Who digs up the past

The chapter opens with the historian E.H. Carr: history is 'an unending dialogue between the present and the past ... between the society of today and the society of yesterday. ... We can fully understand the present only in the light of the past.' Put simply, history is the study of the human past.

Start close to home. What is the earliest memory you have? How old were you then? Those memories are part of your own past, perhaps going back five or six years.

Now widen it. The Earth has a very, very long history, and we humans fill only a tiny part of it, the most recent part. The book's timeline runs from the Earth's formation 4.54 billion years ago, through the first cells, sharks, insects and dinosaurs, and only reaches Homo sapiens (modern humans) about 300,000 years ago, and writing about 6,500 years ago.

Four kinds of experts help us read that past:

• Geologists study the physical features of the Earth: soil, stones, hills, mountains, rivers, seas and oceans.
• Palaeontologists study the remains of plants, animals and humans from millions of years ago, in the form of fossils. A fossil is a footprint, or part of a plant or animal, preserved in layers of soil or rock.
• Anthropologists study human societies and cultures, from the oldest times to today. An anthropologist might visit an old village and ask how people live, what they wear and eat, and which festivals they keep.
• Archaeologists study the past by digging up remains that people, plants and animals left behind: tools, pots, beads, figurines, toys, bones and teeth, burnt grains, parts of houses or bricks.