Green’s Dictionary of Slang

natural-born man n.

also natural man
[the premise is that a ‘natural’ person is not hidebound by social conditioning etc.]

(US black) a ‘real’ (i.e. heterosexual) man, a good lover, an honest, unpretentious person.

[US]R. Fisher Conjure-Man Dies 192: ‘He was sittin’ up in that chair talkin’ pretty lively, like a natchel man.’ ‘Yea, but he ain’ no natchel man—he’s a conjure-man.’.
[US]B. Jackson Get Your Ass in the Water (1974) 168: Monkey lay down there with his nuts in the sand, / he said, ‘Let me get up,’ he said, ‘And I’ll fight you like a natural man.’.
[US]B. Jackson Get Your Ass in the Water (1974) 178: If you let me get my nuts up off this sand [...] I fight you like a natural man.
[US]E. Folb Runnin’ Down Some Lines 149: Many of the same young women [...] indicated an attraction for the ‘natural-born man,’ one who smoked, drank, raised hell, gambled, and womanized.