World's primary sources of energy: A historical timeline 

Early civilisation: Sun

In the early years of civilisation, humans relied upon the sun as an energy source. It provided heat and light. Wood was burned for heat and water was used to generate basic mills. 

Pre industrial revolution: Wood, crop waste and charcoal

Until the industrial revolution, energy sources remained similar. The traditional biomass - burning of solid fuels such as wood, crop waste or charcoal were the primary sources of energy. Manual labour and animals were also utilised. Windmills and watermills were in use but in very minimal capacity.

Industrial revolution: Coal

From the 1750s, coal began to come into use to power tools and machinery. Coal became a dominant force; it was used to power steam engines. After a certain point, coal saw an increased use in power plants. Power generated from coal was the core driving force behind the Industrial Revolution.

20th century: Oil and natural gas

Near the beginning of the century the world was heavily reliant on coal but as other sources began to be explored, coal began to lose its footing gradually. Oil powered ships took to the stage and coal took a backseat during that time. Along with oil, natural gas was the primary source of energy. Nuclear fission, a new energy source was discovered and came into use. Renewable forms like hydroelectric, wind and solar were explored but were not used widely. 

21st century: Renewables

The trend of mass fossil fuel use had, as predicted by climate scientists, begun to alter the climate for the worse. To combat climate change and reduce greenhouse gas emissions, the world began to look for renewable energy. Though still a work in progress, trends suggest that non renewables will be the way to go for the rest of the century. However, efficient clean energy has been the motto the world has strived for. Biotechnologies have made several advances and this only proves the potential of biomass-derived fuels. Other than that, wind and solar energies have been a significant share of energy sources.