In its August 2007 review of flooring, Consumer Reports said this about solid wood flooring: "But ... all tend to dent."
In the rating table, they state that prefinished solid wood was "mostly oak, typically nailed to a subfloor, and all were 3/4" thick."
Red oak has a Janka hardness rating of 1290; for white oak, it's 1360. Hard maple, rated at 1450, is only about 9% higher than average of the two oaks.
So why can bowling alleys, typically constructed of maple, withstand at the approach end the extreme abuse of dropped 14-16-pound balls so well while CR claims that all solid wood flooring tend to dent (even under the relatively less severe conditions in a typical household)? Thickness can't be the answer, because dents are surface phenomena. I can't imaging thickness greater than 1/2" inch being any more dent-resistant.
As an aside, the report also said engineered wood "dents easily." This makes some sense; if you put a thin hardwood veneer over a relatively soft under layer (as an absurd example, balsa wood), the veneer won't have any support.