because they worked really hard on whatever they were doing.
The Phoenicians improved upon the Sumerian invention by when the Sumerians invented the first writing system (symbols and cuneiform) the Phoenicians invented the alphabet which was easier.
The Greek invention that aided navel travel and that was improved upon by the Muslims was Greek fire.
It has already been improved. Pencils have many colors and hardness values. Pens are a type of pencil with ink instead of graphite.
There was no single "original invention".
the sumerians strove to please their gods because they belived their god could bring them good or bad things upon them
Johannes Gutenberg Gensfleisch
Several chance encounters influenced Thomas Edison's spirit of invention. In 1862, he rescued a child from the train tracks As a reward, the child's father taught him telegraphy. Telegraphy skills set him on the path to some his greatest inventions afforded him the opportunity to travel, perfect his scientific experiments and start the Invention Factory. Alexander Graham Bell's invention of the telephone inspired him to experiment and improve upon the model. His meeting with Edward Muybridge led to the invention of the motion picture.
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IM PRETTY SURE IT WAS THOMAS ALVA EDDISON WHO HELPED ALEXANDER GRAHAM BELL IMPROVE HIS TELEPHONE INVENTION. LISTEN I AM ALONE AND AT CROSSROADS
to improve upon the older telephones
They didn't, but they replaced them with the constitution.
No. It would be almost impossible to improve upon the original.