From the wonderful world of Wikipedia, I learned that the Shiba Inu is among 14 ancient dog breeds. However, if you dig into the source of the study, it gets even more interesting. The study was done by Parker et al. published in the journal Science in 2004.
Here are a couple of pictures from the study. I cropped out the section of the picture that identified the 14 ancient breeds and their genetic variation from the Gray Wolf. What I conclude from the picture is that the Shiba Inu, Chow-Chow, Akita, and Basenji have less genetic variation from the Gray Wolf than the other ancient breeds.
I'm less sure about how to interpret this next picture. I also don't know what the numbers mean. It looks like the initial break from the Gray Wolf was the Shar-pei and the Shiba Inu/Chow-Chow/Akita. But if you look at the previous picture the Shar-pei seemed to have more genetic variation from the Gray Wolf, so I'm not sure how to reconcile that with this tree, which shows that the Shar-pei was part of the initial break from the Gray Wolf.
Hence, although I am confused about the status of the Shar-Pei, I conclude that Shibas are at least in the top 5 most ancient dog breeds.
Why does all of this interest me? I like to think that Shibas are special, as I'm sure most dog owners like to think their dog's breed is special. And this study offers more conclusive evidence of the Shiba really being unlike other dog breeds. It makes me feel better about being ignored by my dog. And makes me feel that I'm not such a bad dog parent when Loki does not have the innate willingness to please its human owner that other dogs seem to possess.