Palaeolithic

The  was a time period on Earth. (PROSE: The Eight Doctors) The First Doctor and Susan visited the Palaeolithic along with Barbara Wright and Ian Chesterton during the latter two's first trip in The Doctor's TARDIS. (TV: An Unearthly Child) This trip was to circa 100,000 BC (PROSE: The Eight Doctors) during a period which the First Doctor thought of as the Stone Age. (PROSE: Doctor Who and an Unearthly Child)

According to Susan, Palaeolithic humans were sometimes found in glaciers. (PROSE: Time and Relative)

Behind the scenes
In the real world, the word "Palaeolithic" comes from Greek for "old stone age". It refers to a technological time period denoted by the use of primitive stone tools, lasting from approximately 3.3 million BP (before present) to 11650 BP. This at least partially coincides with the geological time period of the Pleistocene.