Thousands of years ago, when tools were very primitive, it was probably common to have a favorite rock.

Wearing Jewels is the advanced form of carrying a pet rock.
- We're not so different than the penguins that prostitute themselves for rocks
  
  To be fair, the penguins don't care about the rocks they're just kinky like that

Paleontologists have found Neanderthal stone tools (knapped stone) made with high quality stone taken from kilometers away. This means that they had favorite tools that they wanted to keep with them, while other low quality stones where used few times before being discarded near their collection point
- "Yo dude checkout my secret rock spot, it's 13 kilometers over there"
  
  Even way back then, they already used the metric system!
- There's an area in the cascade range (western US, specifically oregon) that is a giant field of knapped obsidian, that was used as a training ground for young knappers, as well as a trading ground to trade knapped obsidian that has been found all over the western US. Not just miles, but many many miles. I'll see if I can go find a link.

Doing volunteer trail maintenance. All the people swarm the tool pile trying to claim their favorite pick mattock or grub hoe. It's adorable.
- You're my favorite grub hoe.
  
  😍

Umm.. I still have a favorite rock. His name is Doug 😂
- My favorite rock also has a name: Mount Saint Helens
  
  And what a great rock that is. Although temperamental at times.

I mean when I was young and used to play with rocks I had a favourite rock, I mean even painting rocks was a thing. No need to go thousands of years back lol

Sea otters exhibit this behavior. They keep their favorite rock in their pouches and use them to crack open shellfish.

My favorite rock has a first name, it's H-O-M-E-R. My favorite rock has a second name, it's H-O-M-E-R.

Cats have had domesticated humans for roughly 10,000 years.
Goats have been domesticated for at least 10,000 years.
Dogs have been domesticated for at bare minimum 15,000 years.
People have had their favourite pet animals for much longer than you think.