« on: 30/04/2015 19:17:37 »
Looks like petrified bark to me.
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The entire debate underlines the fact that "species" is not a defined term, any more than "race" is. We can assign living things to large arbitrary groups based on appearance but such assignments are of little predictive value. At the other end of the telescope we can in principle write down the entire genome for any individual, and this should be predictive, but in practice it is very difficult to do.
With what we know now, tobacco could not be declared "safe for human consumption" by smoking. I heard that a study of cancers in bodies from archaeological sites showed a similar incidence to today's population - except for an excess of lung cancer in modern populations, which was attributed to smoking. I haven't seen the same evidence for less-popular modes like chewing or snorting tobacco.