[nabilhat]

Betteridge's law applies. It's well understood that hominids experienced tooth decay throughout their evolution. Causes and contributors and rates over time may be up for debate, but the evidentially confirmed fact that our ancestors got cavities is settled.

https://en.wikipedia.org/wiki/Tooth_decay#History

[stjohnswarts]

It's also well understood that our sugar intake is probably 10x what it was before sugar was cheap and readily available and our cavity rate (at least if you aren't brushing) has increased proportionally. I don't think anyone really believes that cavemen never had cavities, just that it was much less common.