Well Clanad, whatever else I have an eye for, I certainly have an eye for the obvious. It seems to be making me a one-eyed man in the kingdom of the blind on here, but I am in good company, some of it even perhaps binocular, as you may be, but of course I wouldn�t know, would I?
Heath, if you think everything makes sense, you must have mentally supplied the missing word in 1: ... which [turned?] out to have changed fundamentally the course of English history...
Cool, what I think you are on about is ellipsis. For the relevant sense here, the COD is pathetic, to my surprise, but the Cambridge Advanced Learner's Dictionary has
noun [C or U] plural ellipses SPECIALIZED
when words are left out of a sentence but the sentence can still be understood:
An example of ellipsis is "What percentage was left?" "Twenty" (= 20 per cent).
But you are not on about it very consistently: your ex 2 is not even elliptical (if they survived at all.) What is more it couldn�t be elliptical here even if it wanted to be: try leaving out �they survived�!
But �if at all� in 1 is elliptical for �if they changed the course of English history at all�, or � if they did so at all�, and �if at all� in 3 is elliptical for �if related to his predecessor at all�, or �if he was related to his predecessor at all�, which alternatives show that there can be degrees of ellipsis!
How right you are that authors, and indeed speakers, omit some words in order to make their utterances neat and simple! If there was no ellipsis at all, they would be very tedious indeed, would they not? My last question tag, for example, would have to be �would they not be very tedious indeed?� Even if only a certain degree of ellipsis was possible, it would have to be �would they not be�!
See what Im getting at? And what all users of language are getting at?