Re: Heard a joke -- Urea concentration
The article basically states (with methods, data, and results) that urine kills bacteria and it only seemed to be positively correlated to urea concentration.
So if you eat a lot of meat and don't drink much water, your urine would be an antiseptic. I'd imagine urine on the Arabian peninsula could get quite concentrated, so that fits.
The "osmolality" part refers to saltiness (or dissolves stuff in general) and they say that doesn't help nor hurt and neither does ammonia.
But if the urine has the urea which is converted to ammonia (cat pee smell) then it's not as useful.
SOURCE: BST Chemistry Education, graduate studies in (oligopeptide) biochemistry