As different nations colonise and wage war on one another they inherently begin to adopt the language and accents as the generations of settlers and conquerors go by. They begin to pile on top of each other and eventually there comes a point where there are no more settlers or conquerors coming in the masses so the language and the accent begins to stabilise. The English language has been learning to adapt and evolve throughout its existence from 360AD onwards. However the language became almost entirely french during the Norman Invasion during the 11th Century. With the courts of England speaking in French and not Anglo, but seeing as the Normans never completely pressed the lengths and breadths of the country it only affected the ruling classes of the south and started to trickle up the country, the languages mixed and became a Frenchified Anglish or as we would know it, English. This has been noted by J.R.R Tolkien as a tragedy for English Mythology and Literature.
As a Scots Brit I am constantly reminded of just how languages change and evolve. A lot of people, including Scots themselves see the Scottish tongue as an accent unless you speak Gaelic. This is mostly not true for those living in the lowlands. Many Scots, without knowing, speak what is now realised by the European Charter for Regional Languages as Modern, Braid or Lallan (Broad or Lowland) Scots. To show how it's written you can take a look at the wikipedia extract from the New Testament in Scots.
This is the storie o the birth o Jesus Christ. His mither Mary wis trystit til Joseph, but afore they war mairriet she wis fund tae be wi bairn bi the Halie Spírit. Her husband Joseph, honest man, hed nae mind tae affront her afore the warld an wis for brakkin aff their tryst hidlinweys; an sae he wis een ettlin tae dae, whan an angel o the Lord kythed til him in a draim an said til him, “Joseph, son o Dauvit, be nane feared tae tak Mary your trystit wife intil your hame; the bairn she is cairrein is o the Halie Spírit. She will beir a son, an the name ye ar tae gíe him is Jesus, for he will sauf his fowk frae their sins.”
This is rather difficult to read for a lot of Scots because we write and read in English and almost completely incomprehensible for anyone outside of Northern Britain. However if you were to have someone speak it to you and you were a Scot it'd be easily understood, you may even be able to understand it if you weren't Scottish.
I find the way that languages work and the way we reclaim our languages from accents and how we evolve our accents from languages to be entirely fascinating.