I don't see the left handed aspect as necessary for life. To me this just suggests our common ancestor for life on earth made use of this chirality. Another group of organisms somewhere else could have evolved from an ancestor that makes use of right handed chirality. Or one that is hand-blind.
replyI agree.
replyIt seems that the choice between left-handed and right-handed amino-acids was random.
However, it is unlikely that other kinds of life forms could use both kinds indiscriminately, because mixing them creates difficulties in the assembling of polymers. So it is likely that amino-acids produced by some extra-terrestrial life form would also be predominantly of only one orientation, but it could happen to be the right-handed variant.
Moreover, extra-terrestrial life forms could use very different complex amino-acids, because there are much more of those than the 11 that have been added to the simple amino-acids in the terrestrial proteins.