Our experimental design did, in fact, include multiple safeguards to minimize the opportunity for bias to impact our measurements, as described in detail in our Supplemental Text S2, Materials and Methods. The method was designed so that the measurer was blind to what volumes were being produced, so they could not have matched Morton's value even if they tried. I believe that settles your concern.

But for the sake of completeness, I'll mention that we measured every skull three times, and our measurement error is uniformly extremely low (average of 0.35%, see Supplemental Dataset S2 for all values). So the bias you hypothesize would have had to have been almost perfectly consistent across three separate rounds of measurement.

Furthermore, your suggestion that we might have the same racial biases as Morton is indeed far-fetched, not to mention offensive. It could be rebutted at length in many ways, but here's just one. Many of Morton's ethnic categories are unrecognizable to most Westerners today, because the way people categorize groups changes over time. For example, have you heard of Midianiates, Amboynese, Kanakas, or Hovahs (to name just four of many)? Yet you suggest that we would not only be familiar with these groups, but would somehow have the exact same bias for/against them as Morton did over 150 years ago? Far-fetched is putting it mildly.