The most obvious reason is that one has to pack up and go because things are not so good at home. Long ago, that probably meant that the climate had changed and made life impossible. It might have become too hot or too cold or too wet, which in turn would have affected not only quality of life but also make survival a shaky proposition. Drought, flood, and temperature changes could certainly push people to move on.
I hope that helped a little.
The election results were contested by the opposing party due to disputes over it.
Answer: The correct answer is : cones
Explanation: At the bottom of the eye there are millions of cells like cones and rods that collect the different elements of the spectrum of sunlight and change them into electrical impulses that then send them to the brain through the optic nerves. The cones are concentrated near the retina. The cones are responsible for the color vision.