Several posters have discounted the idea of a variable-radius earth as ridiculous because there is an accepted Pangea paradigm for which there is evidence. But the evidence for Pangea also applies to a smaller Earth. And yes there are plates and tectonics. However how did they get there? I suggest the shrinking Earth is or was the prime driver of subduction.

Certain features of a smaller > larger > present Earth otherwise hard to account for are explained 5by my idea.

These are primarily

Why all the old continents fit together to form a sphere (smaller)

Why giantism flourished on Earth (larger)

In order to conserve angular momentum the smaller Earth must have had shorter days, and the larger Earth longer.

Orbit would be unchanged, even if some mass was lost as Hydrogen

Now, is there any evidence that refutes what I suggest has happened?

Is not a deal breaker... but if there is one I will concede defeat

PS

I suspect at the root of all this is the reversible reaction n+v=p+e and that High Temp/Pressure and possibly Fe catalyst pushes the equilibrium to the left and supplies activation energy. Whereas, at the surface of the Earth with lower temp and pressure and density neutron decay is observed with a half-life of about 10.3 minutes.