The guitar is perhaps the most well known and most widely played instrument of all time. Naturally one might wonder where it came from and what influenced its making. Like most discoveries and inventions it came about almost by accident. .
For example the earliest guitars doubled as weapons such as small hunting bows, which doubled as a 'twanged' instrument which when held over the mouth of the hunter, turned their skulls into soundboards. The sound would resonate in their head and create the pitch. This kind of playing technique is apparently still used today. In present day it is known as the "okongao" or "cora" in certain parts of Africa. Other early guitars include chords strung over turtle shells, wires on clay pots, and strings over wooden bowls. ("Some guitar History") .
All these "early guitars" are very different from how the modern guitar looks. So when did the modern guitar first "take shape"? In the middle ages the female body inspired the art of the time. The trend was to relate art of all forms back to the female body. So it was during this time when they reshaped the guitar from the old strings on a round bowl to it having characteristics of the female body. For example the guitar became softly rounded at the shoulders, curving inward at the waist, and then ending with another gently rounded curve at the bottom. ("Some Guitar History").
Instruments similar to the guitar were invented in various countries at different times over the centuries. The ancestors of modern guitars developed in Europe alongside lute-like instruments, which are similar to guitars. Nobody seems to know for sure who the direct ancestors are. However, Crusaders returning from the east to Europe brought early versions of the lute and the vihuela. Europeans started experimenting on these guitars and eventually it evolved into the modern classical guitar. ("History of the Guitar").
Different kinds of plucked instruments came about and continued to influence the guitar.