I only have 28 teeth even without having my wisdom teeth removed. I still have 2 of my baby teeth because I just didn't have any permanent teeth grow there. I think most mammals have around 20-30 teeth so guinea pigs are about average.
I have 31 teeth! Only three of my wisdom teeth have ever grown - I've had them in since I was 16 (Ack - that's been 16 years then!). There is no trace of a fourth one. My mother is the same. As humans are evolving to no longer grow wisdom teeth is a bit of a joke in our family that my Mom and I are 'evolutionarily more advanced'.