Is it Better to Measure a Skull with Seed or Lead Shot? Answer: Neither.

This blog is based largely on text from Chapter 27 of my book, a pdf of which is posted on this webpage. Detailed footnotes and citations are presented in the pdf. The author does not support racism, eugenics, or even the existence of biologically distinct human races. However, to maintain historical accuracy, this blog uses outdated and sometimes offensive ethnic terms found in historic documents. No offense is intended.

In this blog post I will answer a question that has been nagging me for nearly thirty years. In 1986 I measured the cranial capacity (braincase) of some 200 skulls from the Morton Collection of Human Crania. To measure those skulls, I filled them with acrylic plastic balls. However, when Morton measured them in the mid-1800s he used either seeds or lead shot. In 1839, he measured 256 skulls, by his count, with seed. In Crania America he described this seed as “white pepper seed” which was “selected on account of its spherical form, its hardness, and the equal size of the grains. It was also sifted to render the quality still greater.” Some years later, Morton remeasured most of these skull and a few hundred more using lead shot. Morton explained his reason for changing from peppercorn to shot in a notice published in the April 1841 Proceedings of the Academy of Natural Sciences of Philadelphia:

“Morton made some observations on a mode of ascertaining the internal capacity of the human cranium, by means of the tin tube and graduated rod as described by him in Crania Americana…The material hitherto used by Dr. Morton for the purpose of filling the crania, was white pepper seed, which was selected on account of its spherical form, and the general uniformity in the size of the grains… Dr. Morton then tried leaden shot of the size called BB measuring 1/8th of an inch in diameter which being perfectly smooth and spherical of uniform size and therefore not liable like the seeds to variations from packing”

Eight years later, in 1849, Morton published a catalog describing all the skulls in his collection which included a note explaining that:

“All the measurements in this Catalogue, both of the facial angle and internal capacity, have been made with my own hands. I at one time employed a person to aid me in these elaborate and fatiguing details; but having detected some errors in his measurements, I have been at the pains to revise all that part of the series that had not been previously measured by myself. I can now therefore vouch for the accuracy of these multitudinous data, which I cannot but regard as a novel and important contribution to Ethnological science.

It is necessary to add, that the measurements originally published in the Crania Americana were made with seeds, which will explain the discrepancy between the numbers observable in that work and this catalogue. The measurements of the Crania Aegyptiaca having been originally made with shot, require no revision: nor can I avoid expressing my satisfaction at the singular accuracy of this method since a skull of an hundred cubic inches if measured any number of times with reasonable care will not vary a single cubic inch.”

In other words, Morton hired an assistant to measure the skulls, but did not get what Morton regarded as good results. So, he tried to correct this situation by doing all the measurements himself, and also by using shot which he regarded as a better medium for measuring the skulls.

Although Morton was enthusiastic about the accuracy of his measuring technique, later scholars were not as impressed. Later in the 19th century Carl Vogt, agreed with Morton’s overall findings but not Morton’s measuring technique. In 1864, Vogt praised Morton for concluding that whites had larger skulls than black, thus disproving Tiedemann. Vogt dismissed the “erroneous results formerly propagated by Tiedemann,” which “asserted that the cranial capacity of the Negro was not less than that of the European.” Yet, Vogt faulted Morton for not sufficiently compressing the lead shot when filling the skull, which was a technique used by French anatomist Paul Broca (1824-1880). Vogt wrote that Morton’s skull measurements:

“… as well as those of Welcker, were made with small shot, with which the cranium was filled, and shaken until no more could be introduced. Broca has observed, that no exact measurement is obtained by this method, the differences arising when the same skull is measured several times, amounting to from twenty to thirty five cubic centimeters owing to the fact that, in many skulls, some parts of the internal cavity of the cranium rise above the level of the occipital foramen, through which the shot is introduced. Broca, therefore, by means of a long cuneiform instrument, presses the shot in every direction, until no more can be introduced. His results, though comparable with each other present therefore somewhat higher numbers. Again, the skulls examined by the American observers were selected specimens, whilst those of Broca were obtained from disturbed churchyards.”

Simply put, Vogt felt that Morton should have compressed the shot. Vogt also seems to hint that that Morton’s samples were “selected specimens” rather than a random sample exhumed from a grave. Vogt did however reference Morton’s measurements of Malay skulls to refute claims that they were nearly as large as Europeans. So it seems that Vogt supported those of Morton’s findings that confirmed his own conclusions. Indeed, confirmation bias is an indelible part of the human condition.

Vogt proposed that Morton improperly failed to compact the lead shot that he used to measure skulls. A century later, Stephen Jay Gould postulated that Morton did not compact the skulls with shot, but did compact the skulls when he was measuring them with peppercorns. As Gould wrote in the Mismeasure of Man (page 97)

“I assumed that measures by seed would be lower. Seeds are light and variable in size, even after sieving. Hence, they do not pack well. By vigorous shaking or pressing of the thumb at the foramen magnum (the hole at the base of a skull), seeds can be made to settle, providing room for more. Measures by seed were very variable; Morton reported differences of several cubic inches for recalibrations of the same skull. He eventually became discouraged, firing his assistants, and redid all his measurements personally, with lead shot. Recalibrations never varied by more than a cubic inch, and we may accept Morton’s judgement that measures by shot were objective, accurate and repeatable – while earlier measures my seed were highly subjective and erratic.”

Later on the same page, Gould speculated as to how Morton’s seed measurements may have generated different results from the shot measurements. Gould wrote:

“Plausible scenarios are easy to construct. Morton, measuring by seed, picks up a threateningly large black skull, fills it lightly and gives it a few desultory shakes. Next, he takes a distressingly small Caucasian skull, shakes hard, and pushes mightily at the foramen magnum with his thumb. It is easily done, without conscious motivation; expectation is a powerful guide to action.”

In a 1984 PBS Nova program, Gould was filmed explaining that he had reanalyzed “Morton’s data one summer a few years back. And I discovered that his ranking of whites, Indian and blacks was based more on his hopes than any reality of his data.” Gould then went on to accuse Morton of under-measuring black skulls and over-measuring white skulls, saying:

“Morton picks up the skull of a black man. Gee, it looks kind of disconcertingly large, he’s a little worried about it. You pour in the mustard seed, you shake it very gently try to get it to settle, pour it out again. Then you pick up a white skull which is disconcertingly small and you pour in the mustard seed. You take your thumb and you push on the foramen magnum as hard as you can, you push down, you pour some in some more. It’s… it’s not hard. I mean that must have been what happened.”

In the video, Gould can be seen pantomiming Morton using his thumb to push more seed into Caucasian skulls. And also note that Gould referred to “mustard seed,” not white pepper.

It should be noted that neither Vogt nor Gould actually re-measured Morton’s skulls and Gould never even laid eyes on them. So, both of these men were making assumptions. The question I had for many years was: Were these assumptions true? Does lead shot actually generate more reliable measurements than pepper seed?

In 2014, I decided to run a test. I bought a plastic model human skull from a medical supply store. I measured it with white pepper seed, lead shot and some other materials, like millet which was used by Tiedemann. I bought the white a pepper seed at a Korean grocery store. Shot is hard to find and expensive, so I bought used scuba divers’ weights which are filled with shot. I did not sift the shot or any of the seed materials, so my findings are not “lab quality.” Also, I measured the plastic skull and its contents with my kitchen scale. I invite any enterprising undergrad to re-run this test. If I’m wrong, so be it. My results should therefore be viewed as PRELIMINARY. I would however note that I actually have experience measuring skulls and this is not my first time conducting such research.

My methodology was quite simple. I measured the cranial capacity of my skull in three ways with the assumption that I would get three different results.

1. I measured the skull by filling it with material and only shifting the skull from side to side. One must tilt a skull a bit fill it up. My goal was to try to avoid any settling or compaction of the materials. I call this technique “NOT SHAKEN.”

2. I measured the skull by filling it with material and then I shook it to make it settle. But, I did not push my fingers into the skull to compact it. This is the normal way that modern researchers measure a skull, and this was the technique I used for my 1988 paper. I call this technique “SHAKEN ONLY.”

3. I measured the skull by filling it with material and then I shook it to make it settle and then pushed my fingers into the skull to compact it. I call this technique “COMPACTED.”

I then repeated this process using five different materials: White Pepper, White Mustard,
Millet Seed, White Rice, and Lead Shot. I repeated the measurements for each type and technique ten times. I then took all my data and determined a coefficient of variance (CV) for each type of material and technique. CV is a standard statistical measurement. In very broad terms, a lower CV indicates a more consistent measurement. At the end of this blog I have posted my raw data and calculations.

Once everything was finished, I had generated the fifteen CVs that are presented below:

CV – Material, Technique
0.6 – White Pepper, Compacted
0.8 – Yellow Mustard, Compacted
0.9 – Millet Seed, Not Shaken
1.0 – White Rice, Compacted
1.1 – Lead Shot, Shaken Only
1.1 – Millet Seed, Compacted
1.1 – Lead Shot, Compacted
1.3 -Yellow Mustard, Not Shaken
1.4 -Yellow Mustard, Shaken Only
1.8 – White Pepper, Not Shaken
1.8 – White Pepper, Shaken Only
2.0 – White Rice, Shaken Only
2.2 – Millet Seed, Shaken Only
2.8 – White Rice, Not Shaken
3.2 – Lead Shot, Not Shaken

The main conclusion is that shot is not an especially accurate measurement material relative to other materials. Compressing does not give worse or better results regardless of material. Gould’s assumption, which has been unquestioned for decades, has no foundation. If anything, his assertion shows how little he actually knew about the technique of measuring skulls. But then again, his expertise was studying snails. One would never presume that an anthropologist would have any expertise with snails, thus there is no reason that Gould would be an expert on skulls.

Some practical findings of my research were:

1. It appears that compacting the materials when filling a skull with ANY materials is just a bad idea. It put too much pressure on the skull. When I compressed the materials, (regardless of what they were) the material all moved into the face area, where there are more holes. This is also where there are more fine bones. I would not recommend doing this on a real skull because you would end up breaking some of the internal face bones. Gould assumed that Morton employed compression to make white skulls seem larger. But for that ASSUMPTION to be true, Morton had to have been willing to damage his white skulls.

2. Mustard seed is a mess and is annoying to use. It gets all charged up with static electricity and spills out of eye holes and such. I hated using it due to the mess. Also, I had to work to get the last few seeds out of the inside of the skull.

3. Lead shot is difficult to use and could easily damage many skulls. When my plastic skull was full of lead shot it weighed 19 pounds. The largest bowling ball is 16 pounds. A skull is round and has no good handles. I was afraid I would drop it and smash it. The muscles in my arms got sore hoisting it to the scale. Also, for some reason, a few table spoons of shot balls stayed in the skull. I had to shake it rigorously to get them out. My plastic skull had a removable top that was held together by magnets. The skull popped open the first time I filled it with the shot. It spilled all over the floor. So, I had to tape the skull shut. In summary, shot is hard to use and could easily crack both the thicker and thinner bones in a dry skull. Also, shot was just as easy to compact as any seed material. So for me, it had no special benefits the seeds lacked.

4. Rice was easy, but only worked well when compressed.

5. White pepper was easy to use, but only got good results when compressed. That observation suggests that a lab worker would need to practice a very consistent technique which required some training. So, Morton could have been right that his lab tech got inconsistent results.

6. Millet was the preferable material for many reasons. It was not messy at all. It was light weight, thus doing minimal damage to the skull. It was also easy to pour out of the skull. Most importantly, Millet generated a low CV without even shaking it. It was also quicker. In the 1930s, LIFE magazine ran an article of Harvard anthropologist Earnest Hooton. (“Hooton of Harvard,” LIFE, August 7, 1939). A photo on page 61 shows him measuring a skull with (according to the caption) millet, not shot.

In conclusion, Gould’s assumption that shot was somehow a better material than seed is was a false assumption. Also, it is just as easy to compact shot as seed. If as Gould proposed, Morton’s bias led him to unconsciously mis-measure with seed, then how come that strong bias did not affect his shot measurements? Did Morton’s racial bias inexplicably turn off at some point? A more likely scenario, which I have proposed on other blog posts, is that Morton simply lied. His work was riddled with random errors. I think that when his measurements got results he didn’t like, he would just write down something else. Given that he was an overt racist, he would periodically lie to make Anglo-Saxons appear superior to other races. But that is a case of lying, not subconscious bias secretly corrupting his data set. We have to remember that Morton was not a modern scientist, honor bound to publish only those results that are rigorously tested in a lab setting. He was not, nor did he ever claim to be the objectivist Gould said he was.

Gould uncritically accepted Morton’s false claims that the shot was the ideal material for measuring skulls. My research (as seen in other posts on this web site) suggests that Morton conducted his measurements in part to refute the craniological research of Tiedemann who used millet. So, Morton may have sold (or oversold) the accuracy of shot, so as to make Tiedemann look like an old fashioned guy with an outdated technique that should not be trusted. Ironically, my results show that millet is the preferable material, thus supporting Tiedemann’s findings. The way I see it, if the question is asked, “Who is RIGHT about measuring skulls, Morton or Gould?” The answer is, “Tiedemann.”

I reiterate that the research present on this blog should be regarded as preliminary, and I eagerly encourage some undergraduate, or even a high school student, to duplicate it. Until I am proven wrong, I am the only person who has taken on this task. My work, faulty as it may be, is currently the best done to date. It may not be perfect, but at least from my perspective, I finally have a halfway decent answer to a question that has been bugging me for decades.

PDFSeed-Shot Morton_v5

Leave a Reply

Your email address will not be published. Required fields are marked *