There are five professions(1) but lots of occupations and trades lay claim to being the oldest one despite predating the concept by millennia.

Farming is around 14,000 years old but a new study reveals one less-considered trade predates it by tens of thousands of years: fashion.

Humans wore clothing prior to that, but fashion is a different animal skin. It is clothing for social and cultural purposes, marking the major shift from clothes as protection to clothes as an expression of identity. Paleolithic eyed needles are now known to be as old as 40,000 years, and with it came the evolution of dressing. 

Eyed needles are more difficult to make when compared to bone awls, which people used to make functional clothing. A hide scraper and an awl was enough. No one needed anything more advanced, eyed needles didn't speed up the process of clothing, they instead slowed it done, because bone awls also need a perforated hole (eye) to facilitate the sewing of sinew or thread. There was no reason to add an eye when bone awls were already creating tailored clothes.


Artistic rendition of fashion over function during the Upper Paleolithic. By Mariana Ariza.

That means they were created in order to make more complex, layered clothing, as well as attaching beads and other small decorative items onto clothes.

The oldest needle to-date was found in Siberia, where it makes sense to adorn clothing. It is cold now and was really cold then so warm-weather decorations like body painting with ochre or deliberate scars were never going to be seen the way beads and other accessories could be. You had to wear it anyway, why not make it fabulous?

In solitude, we don't need clothes at all but as tribes formed, ways to be individual likely became popular. As did ways to show you were part of a tribe when traveling. That psychology is still with us today. If you think someone looks cool, you may dress like them. 

That may make you feel more confident. Which is always a good thing.

NOTE:

(1) Medicine, military, engineering, education, law. Everything else is an occupation or trade but that doesn't stop car sales people from using the term anyway.