Last week we discussed the relationship of German to English and the many other languages of northern Europe. As mentioned in class, the relationship goes back thousands of years, to a shared common tongue across much of modern-day Europe. The first link, to a page of Professor Clark Ford at Iowa State University, includes the illustration of the language tree which we saw in class. The second is a link to the Wikipedia article on Indo-European languages. There's quite a bit of information there, but take a look at the information on Germanic and Proto-Germanic.
Language Tree
Indo-European Languages