Some bogs have preserved bog - wood such as ancient oak logs useful in dendrochronology , and they have yielded extremely well preserved bog bodies , with organs , skin , and hair intact , buried there thousands of years ago after apparent Germanic and Celtic human sacrifice .
Some bogs have preserved bog - wood such as ancient oak logs useful in dendrochronology . 
 Bogs in Denmark , Ireland and England have yielded extremely well - preserved bog bodies , with organs , skin , and hair intact , buried there thousands of years ago after apparent Germanic and Celtic human sacrifice .