skin measured onthe scale of 
centimeters or inches.

So this sets up your "parachute" idea.  Many animals use stretched skin to 
help them glide.  The skin is stretched between structural "stringers" 
(ribs in the case of Draco volans, the malaysian flying dragon; between 
the toes inthe asian gliding tree frog Rhacophorus reinwardtii, between 
the forearms and hindlimbs in the mammalian sugar glider - Petaurus 
breviceps).  These gliding membranes are not true wings as would be 
observed in birds, bats or pterosaurs, but they do tend to give the 
organism a reasonable glide ratio.  

However, the problems of the human epidermal parachutist would be 
numerous, and all of them are based around the central aerodynamic 
concepts of lift vs  drag.  Somehow you have to generate enough lift to 
give your 50-100 kg unaerodnamic human body a decent glide ratio, i.e., 
one that will end up with you being able to land without many weeks in 
traction.  There is an excellent description of glide ratios here:
 http://www.cmnh.o
rg/dinoarch/2001Jan/msg00441.html

There have been some remarkable bits of engineering in terms of 
specialized flight gear, suits with built in "winglets" that can reduce 
the terminal velocity of a skydiver from 100+ mph to about 50 mph.  
These "birdman suits" can be seen here:
 http://www.human
flight.com/skyflying/challenge.html

However, the suit alone only slows one to a very hard, probably terminally 
hard, landing which will probably trash the human landing gear, especially 
if said landing gear happens to be your head.  

In order to make an epidermal "parachute" you would need other, more 
significant biomods, including arm extension (to increase the surface 
area) and some form of muscle modification  - humans, unlike birds, have 
solid heavy bones and have relatively low strength to weight ratios.  
You'd probably need to have bionic modifiers to increase pectoral and arm 
(and possibly leg) muscle strength to keep your "flaps" extended, not to 
mention maneuvering them so that you don't just glide in on your belly, 
head, back, or other inappropriate landing devices.  This would be 
supporting a skin membrane which would be significantly larger than the 
rest of your body.  Using hang gliders as a good model, an 80 kg (200 lb)
pilot, needs a glider with >200 sq feet lift area.  Need a lot of extra 
skin.

So short answer, it's probably not a practical way to save yourself from a 
building.  I would recommend a fire escape.  Or a hang glider.