Toshihiko Komatsu, a functional anatomist at Osaka University in Japan, found in a study of dissection results that where most humans have 2 muscles as upper arm biceps some people have 3 or even 4 bicep muscles. (triceps? quadraceps?)
However, in Komatsu's research, 14 to 20 percent of people were found to have three muscles and 1 to 4 percent were found to have four muscles in their biceps.
People with more than the usual two muscles also tended to have more muscles than normal in other parts of their body, such as their elbows or fingers.
Do some people have genetic variations that code for more muscles? Or does noise in the system cause some small fraction of developing embryos to grow extra muscles in assorted places?
If people who have extra muscles are symmetric in their muscle counts (e.g. 3 muscles on upper arms on both arms) then that tends to suggest genetic variations coding for this result.
Any time you read about people who deviate from the biological norm for some quality of their bodies keep in mind that anything that can happen naturally will some day become selectable using biotechnology. If the people who have extra muscles gain some performance advantage then expect some parents in the future to opt for genetic engineering to give their kids the extra muscles on purpose.
Adding extra muscles to adults will become possible when advances in stem cell research and tissue engineering provide the ability to grow replacement muscles either inside or outside the body. But making those muscles useful might be much harder because wiring up neurons to the muscles and then training the brain to control them appropriately could turn out to be quite difficult.
By Randall Parker at 2006 September 02 10:14 PM Trends, Human Evolution | TrackBack"(triceps? quadraceps?)"
triceps would be a problem, as that term is generally used to refer to the triceps brachii (which extend the arm), whereas biceps is generally used for the biceps brachii (the contract the arm). It wouldn't be entirely incorrect to refer to other two-muscle-combinations as biceps (such as the biceps femoris, on the thigh), but it isn't really general usage. My guess is that the new muscle won't lead to a change in the name "biceps brachii", and certainly not to "triceps brachii" (since that's taken), and thus the shortened name is likely not to change either. However, it would be kind of neat to be able to say "my biceps are triceps". :)
Where was this published? Can you please post the citation? Thanks!
This is all new to me but I thought I would share this. A few weeks back I had an elbow surgery and when the surgeon was done he explained that some of the problem with the ulnar nerve compression was that I had an extra muscle compressing the nerve in my triceps. I had not given it much thought until seeing this on the internet. In some it might be good to have extra muscles but seemingly in my case it was part of the problem. Guess that is what makes us all human and different.
Like Jason's comment, I just had surgery to decompress the ulnar nerve two weeks ago. My surgeon said I have an extra muscle that was putting pressure on the nerve causing numbness in the fingers and pain in the elbow. Wow, I knew I was strong, diddn't know it was due to extra muscles! What a great improvement this surgery has done for me!
This is funny, but same here. Had the surgery two weeks ago and doctor stated that I have an extra muscle putting pressure on the ulnar nerve. Maybe it is a next step. :)
I am a sprinter and I have an extra muscles in my calfs. My mum always says it will make me faster but I have had to give up running because of the problems I was having. I caused my feet to break my feet 3 times. I am considering surgery but need some advice. Just thought I would post a comment incase anyone had any suggestions.