The word renaissance come from French and literally translates to (re) again (naissance) birth. So essentially the Renaissance was a rebirth of sorts, but a rebirth of what? To find out we need to back to antiquity and not as in when antique furniture is from, but 3100 BCE, with the unification of Ancient Egypt.
(3100-332 BCE)
Art in Ancient Egypt was not design to be naturalistic, but rather, to depict power. Stoic, rigid and always facing forwards with one foot advancing in confidence.
(1100-500 BCE)
Occurring at the same time as Ancient Egypt, the style is very similar in its pose. The Greek sculptures (or kuros), however are slightly more naturalistic and dynamic
(500-323 BCE)
Developments in sculpting let to much more naturalistic depictions of the human form. A bending on the knee lead to a gentle curving of the spine in the contrapposto pose.
(323 BCE- c.300)
Once confident in the sculpting of realistic figures, artist began to experiment in dynamic portrayals of the figure in motion.
(5th-15th Centuries)
After the fall of Rome, realistic figures of gods and athletes gave way to religious images in flattened space as realistic sculptures would be considered idols.
(15th Century)
The Renaissance was a re-birth of classical ideals of balance and harmony. This, paired with new discoveries in perspective led to a golden age of art.