The Earth has a very, very long history, of which humans occupy only a tiny and most recent part. Understanding the past helps us understand the present world — as E.H. Carr wrote, we can fully understand the present only in the light of the past. The National Museum in New Delhi preserves objects from the past — statues, coins, ornaments — all of which help us understand our history.

Every object or structure tells a story and is like a piece in a jigsaw puzzle. Historical events can be reconstructed through a variety of sources. However, quite a few pieces of the puzzle may remain missing — history is always incomplete and must be pieced together carefully.

Fig. 4.1 — Timeline of a few important stages in the evolution of life on Earth. Three scales are used: billion years ago (light blue), million years ago (dark blue), and years ago (green). (Source: NCERT)

The timeline shows the vast scale of Earth's history relative to human existence. Key milestones:

In addition, in the last 50 years or so, scientific studies have increasingly contributed to reconstructing the past: studies of ancient climates, chemical studies of excavated materials, and genetics of ancient people have provided fresh insights supplementing traditional sources. For recent history (last 2–3 centuries), newspapers and electronic media (television, internet) also serve as historical sources.

Each society and culture has had its own ways of measuring time. Major events — such as the birth of an important person or the start of a ruler's reign — have often marked the beginning of a new era.

At present, the Gregorian calendar is commonly used worldwide. Side by side, Hindu, Muslim, Jewish, Chinese, and other calendars are also used — especially for calculating dates of festivals and other auspicious events.

Timeline showing the birth of Buddha (560 BCE) and Jesus' birth, relative to 2000 CE (present) and the Future. Note that BCE years go left (toward Past) and CE years go right (toward Future). (Source: NCERT)

A timeline also helps understand the order of historical events. For example: Even without knowing the exact dates, a timeline shows that the birth of the Buddha occurs before the birth of Jesus.

Fig. 4.3 — Timeline of some main events since 300,000 BCE. The dotted portion represents a skipped period (otherwise the timeline would be 3 metres long!). First examples of rock art in the world: ~40,000 BCE. Ice Age marked around 14,000 BCE. (Source: NCERT)

Detailed timeline from 12,000 BCE to 2000 CE showing key events: End of last ice age (12,000 BCE), First settlements and beginning of agriculture (8,000 BCE), Pottery in Indian Subcontinent / World's first cities in Mesopotamia (6,000 BCE), Beginning of copper metallurgy / Indus-Sarasvati civilisation (4,000 BCE), Birth of Jesus (2,000 BCE), Birth of the Buddha / Ashoka (~560 BCE / ~250 BCE), "We are here" (2,000 CE). (Source: NCERT)

A timeline is a convenient tool to mark events, as it shows a sequence of dates and events covering any particular period. The dotted portion in the NCERT timeline marks a skipped period; otherwise, the timeline would have to be almost 3 metres long!

Mind map of Sources of History from NCERT (page 67). Central circle: "Sources of History". Four main branches: Archaeological Sources (with Inscriptions, Structures, Excavations, Artistic Sources), Literary Sources (Indian Literature, Foreign Accounts), and Oral Sources. (Source: NCERT)

When historians study any period, they gather information from as many sources as possible. Sometimes sources confirm each other (jigsaw pieces match); at other times they give contradictory information (pieces don't match) — in which case historians must decide which source to trust more.

Archaeological sources are the most important for ancient history (before writing was invented). They are obtained through excavations, surface surveys, and study of monuments.

Historians themselves contribute to sources of history, but also: archaeologists, epigraphists (who study ancient inscriptions), anthropologists, experts in literature and languages, and many more specialists. All of these together help piece together our understanding of the past.

In the last 50 years, scientific contributions have grown enormously:

• Studies of ancient climates — tell us about environmental conditions that shaped human choices
• Chemical studies of excavated materials — determine age, origin, trade routes
• Genetics of ancient people — trace migration patterns and population histories
• Radiocarbon dating — scientific method to determine age of organic materials

Modern humans (Homo sapiens) have walked the planet for about 300,000 (three lakh) years. This is only a tiny fraction of the Earth's history, yet it encompasses an extraordinary journey of human development.

Life of early humans:

• Faced many challenges from nature; lived in bands or groups to help each other
• Constantly seeking shelter and food
• Were mainly hunters and gatherers — relied on hunting animals and collecting edible plants and fruits
• Had certain beliefs about natural elements and possibly some notion of afterlife
• Lived in temporary camps, rock shelters or caves
• Communicated using languages that are now lost
• Used fire (since ~1 million years ago)
• Made improved stone axes, blades, arrowheads and other tools
• Left rock paintings in hundreds of caves all over the world — some depict simple figures/symbols; others are more detailed scenes with animals or humans. First rock art: ~40,000 BCE
• Made simple ornaments: stone or shell beads, pendants made of animal teeth; sometimes exchanged with other groups — showing early trade/social networks

An illustration of an early agricultural community from a few millenniums ago, showing: harvesting crops, animal herding (sheep, dogs), use of tools (axe), cooking, thatched hut settlements near a river. This transition from hunting-gathering to farming changed human history. (Source: NCERT)

Over long ages, the Earth's climate went through many changes. At certain times, it was very cold and much of the Earth was covered with ice — called an "Ice Age." The last Ice Age lasted from over 100,000 (one lakh) years ago to around 12,000 years ago.

Afterwards, when the climate warmed up, ice partly melted, swelling rivers and draining into oceans. Living conditions improved, and in many parts of the world, humans started:

• Settling down near rivers
• Cultivating cereals and grains (first crops)
• Domesticating animals — cattle, goats, sheep, dogs, etc.

Why near rivers? Because of availability of water AND because soil near rivers is more fertile (due to sediment deposits), making crop-growing easier.

With more food available:

• Communities grew in size and number
• Social complexity increased
• Leaders or 'chieftains' became responsible for community well-being
• Initially, no individual ownership; lands were collectively sowed and harvested for community welfare

As time went by, the progression of human settlements followed this sequence:

Key developments in this progression:

New technologies appeared: pottery (for making pots and other clay objects) and the use of metal (copper first, iron later), which helped make durable tools, objects of daily use and ornaments. We will see in Chapter 6 how this stage prepared for the emergence of what is called 'civilisation'.

It is important to remember that this early progress of humanity had to face many challenges. At some critical times, humanity could have almost disappeared, as some earlier species (like Neanderthals and Homo erectus) did. We owe our existence to the courage and persistence of those early humans.