Strange problem seems to indicate sterial earth
Radium radioactive alpha beta and gamma rays 1 part per trillionth in earths crust now
Halflife approx 1600 years.
.that comes out to septillion times more radium 128 thousand years ago
therefor the earth was like a reactor core a million years ago.
Unless halflife is incorrent (unlikely)
The amount of radium would have doubles thousands of times long before neandrothol existed
You are assuming a constant half-life over a VERY LARGE period of time. Are you SURE about this assumption?