As evidence, they highlighted the existence of a posthole near to the monument's southern entrance that would have once supported a large wooden post. Although this posthole was never dated when it was excavated in the early 20th century, and so cannot definitely be ascribed to the Mesolithic, Gillings and Pollard noted that its positioning had no relation to the rest of the henge, and that it may therefore have been erected centuries or even millennia before the henge was actually built. They compared this with similar wooden posts that had been erected in southern Britain during the Mesolithic at Stonehenge and Hambledon Hill, both of which were sites that like Avebury saw the construction of large monuments in the Neolithic. In the 4th millennium BCE, around the start of the Neolithic period in Britain, British society underwent radical changes. These coincided with the introduction to the island of domesticated species of animals and plants, as well as a changing material culture that included pottery. These developments allowed hunter-gatherers to settle down and produce their own food. As agriculture spread, people cleared land. At the same time, they also erected the first monuments to be seen in the local landscape, an activity interpreted as evidence of a change in the way people viewed their place in the world. Based on anthropological studies of recent and contemporary societies, Gillings and Pollard suggest that forests, clearings, and stones were important in Neolithic culture, not only as resources but as symbols; the site of Avebury occupied a convergence of these three elements. Neolithic activity at Avebury is evidenced by flint, animal bones, and pottery such as Peterborough ware dating from the early 4th and 3rd millennia BCE. Five distinct areas of Neolithic activity have been identified within of Avebury; they include a scatter of flints along the line of the West Kennet Avenue – an avenue that connects Avebury with the Neolithic site of The Sanctuary. Pollard suggests that areas of activity in the Neolithic became important markers in the landscape. During the Late Neolithic, British society underwent another series of major changes. Between 3500 and 3300 BCE, these prehistoric Britons ceased their continual expansion and cultivation of wilderness and instead focused on settling and farming the most agriculturally productive areas of the island: Orkney, eastern Scotland, Anglesey, the upper Thames, Wessex, Essex, Yorkshire and the river valleys of the Wash.  Late Neolithic Britons also appeared to have changed their religious beliefs, ceasing to construct the large chambered tombs that are widely thought by archaeologists to have been connected with ancestor veneration.