I would say the normal would be a base point somewhere in the past before we noticed the extreme changes in climate, say 1950?
As for the interglacial period, yes, that is the common theory but the science is showing that the mass release of co2 is changing that cycle and rather than moving into a cooling period, we are moving into a warming period. So bucking the trend over the past few hundred thousand years.
Ultimately we will only know if these hypotheses are correct in the future ( I’m talking possibly millennia not decades).
How do you know that the current changes are extreme?
You need to define your base line parameters.
You cannot use simple temperature statistics gathered over less than a hundred years to draw meaningful conclusions over climate change influences over millennia.
There are just too many other variables
If you are going to apply very limited data to global events on a scale that’s measured in tens of thousands of years, then you really need to define your parameters.
This the climate change lobby resolutely refuses to do.
We’ve only been measuring and plotting climate for a couple of decades and most of the planet is not measured at all.
Yet current levels of accuracy in spot measurements and values are being extrapolated to produce global trend maps which just cannot be verified.
As for Interglacial period being a theory, it has a sound basis in observed facts, we know that the ice ages occurred and we know when they started and when they ended, so not so much a theory as an accepted scientific fact.
As is the fact that the global climate has been warmer too.
And life on earth didn't end, it adapted, to even to the most extreme events.
Where life couldn’t adapt and survive it lurked where it could, bided its time and re-colonised.