Reversion and reversal

[MinistrChleba]

Hello,
reading Nicholas Carr's The Shallows, I stumbled upon the following quote from H. G. Wells:

“His [=mankind's] social life, his habits, have changed completely, have even undergone reversion and reversal, while his heredity seems to have changed very little if at all, since the late Stone Age.”

What does he mean by "reversion and reversal" and what is the difference between the two? Does reversion here mean a step back and reversal a change of direction? Or is it some kind of an idiom?
Thank you.

 

[Chez]

Yes, I think you have the correct meanings.

reversion is from 'revert' (to go back to – take a step back)

reversal is from 'reverse' (to change to the opposite direction)

Admittedly there's not a huge difference between them in this context.

 

[MinistrChleba]

Ok, thank you.