How can we define units of measurement when we don have anything to compare them against?
Apart from the kg all SI base units are fixed to natural constants. For example the second is defined by so many oscillations of Cs, the metre as the distance light travels in 1/c seconds in a vacuum (c is speed of light) the kg is defined by a metal bar kept in Paris SI derived units are derived from the 7 base units. You mention alcohol which is defined using the gram. Also if you note it gives an average amount of units that should be drank. This could have been done on people but pigs are also quite similar. Either way that’s the amount for the average person. The two examples you give are both outliers and would be discounted to avoid skew.
