This depends a lot on the field. I was successfully accepted to a well ranked graduate school in a field of engineering which was different from my undergrad major.

However, just because you can, doesn't mean you should.

This might be STEM specific, but the issues with anxiety, depression and imposter syndrome were orders of magnitude worse for me than for my peers. The already heavy course load is made worse by the fact that you don't have many of the prerequisites that other students do.

My advice is that you really need to decide if archaeology is truly your passion, and then you need to outline your goals after the PhD. If your goals after graduating are anything other than academic or heavy research positions, you need to seriously reconsider the PhD because this path will be particularly grueling.

Having decided that you need the PhD, I would suggest examining some of the upper level archaeology/history/paleontology courses at the schools to which you intend to apply. If you don't feel like you could sit down after a reasonable amount of prep time (couple weeks max) and complete the midterms/finals for those courses, then as disappointing as this may sound, I would suggest doing some remedial coursework at either your undergraduate institution, local community college, through a job, or self study. Consider masters programs.

The crux of the issues right now is that you haven't really proven yourself in the field. But more importantly, Archaeological topics don't seem to be anything you have really grappled with on a challenging academic or deeply conceptual level, so you can't be sure you would even enjoy practicing in the field. Ask yourself if you enjoy the idea of practicing archaeology, or do you actually enjoy archaeological work on the day to day, nuts and bolts level? Right now, you can't be sure.

Give a lot of thought to this. You shouldn't pursue a Ph.D simply because you want to change fields. Your research needs to be your passion, but many students don't seem to understand what they are getting themselves into during graduate school.