The earliest clothes were crude attempts to cover the human body to protect it from vagaries of nature. As mankind found newer metals and as we moved from Stone to Iron Age, the protective options against nature also increased. Humans were now in a position to cut down trees and they made use of bark and leaves to cover themselves well.
The earliest clothes were probably created by tying different parts of animal skin or leaves and bark together. The process of innovation and creativity began from that day onwards. Till date, mankind is still finding newer and better ways to make clothes.
As civilization improved and as mankind grew stronger in its battle against nature, leisure time increased and scope for innovation also increased. Needles and thread were invented and better clothes were stitched. The exact age when different people started wearing different clothes and human beings started wearing more than one piece of cloth on the body is not known.
However, clothes became common once the needle and thread was invented. However, many centuries were to pass before further improvisations were made. There was no device available that could automate the process until the sewing machine was invented.
Stitching by hand was finally replaced by machine stitching only after the industrial revolution took place in Europe. Sewing machines were invented along with various other devices and stitching finally became a mechanical job instead of a laborious one.
Today, stitching is primarily done by machines because it is very easy to stitch large number of clothes without loss of quality. Earlier, clothes were held together by very loose threads. Today, even tough denim fabric can be held together by strong stitches and even rivets can be fitted into the clothes to improve strength. All this has taken place simply because of advancement of technology.