Why haven't we observed mutations of new body parts?

I see what I would consider evidence of body modifications today...though we wouldnt see it in mammalian, reptilian, or any other large multicelled organisms in our lifetimes...But take the case of animal that appears to have a precursor to a new body part. What do flying squirrels, sugar gliders, and certain tree snakes have in common? In the mammals, we see that they simply have a skin membrane which can be stretched out during a jump, helping to glide further...these creatures can jump from nearly any sized tree without injury, and has enough control of their membranes (and apparently, already enough instinct to know how to manipulate these membranes for a certain purpose...weave right, weave left...etc...as if their brains are being rewired along with the body). The snakes that can also "glide" do so by flattening their bodies, and they are quite proficient at it.As far as the human body goes...I myself feel that we have several organs whose uses are ambiguous at best...many like spleens, appendixes, u can easily live without whatever their contribution is to the body (spleens are much more understood these days)...However, I would say that the next thing u would notice on a human would not be more limbs...rather, the chemical/hormone producing plants in the brain and other glands will change their "recipe" long before we see that...this is just an opinion...We see what a thyroid gland does when it is either hypo' or hyper' active. We see the hypothalamus...and how its hormones contribute to the growth of humans...we see the cascades of chemicals that occur in brains while having fun or under the influence (seratonin and dopamine being directly linked to the feeling of "euphoria" or enjoying the moment). I think the biggest changes we will see in the years to come would be in the brain...we already have a few uncommon cases of people who process the optical imput of the eye in slightly different parts of the brain. And how some people who are blind DO in fact develop better usage of their other remaining senses...hearing being the most obvious. It is the most complex, amazing machine in the body...and due to its parts...and how it is directly related to our success as a species...I would venture it would continue to be the quickest changing part of the human body...And on a side note...I did once have an extra body part...an extra wisdom tooth on the upper left side..I kid u not.

I would think so. I believe the dentist referred to the case an a hyperdontial tooth. But I dont remember what the term is for a MOLAR hyperdontial tooth, they are much more rare. What are more common are Mesiodens...or an extra encisor. There is debate about where they come from. Theories include a splitting of one of the 2nd teeth...or a 3rd tooth simply developing behind the second...which in my case I would be the later, since it was by far the last tooth to erupt. U could debate either way as to if this is congenital or not. But if its a 3rd tooth developed independently of the 2nd sets...I would lean toward a slight genetic mutation...therefore congenital...but once again, its all debatable in this particular case.Edited by Franatic25, : No reason given.Edited by Franatic25, : No reason given.

I would add though that I personally had another case of DNA mutation. Of which there is very little known about its origins and causes due to its rarity (no funding goes to the few, mostly to the vast genetic mutations). In my case, I have ACC (adenoid cystic carcinoma). A very rare cancer, with interesting traits. I bring it up only because of what we DO know...it is NOT congenital...but neither is it known why it occurs, but toxicity in the lungs (tobacco, or other chemicals) has been pretty much ruled out as well. It appears to be a sudden drastic mutation of the genetic level of a single cell...People can live with it for YEARS...literally, without consequence. I apparently had it since I was 5 or 6 (their guess) but it didnt start to show until I was 13...and it wasnt diagnosed until I was 20. Its is VERY slow growing...and causes no pain.What is interesting though, is that chemotherapy, and radiotherapy have little to no effect on it. Why? Because apparently, unlike popular belief...radiation causes the most damage to a cell, and its DNA when the cell is dividing...our normal body cells (minus nervous system cells) repicate very frequently, radiation to these cells is bad news.Unlike normal cells though (and just about every other cancer) these cells replicate rarely...the cell walls acting as a protective agent to the cells dna, and other parts of the cell needed to survive....likes its own personal "ozone layer, protecting us from the suns radiation".Perhaps in the future, this could also be a trait normal cells might pick up on...slower multiplication...if the normal cells in our body dont replicate often...they are MUCH less succeptable to the dangers radiation causes to dna.(Also, already had the surgery to have it removed...but due to metastasis...it is nearly impossible for the doctors to believe that it is gone for good...and the "new" infected area would not show up for years...a potentially deadly disease...but since it takes so long to develop...not one that is a death sentence any more than old age is.)