Presented without comment:
Recent genetic analyses have revealed that, over centuries and millennia, it is generally languages and not peoples that are replaced. That is, new languages are readily absorbed by relatively stable populations. In this way, for example, the pre-Celts of the British Isles and Ireland adopted the Celts’ minority languages when these Indo-Europeans intruded. Their descendants, many centuries later, similarly adopted the minority language of the invading West Germans (‘Anglo-Saxons’), while the islanders’ genetic profile remained relatively unchanged. This is a phenomenon that has occurred innumerable times around the globe. Throughout history, human societies have donned new languages like new cloaks. The linguistic metamorphosis always went unnoticed – until there was writing.
From A History of Language by Steven Roger Fischer, Director of the Institute of Polynesian Languages and Literatures in Auckland, New Zealand. Later in the book, Mr Fischer has written a line I offer as a mantra to linguistic purists:
All linguistic contact is enrichment.