Using research for civil disobedience: C.U. Ariëns Kappers

A disclaimer: This is a summary of one account of C.U. Ariëns Kappers and his role in the events of World War II (WWII) in the Netherlands. There are more critical accounts out there, valid for their own reasons. The present summary attempts to present a view set in a historical context with minor interjections to be consistent with modern standards.

Cornelius Ariëns Kappers in 1930 in Beirut. Taken from Zeidman & Cohen (2014), figure 1.

The historical (and too often modern) treatment of marginalized social groups in scientific research has been flawed at best and grotesque and cruel at worst. Most students who take a science or social science class will learn of the horrors of the Holocaust and WWII. Sometimes missing from this conversation is the “scientific” case used to justify the abuses suffered by Jews and others deemed to be enemies of the Nazi regime. The idea was that these individuals needed to be confined and exterminated based on the well-documented inferiority of their race by centuries of “science” (for an example, see the Victorian practice of phrenology). The present historical account of a Dutch neuroscientist – C.U. Ariëns Kappers – by Lawrence Zeidman and Jaap Cohen (2014) is one that highlights a desperate attempt to use science for the opposite goal: to suggest that no race is inferior and that there is no justification for the rampant abuse afforded to the Jewish people.

C.U. Ariëns Kappers: The Scientist

Ariëns Kappers demonstrating a skull measurement in Beirut, 1929. Taken from Zeidman & Cohen (2014), figure 3.

In his anthropological research, Ariëns Kappers characterized minute racial differences and similarities using the cephalic index — a ratio of the maximum head width and maximum head length, multiplied by 100. Originally used to model population migration patterns of pre-historic human ancestors, post-WWII this index became linked to racist scientific practices and fell out of use. The cephalic index has resurfaced in recent decades in anthropological research as a tool to study trends in human evolution as well as a diagnostic tool to monitor infant cranial formation (Likus et al., 2014).

In a showcase of human diversity and variability within data, Kappers’ reporting practices parallel the modern trends in that he presented frequency curves and distributions of data rather than group mean comparisons. He felt that this practice preserved within-group differences and variance, which allows for a more complete picture of the data. Along with his dedication to scientific transparency, he was also an advocate for absolute accuracy in scientific language and the necessity to not equate race with ethnicity or religion. His research led him to speak out against the scientific classification of “Semitic races” that would later lead to the segregation and removal of Jewish people during the Holocaust. When antisemitism began gaining mainstream popularity in Europe, Kappers was quoted as:

The expression “Semitic race or races” often used [to describe Hebrews, Arabs, and other Middle Eastern groups] is one of the most inappropriate expressions occurring in anthropology, just as confusing as the word Aryan. Although taken in the biblical sense it means to indicate people that are mutually related (being all descendants of Sem), practically the term only indicates people that speak a Semitic language . . . What then is the anthropological meaning of the expression “Semitic people”? None at all.

Ariëns Kappers & Parr, 1934, p. 43

Kappers dedicated a lot of energy in the 1930s-1940s demonstrating differences between Ashkenazi and Sephardic Jewish people using the cephalic index. This was both contradictory and clarifying to his earlier stance on the lack of differences between races based on religion and those based on physical characteristics. Historically, these branches of Judaism are characterized by religious customs and where the people lived (Eastern Europe for Ashkenazi, the Iberian peninsula and Northern Africa for Sephardic Jewish people).

Kappers, along with Willem Klein (of Ashkenazi descent), Elsa D’Oliveira (of Sephardim descent), and his nephew Hans Ariëns Kappers, conducted extensive research in Amsterdam on differences among Dutch Ashkenazim and Sephardim Jewish people. In the beginning, this research was used to assist in “proving” partial Jewishness in those registered as full Jews and later used to save Sephardic Jews from deportation. This research was also used to prevent certain Jewish people from being deported to the Nazi work and death camps.

C.U. Ariëns Kappers: The Advocate

When fascism and antisemitic ideals began gaining widespread popularity in the 1930s, Kappers quickly spoke out against the discriminatory trends with many other academic professionals. Of the many practices banning Jewish people from participating in society, the one that most directly affected Kappers, was the ban of Jewish students from enrolling and graduating from universities. Along with 40 other professors, he participated in founding a committee dedicated to assisting Jewish university students in completing their studies. Among Kappers’ own students, his 9th student, David Moffie, was the last Jewish student to obtain a degree at the University of Amsterdam during the war. In fact, David Moffie defended his dissertation and received his degree on the last possible day before the Nazis banned all Jewish students from being awarded degrees (see adjacent figure).

Ceremony in the Senate Chamber of the University of Amsterdam on September 18, 1942. Leftmost across the table is supervisor Prof. Dr. C. U. Ariëns Kappers and second from the right is David Moffie, the last Jewish doctoral student at the University of Amsterdam during the occupation. Taken from Zeidman & Cohen (2014), figure 5.

Kappers continued teaching courses at the University of Amsterdam until 1944 when all courses were suspended by the occupying German government. Members of the Dutch resistance criticized this practice because the students who were still able to attend courses were those who had signed loyalty oaths to the occupying government. Members of the resistance viewed this as working with the enemy, but Kappers defended this decision by arguing that he needed to stay on the good side of the occupying government to assist Jews in the official legal system.  

Possibly Kappers’ most well-known actions during the war (for better or worse) were his attempts with Dr. Arie de Froe (1907–1992) to exempt the Portuguese Sephardic Jews from deportation. Drs. de Froe and Kappers presumably met while they were working in neighboring institutes, and both were involved with anthropological and anatomical research. When Germany first began occupying the Netherlands, the Nazis required all Jews to register as either “full Jews” (whose “grandparents included 3 or more full Jews by race”) or “partial-Jews” (Mischlinge, who had at least one Jewish grandparent). Several members of the Jewish community registered as “full Jews” even though they were only “partial Jews” out of solidarity. When the Nazi government began deporting all the registered full Jewish people to concentration camps, many people began attempts to prove their “partial” Jewishness to avoid these deportations.

This was a formal process conducted through the Nazi court system and was often overseen by lawyers who helped compile evidence of their clients’ partial Jewishness. This evidence included letters from Aryan fathers claiming to have had affairs with Jewish women, found baptism records, and medical evidence.

Distributions of cephalic indices from Ashkenazim (continuous curve) and Sephardim populations (dotted curve). Taken from Zeidman & Cohen (2014), figure 4.

Using the cephalic index work, Drs. Kappers and de Froe provided the fabricated aforementioned medical evidence that helped save 200-300 Jewish (Ashkenazi and Sephardic) people from deportation. Kappers, de Froe, and assistants would measure the cephalic index of someone petitioning for leniency and create a misleading claim that it fell outside of the range typically seen in full Jewishness individuals (for example, if one’s cephalic index fell outside of the curves seen in adjacent cephalic indices figure). These deeds came with tremendous risks.

Beyond these individual reports, Kappers and de Froe attempted to prove that all Portuguese Sephardic Jews in the Netherlands should be exempt from deportation. The lawyers, researchers, and Jewish representatives involved in the case used evidence from Kappers’ Introduction to the Anthropology of the Near East (1934) that showed Sephardim and Ashkenazim people have different peaks in their cephalic index curves (see the adjacent figure). If successful, this attempt would have exempted 4,303 Portuguese Sephardic Jewish people from deportation.

Unfortunately, in the end, this attempt was a failure due to the extreme antisemitism displayed by the Nazi occupiers. This attempt also left a lasting unpleasant reflection on Kappers and de Froe. Hoping for an increased chance of appealing to the Nazi decision-makers, the reports they wrote and submitted for review used the same antisemitic logic to emphasize the differences between the Sephardim and Ashkenazim. These antisemitic reports, along with statements by Kappers suggesting that the rights won in America by African Americans were less-deserved than the rights of Jewish people in Europe, have left a black mark on Kappers’ historical reputation.

After the war, many critics claimed that Kappers’ and de Froe’s reports did more harm than good to the image of the Jewish people and upheld harmful stereotypes. Those involved defend their actions by using the defense that “all is fair in war” and that any attempt to save a life during this time was worth the negative backlash.


Dr. C. U. Ariëns Kappers died in 1946, only a few years after the war ended. Estimates suggest that Ariëns Kappers’ work and attempts during the war helped save about 300 Jewish people from deportation. Prior to the war, Ariëns Kappers contributed significantly to neuroscience and anthropology. His legacy, the C. U. Ariëns Kappers brain collection, can still be appreciated at the Netherlands Institute for Neuroscience in Amsterdam.

C. U. Kappers: Timeline of Events


Likus, W., Bajor, G., Gruszczyńska, K., Baron, J., Markowski, J., Machnikowska-Sokołowska, M., Milka, D., & Lepich, T. (2014). Cephalic Index in the first three years of life: Study of children with normal brain development based on computed tomography. The Scientific World Journal, 502836.

Zeidman, L. A., & Cohen, J. (2014). Walking a fine scientific line: The extraordinary deeds of Dutch neuroscientist CU Ariëns Kappers before and during World War II. Journal of the History of the Neurosciences23(3), 252-275.