Did they monkey around in prehistory? (6)

I believe the answer is:

apemen

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'prehistory?' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'did they monkey around in' is the wordplay.
'did they' becomes 'amen' (I can't justify this - if you can you should believe this answer much more).
'monkey' becomes 'aper' (I've seen this in another clue).
'around' indicates the central letters.
'in' is an insertion indicator.
The middle of 'aper' is 'pe'.
'amen' going around 'pe' is 'APEMEN'.

Can you help me to learn more?

(Other definitions for apemen that I've seen before include "Extinct human ancestors" , "Our predecessors" .)

I've seen this clue in the Evening Standard.

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