Humans are fortunate to see the world in greater detail and richer colours than most other animals, because of the types of cells we have in our retinas. The cost of this is that our night vision is poor. In the past most people withdrew to the safety of their homes when it got dark and they no longer had light to work by. This still occurs in the least developed parts of the world.
It is estimated that 1.6 billion of the world’s poorest people still have no access to electric lighting. At best they may use kerosene (paraffin) lamps to light their homes. The fumes from these cause respiratory illnesses and kerosene is quite expensive to buy.
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