It's very difficult to give a simple one size-fits-all answer to this question... there are several factors that have to be considered...
...some of them are obvious:
-body type and structure (somatype)
-limb ratios relative to each other and the spine, pelvis, clavicles
-wrist circumference
-ankle circumference
-extent of cold adaption in the morphology of the body
-finger lengths relative to each other
...and some of them latent:
-genetic predisposition
-hormone responses
-training drive
etc. etc.
A better guideline would be in terms of attainable strength levels:
80% of adult males should be able to complete (in good form) a max single in the bench/squat/deadlift with approx. 300/400/500 lbs respectively with three years of concerted training and diet.
Another 10% of adult males will reach this level within three to five years training, and approx 10% will be unable to attain this level of strength.
It's because people don't know how to accurately assess their bodybuilding/strength potential (ie: don't know how to objectively assess the "obvious" factors listed above) that discussions of maximum natural potential quickly degenerate into "everyone over 140 lbs is on steroids" hysteria.
Skip La Couer, John Hanson and Jeff Willet are good examples of what can be achieved naturally.
The Luke
