Why did English evolve to have so little inflection? [duplicate]

Question

Consider the sentence,

The boy hit the ball out of the yard.

If we think of the words which make up the sentence, we realize that none of them have much inflectional possibility. The conjugation of hit is so uniform that one wonders why the third person singular even varies from the rest. (I hit, you hit, he hits, we hit, you all hit, they hit.) The nouns only inflect to show whether they are singular or plural. (Boy, boys, ball, balls, yard, yards).

It would seem that word order takes over all these functions. Word order shows us that boy is the subject, the one doing the hitting, not ball or yard. It also shows us that ball is the object, as opposed to yard, and that yard is part of a prepositional phrase.

How did the English language come to rely on word order instead of inflection? Are there any advantages to this system that enabled it to spread? Is it safe to say that Indo-European languages start out being more inflected, and then become less inflected over time?

I suppose I am asking two questions, really.

1. Why is English this way?
2. Is there a trend of Indo-European languages becoming less inflected over time? If so, why?

Answer 1

There is a trend for languages, in general, to lose inflection of a certain type, and Indo-European languages manifest that trend. Particular facts of English have encouraged that development, and different facts of Indic or Greek encouraged similar developments. The main fact about Indo-European morphology (or, late versions if its morphology) that presages the doom of the inflectional system is its arbitrariness. Nominal gender, number and case affixes were not transparent, one form for one meaning; likewise verbal inflection. As more arbitrary differences accumulate and patterns become manifested over fewer and fewer forms whose unifying nature is harder to discern, it becomes more likely that former distinctions will no longer be maintained. Various phonological facts, especially vowel reductions, contribute to the specifics of why Modern English is so reduced, compared to Old English.

Answer 2

Typically there is only so much in the way grammar systems tend to simplify on their own and this usually does not lead into complete loss of entire categories on such a grand scale (typically there are only some regularisations by analogies etc.).

The reason why English lost most of its inflection actually has very little to do with grammar at all - it is caused by sound change. English heavily reduced all non-accented syllables, which, given the IE inflection being based on suffixes and endings, resulted in mergers and loss of most of these endings. Note that when the inflection is stressed, it is typically also preserved, i.e. the shortest words like the various forms of verb to be or the pronouns.

The same process happened in French - all post-accentual vowels were eventually reduced and original word-end consonants followed the same fate. Again, given the way IE endings look like, this was not a particularly healthy environment and thus French lost all its declension and eventually large part of conjugations (until it developed its own based on alteration of stem vowels and consonants).

Given the specific requirements to create new inflection, there is indeed a sort of a "trend" to lose inflection (given how unbelievably complex the PIE language was), however new inflections still arise, e.g. the Romance languages evolved a new synthetic future tense, Polish turned the Slavic analytical past tense into synthetic one, French can be considered developing prefix-based conjugation (but most traditional looks into analysing the language are not yet ready to accept it).