Yet another one :P I decied to bust yet another myth people think is true but really isnt
It is about how languages developes, the myth goes that languages over time always simplify getting rid of unneccisery stuff. This could not possibly be further from the truth, languages CAN simplify over time but this is not its natural tendency at all. The natural tendency for languages is to accumilate more dirt, more features, more everything to get ever more complicated reaching complexity levels people in the west cant think is possible. Why is this the case and not the original idea? why does it exist and why have languages acctually been simplified? I will first explain why it gets more complicated with time and explain why it also simplifies in instances.
The instance of complicating comes from generations shifts, perception of things and more. A language lets say starts with a specific word, a preposition for the sake of argument here, after nouns, the first people will naturally percieve them as two individual words but you will at some point get perhaps a generation that starts percieving it as one single unit, one entity of language and pronounce it in accordance. Notice should be made this is before writting, the original generation that dont have this perception (if at all left) will only think of it a slight pronouncation differens which is quite common for everyone who have siblings, family or know dialects. But once that generation is gone all forth comming generations will percieve it as one single unit of meaning, with some phonological changes you soon enough get a case that bare little to no resamblance with the original word.
And example can be english -ed which is thought to come from "did" like verb, if one say "i walk did" fast and often enough it gets pronounced as "i walked" so what was once an individual word started getting stuck and eventually eroded into something else, an important thing is to think on is that sound changes cant act between words normally (naturally exceptions do occure) but does in the individual unit of meaning. with more gluing on over time and sound changes you can get increadibly big inflection tables because they will all differ, if we use spanish and english togather for fun and start with hablo and hablas (i speak, you speak) and have "did" again, "hablo did" "hablas did" you can end up with hablid (or perhaps habloid) for "i spoke" and and hablasid for "you spoke" and so on. The table can grow over time and start perfectly regular but sound changes will start messing it up.
But sound changes alone will not cause all changes, another one that can cause huge shifts in a language to complicate it more is humans will to regulize everything. Alot of things happen because we want order, if a sound change occures and we see it or simular to it being more often used we will start percieving it as such a marker. For example in old english plural form of foot, feet, was "foti", but also singular dative form was "foti", in anticipation to the "i" sound people pronounced it as "feti" instead, but because plural accusative form is more used than singular dative people thoguht the "e" in "feti" was a plural marker hence singular dative was returned to "foti" while accusative plural became "feti" which with more changes ended up with "foot" and "feet" we have today. An attempt to create order resulted in an irregularity in English.
Features can also be acquired by it originally being used for emphazis but eventually becomes everyday usage, for example english "be x-ing" is such, probably originally used to mark the person is doing it right now but eventually became the standard expression of current doings. French have the "ne X pas", the ne is no longer pronounced but was originally the negator, then "pas" came from trying to make emphazis on such as "he doesnt walk a step", but again a generation came and percieved the emphazis marking as standard and it lost that and became part of regular expression.
All of those changes and more makes it so with time a language acquire more function, inflections and so on and eventually end up as perhaps polysynthetic language, or not (as we got the entire range). Human psychology plays a vital role in this as language is after all how we percieve meanings and things.
But for simplification, how does it arise? There is two reasons it can occure which are both related. The first is simply that a large amount of non-native speakers in a region learns the language not as kids but closer to adulthood and hence learns it incomplete which is passed onto the next generation, inflections and such are usually first to go in such cases. This can on the other hand also introduce new features such as english Do-support for questions and negation which comes from celtic people trying to learn english and started using it like they were used to. But once a region have this "degenerated", which it isnt as the point people want to make sitll get across and as long as that works a language is as good as any, it can start spreading outward which is exacly what happened, a region was inhabitated by many vikings that learned english incompletely which in turn spread out slowly and where vikings never reached preserved things as far as into late 19th centry in some ways.
This is also the major culprit for Indo-european (IE) languages seemingly having gotten simpler over time, we spread more and learn from each other and it have permanent effect on a language, not all are affected but most and many have. But this have also marked europe for example with what one can call "european linguistical features" which is almost soley in europe but no where else, how do we know its not an IE feature? simple, languages unrelated, basque, finnish etc, have same features meaning it is something we all have shared among one another. an example is definitiveness which exists in middle to west europe but eastern and slavic languages lacks it.
The second way it goes simpler is by a bunch of people collecting in an area all speaking different languages and some of them perhaps gets more status and their language more prone and with that they try learning it and again being incomplete and the rest is basicly the same. this occures more often in new areas of collection than old ones.
Language develop is complicated, many factors and changes can occure at once, what starts in one corner can slowly spread through out the language while in another corner another change occures and spreads both eventualyl reaching everywhere but at some areas they overlap earlier than others and so on. The final conclution is that a language never get simpler by nature but its more or less always outside forces that causes it while internal forces will build it up over time.