Comparative Method linguists seem to use trade jargon words that are often diametrically opposed to how the rest of us would use those particular terms.
Consider this:
"POC *sa[??]apuluq, PNCV *sa[??]avulu 'ten" is replaced by PEE *rua-lima ('two-five'): e.g., Lewo lua-lima, South Efate ralim. (The same innovation, however, is found to the immediate north of this subgroup, in Paamese h??lualim.) "
The Efate-Erromango problem in Vanuatu subgrouping, John Lynch,
Oceanic Linguistics 43.2 (Dec 2004): p311(28) Available via JSTOR.
Anyone who has ever studied numbering systems, per se, would never describe 2x5 as a replacement for 1x10 (or 1 x group of ten). From 2x5 to 1x10 is, quite definitely, a conceptual step forward. So 2x5 shows the preservation of an older term, not an innovation.
The major problem is that comparative linguists go down the 'Snakes' to reconstruct a wholly imaginary proto-language, then climb up the 'Ladders', look back to their construction, and base their judgement of what exists in current languages on what they themselves invented.
This leads to a few more arse-about-tit linguistic jargon words:
Retention - means a word (or bit of grammar) that apparently descends directly from the imaginary proto-language
Innovation - means a word (or bit of grammar) that apparently doesn't descend from the imaginary proto-language
Reflex, reflected - means a word (or bit of grammar) that apparently corresponds to something in the imaginary proto-language
Conservative - means a language that apparently still preserves words (or bits of grammar) from the imaginary proto-language
In each case, the historical comparative linguist is referring back to (his own) imaginary proto-language, and not, in any way, to what might, just, have preceded that proto-language before it burst, fully-formed, into the world.
Henceforth in these posts, I will try to remember (as when I quote linguists directly) to highlight these linguistic jargon words, so you realise that they often mean exactly the opposite of what you (intuitively) might think they mean.
And I will try to remember to use completely different words myself:
Preservation - means a word (or bit of grammar) that still holds over from an earlier language.
Invention - means a word (or bit of grammar) that doesn't descend directly from an earlier language - it's genuinely new.
Descends from - means a word (or bit of grammar) that does descend directly from an earlier language.
Preservative - means a language that apparently still preserves words (or bits of grammar) from an earlier language