How come black spots appear on dog's tongues as they age?

When my dog was four I noticed a black spot on the back of her tongue. I already knew this happened to dogs but I want to know why.

The dog has been licking itself for years is #1.
But also, it just happens to dogs. Not all dog have this though.

It's perfectly normal to have black spots on your dog's tongue. Just try some normal oral hygiene activities like brushing their teeth regularly, cleaning their tongues with wipes, giving dental treats, etc. You can buy these oral grooming products from petcarerx or petco or from your local vet's clinic.

However, if you still notice these spots even after doing all the things mentioned above, it's good that you consult your vet about this. If the spots have come up in recent times, the Vet may know exactly why this has happened.