With the invention of agriculture, humans began to settle in permanent farming communities.
They also began to place some of their dead in large communal tombs - long barrows.
These were large earth mounds up to 70m long, with 2 long ditches on either side.
They had an entrance, a long corridor and a few rooms branching out on either side.
They would typically be built on hills.
It's difficult to spot them - but building structures such as these would have required a tremendous amount of work.
Men would first have had to deforest the land, using simple stone axes.
They would then have had to dig the earth, using deer antlers.
Finally, they would have had to carve out multi-ton rocks out of quarries and ferried them all the way to the house.
It's estimated that around 40,000 Neolithic long barrows have survived to this day.
West Kennet is one of the largest in the UK.
Over 1,000 years, around 50 people were buried here.
It was then mysteriously sealed up around 2000 BC and a decoy entrance created!
The other important long barrow site at Stonehenge, Normanton Down, is the largest group of barrows in the UK - with one Neolithic and 40 Bronze Age long and round barrows.
As experts at Maeshowe, a famous long barrow on the island of Orkney, describe it, long barrows were "an expression of genius within a group of people whose other tombs were claustrophobic chambers in smaller mounds".