So now there's a secret conspiracy about twins? The only person I can think of that was obsessed with twins died in 1945. 

The longstanding question is how much is determined by genetic pre-programming versus environmental factors.
 
Identical twins are genetically identical because they come from the same egg, it's been assumed that any post-birth differences between twins must be non-genetic in origin. If one gets arthritis and the other does not, it means that something in the arthritis sufferer's environment triggered the disease.
 
Recent research, however, shows that our DNA changes over time. So it's not simply a case of nature vs. nurture, but rather an interplay between them. Genetics win out in some cases but not others. Alzheimer's, for example, is largely predetermined by your genes (bad news for me) and there isn't much you can do about it (yet). But Multiple Sclerosis does not appear to be genetically predetermined, suggesting that there might be as-yet unidentified environmental factors. 
 
The height change, btw, is the result of spinal decompression due to weightlessness, and is temporary.

bitflipper
The longstanding question is how much is determined by genetic pre-programming versus environmental factors.
 
Identical twins are genetically identical because they come from the same egg, it's been assumed that any post-birth differences between twins must be non-genetic in origin. If one gets arthritis and the other does not, it means that something in the arthritis sufferer's environment triggered the disease.
 
Recent research, however, shows that our DNA changes over time. So it's not simply a case of nature vs. nurture, but rather an interplay between them. Genetics win out in some cases but not others. Alzheimer's, for example, is largely predetermined by your genes (bad news for me) and there isn't much you can do about it (yet). But Multiple Sclerosis does not appear to be genetically predetermined, suggesting that there might be as-yet unidentified environmental factors. 
 
The height change, btw, is the result of spinal decompression due to weightlessness, and is temporary.

Nice ... thanks. The decompression makes sense ... way better sense than previously.

bitflipper If one gets arthritis and the other does not, it means that something in the arthritis sufferer's environment triggered the disease.

It could just as equally mean that something in the NON sufferer's environment prevented him from getting the disease that he should otherwise have got due to genetics.
 
It doesn't actually prove anything one way or another...

Karyn

bitflipper If one gets arthritis and the other does not, it means that something in the arthritis sufferer's environment triggered the disease.

It could just as equally mean that something in the NON sufferer's environment prevented him from getting the disease that he should otherwise have got due to genetics.
 
It doesn't actually prove anything one way or another...

I agree to this ... well stated. it kinda goes both ways ... as changes are changes but there is no way to mark and define the starting and ending points for any of these events, and what they caused. One might be able to define these in a psychic manner, but reversing it is not usually a do-able exercise, which might also suggest that the "source" is not quite right. It has been done, and many writers have discussed this, specially the Castaneda group women, all of them being considerably better writers than Carlos.

This topic reminds me of the time I had to work with this blond for 365 days...