More on the 'cladistics' of sequences

[SKÁLA Zdenek]

Thanks Pierre; my point was probably even simpler than your (kind) interpretation:

pierre:
.. the outgroup criterion is 
classically based on a decision as for some resolution of the phylogeny at 
a larger scale, and not on a phenetic criterion.
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True, but for this 'larger scale' the same problem arises - the larger-scale cladogram have been constructed by some outgroup and the outgroup has been chosen in some way and then... Finally we can go up to the tree-of-life-outgroup problem (quoted by you) but in practice (as far as I know) it is usually not the case - for practical reasons ("too-far-outgroup problem" can be similarly hard as "ingroup problem" - at least for morphologic data).

Best!
Zdenek