It's astonishing that we can surround ourselves with so much of a substance that most of us know nothing about. What exactly is plastic? Is it normal? Is it an alien stuff that has been sent to us? What material is it composed of? Plastic is a substance made up of any synthetic or semi-synthetic polymer. A polymer is defined as "a big molecule composed of chains or rings of connected repeating components known as monomers." Natural polymers include silk, rubber, cellulose, keratin, collagen, and DNA, and it is the form of the polymer that gives plastic its 'plasticity.'
Plant cellulose, a natural polymer, was used to create the first synthetic plastic, which can be seen under the microscope here. Plastic's 'plasticity' is due to the characteristic polymer form observed in this picture of long chains of subunits bonded together. A naturally occurring molecular structure. So, while the majority of the plastic we use today was created in a lab using oil-based chemicals and science, the structures that give plastic its adaptability are borrowed from nature.
The very first human-made plastics were actually praised as a solution to various environmental issues, with pamphlets saying things like "As petroleum came to the relief of the whale (people used to use whale oil), so celluloid (first human-made plastic) has given the elephant, tortoise, and coral insect a respite; and it will no longer be necessary to ransack the earth in pursuit of substances that are constantly becoming scarcer."
Yes, the main motivation for the creation of synthetic plastics was elephant ivory.