In the last episode of the Ray Mears series “How the Wild West was Won” on BBC 4, he featured the homes of the Navajo Indians in the Sanoran Desert in the south-west of the USA. Their houses were called hogoms, and they consisted of earth piled up on a pyramid-like timber frame to provide one large simple volume. Because of the heat, the earth became baked hard and dry. However, there was also occasional torrential rain and if any earth was washed off, it could be repaired using the material which was all around – more earth. The timber itself was a scarce resource, and so it was re-used if homes had to be re-built. Again the structures were warm in the winter but cool in the summer.