Linguists: Why does a language's grammar simplify over time?

But we do have “both” meaning “all two”, as German as beide. AFAIK there is no such word in the Romance languages, both being translatable into French as tous les deux.

Maybe it isn’t so much of a hijack. With the loss of postfix inflection of English has come an increasing use of auxiliary verbs, which happen to be irregular–to be, to do, and so forth. So it isn’t quite true that all the meaning that used to be carried by the postfixes is now being handled by syntax; rather, some of the inflection has merely moved to the auxiliary. Perhaps after a few millenia, we will have in English words like “isgoing” and “aregoing”, which would be examples of prefix inflection.

Not really – the modern Celtic languages inflect words by changing the initial consonant, adding suffixes, and (in the case of Gaelic) palatalizing the final consonant. A few words are also inflected by changing the vowel (e.g. in Manx, the genitive of “cass” “foot” is “coshey”).

For a good example of a language that has inflections at the beginning rather than the end of words, look at the Bantu languages. As an example, the plural of the Swahili word “kitabu” “book” is “vitabu”.

I’m glad English doesn’t do anything complicated like that.

“Listening to the wise advice of their mothers-in-law, the herdsmen moved the oxen and sheep to safety at the lee of the chateaux.”

Wouldn’t Spanish ambos have the same use?

**Q: ¿Vas a comprar el Dalí, o el Picasso?
A: Ambos, si puedo.[/B]
[Q: Are you going to buy the Dali or the Picasso?
A: Both, If I can.]

Does it decline as a dual word?

I’ll just chime in a bit late stating that John Hawkins has a book that basically spends 300 pages arguing that humans are lazy (I suppose similarly to the Deutscher book mentioned before). When we can convey the same information (without misinterpretation) with less words/morphemes, then we will do so. It’s all comes down to efficiency, which he explains with some odd mathematics.

So, at least in the case of English, with had developed a fairly strict word order, inflections became inefficient, and hence gradually disappeared.