Also, vitamins deficiency might set in at different times for adults and children. Children grow a lot, so their nutritional needs are probably different from adults.
No source, just speculation.
There are cases of people with no sense of pain. Here's an article about it:
...and a link to the primary it references, if you have a subscription to Nature:
A relevant quote from the review:
"The team's first research subject, a 10-year-old boy, was well known in his community for street performances in which he placed knives through his arms and walked on hot coals. Despite tissue damage, he apparently felt no discomfort."
Other mutants for the same gene were similar -- they generally enjoyed showing off their lack of pain by deliberately injuring themselves. One killed himself by jumping off a roof, I believe just after the above article was published (sorry, I'm not really sure where I read that). Living without pain is generally an unhealthy idea. Without visceral negative feedback, humans don't place value on bodily integrity and tend to self-terminate, which is probably why those mutants are incredibly rare.
Perhaps once aversion reactions have been formed, knocking out pain receptors would be a good thing. I'd certainly be curious to see if people still avoid injuring themselves if they lose the ability to feel pain AFTER they've experienced it all their lives.
Hello from the lurking shadows!
I've pretty much always been at least an aspiring rationalist, and I convinced myself of atheism at a pretty early age. My journey to LW started with my discovery of Aubrey de Gray in middle school and my discovery of the transhumanism movement in high school. Some internet prodding brought me to SL4, but I was intimidated with the overwhelming number of prior posts and didn't really read much of it. The little I did read, however, led me to Eliezer's Creating Friendly AI, which struck me on perusal as the most intelligently-written thing I'd read since The Selfish Gene. Earlier this year, the combination of reading through a few of Gardner Dozois' short "best of" short story collections and the discovery of Google Reader brought me to some of Eliezer's posts on AI and metaethics, and I've been reading through LW ever since. I'm currently plowing slowly through Eliezer's quantum physics sequence while trying not to fall behind too much on new threads.
My primary short-term goal is to learn as much as I can while I'm still young and plastic. My primary mid-range goals are to try to use technology to enhance my biology and to help medical immortality become practical and available while I'm still alive. My long-term goals include understanding physics, preserving what's left of the environment, and maximizing my happiness (while remaining within reasonable bounds of ethics).
I also have a passing but occasionally productive interest in writing science fiction, as well as a strong interest in reading it.
Hello, I'm an undergrad student who's been reading LW for about six months now. So far I've stuck to lurking for a couple of reasons. For one thing, most of the comments I have are already made by other people. Also, there's enough information on LW that it seems more fruitful to move on to a new article than to post a question.
There's a LOT of background reading available here on LW, which is intimidating to a new reader. I can say for myself that it's difficult to bring myself to post when I know there are dozens of background articles I still need to read. That's probably a good thing, though -- from what I've read about SL4 (and what I read in my brief forays there), LW has avoided a lot of the redundancy and conversational looping that its predecessor had.