«JOURNAL OF CONTEMPORARY ANTHROPOLOGY RESEARCH ARTICLE VOLUME II 2011 ISSUE 1 On the Antiquity of Trisomy 21: Moving Towards a Quantitative Diagnosis ...»
VOLUME II 2011 ISSUE 1
On the Antiquity of Trisomy 21:
Moving Towards a Quantitative Diagnosis of Down Syndrome
in Historic Material Culture
John M. Starbuck
Ph.D. Candidate Department of Anthropology The Pennsylvania State University University Park, Pennsylvania Copyright © John M. Starbuck
On the Antiquity of Trisomy 21:
Moving Towards a Quantitative Diagnosis of Down Syndrome in Historic Material Culture John M. Starbuck Ph.D. Candidate Department of Anthropology The Pennsylvania State University University Park, Pennsylvania
Starbuck: On the Antiquity of Trisomy 21 19
INTRODUCTIONDown syndrome was first described in the medical literature by John Langdon Down in
1866. During this era individuals with cognitive impairment (i.e. mental retardation) were often referred to as ―idiots‖ and ―imbeciles‖ and rarely differentiated into subcategories based upon differential diagnoses. Using a hierarchical racial classification system that was popular during his age, John Langdon Down noted the resemblance of facial features among individuals with Down syndrome and individuals of Mongolian descent (Down 1866; Volpe 1986). Down also noted the characteristic facial appearance and shared phenotypic features of unrelated individuals with Down syndrome in the following: ―[…] when placed side by side, it is difficult to believe that the specimens compared are not children of the same parents‖ (Down 1866: 260). Based upon these observations Down determined that individuals with Down syndrome differed from other types of individuals with cognitive impairment and labeled these individuals as ―Mongolian idiots‖ or ―mongoloids‖ (Down 1866:260-261). Although other authors (e.g.
Esquirol and Seguin as cited in Stratford 1996: 3-4) may have described individuals with Down syndrome before Down’s publication in 1866, Down is credited with being the first person to group together individuals with Down syndrome based upon their phenotypic similarities to define a subcategory of individuals with cognitive impairment (Megarbane et al. 2009; Stratford 1996; Pueschel 2000).
The hierarchical racial ladder of Down’s era viewed the races of mankind as being fixed and definite, with Caucasians being superior to all other races and Mongolians being at the bottom of the ladder (Volpe 1986). Although Down’s ―Mongolian idiot‖ and ―mongoloid‖ labels would be viewed as racist today, the use of these terms was a consequence of the prevailing ideas of racial hierarchies from his era (Volpe 1986). By combining this interpretative framework with his phenotypic observations of individuals with Down syndrome, Down made an argument for the ―unity of the human species‖ (Down 1866). Down reasoned that if a disease can break down supposedly ―fixed‖ racial barriers by producing a Mongolian-like child from non-Mongolian parents, then the racial categories of mankind are likely not fixed at all and quite variable (Down, 1866:262). This was an unpopular opinion at the time of Down’s publication. Interestingly, if Down had not favored this hierarchical racial classification system for understanding differences between individuals with cognitive impairment, it is likely that it would have taken much longer for medical scientists to classify Down syndrome as different from other forms of cognitive impairment.
After Down’s classification of Down syndrome many investigators attempted to document exactly how individuals with this condition differ. Several studies have determined that individuals with Down syndrome differ phenotypically from individuals who do not have Down syndrome in many ways. General differences include the following: almond-shaped eyes (Shuttleworth 1886; Oliver 1891), oblique palpebral fissures (Muir 1903), an open-mouthed facial posture that may include a protruding tongue, broad and stocky necks, obesity (Pueschel 2000), short, broad, and small hands and feet (Fraser and Mitchell 1876-7; Chumlea et al. 1979), hands may have a simian palmar crease (Hall 1966), inward curving little fingers (Smith 1896;
Muir 1903), a wide space between first and second toes (Pueschel 2000:55), and a high frequency congenital heart defects (Garrod 1898). Before karyotyping was possible, individuals with Down syndrome were usually diagnosed based upon differences in craniofacial characteristics. Osseous craniofacial differences include the following: brachycephalic-shaped heads (Fraser and Mitchell 1876-7) small or absent nasal bones (Jones1890; Greig 1927a), an underdeveloped mandible and maxilla (Benda 1941), flat or concave midfaces (Greig 1927b), 20 Journal of Contemporary Anthropology Vol. II (2011), Iss. 1 poor or absent sinus development (Spitzer and Robinson 1955; Roche et al. 1961), smaller palates (Redman et al. 1966), poor or absent tooth morphogenesis and highly variable tooth eruption sequences (Jones 1890; Greig 1927b; Townsend 1987), and reduced rates of craniofacial growth overall (O’Riordan and Walker 1978; von Hofe 1922). Soft-tissue craniofacial differences include the following: prominent forehead (Volpe 1986), epicanthic folds (Shuttleworth 1886; Oliver 1891), a flat or depressed nasal bridge, upturned nose (Jones1890; Greig 1927a), midfacial hypoplasia (Kisling 1966; Frostad et al. 1971), small mouth (Pueschel 2000), folded over upper helix of ear (Hall 1966), poor craniofacial musculature differentiation (Bersu1980), reduced overall facial size (Benda 1941), and a relatively short face (Gollesz 1961) that can be square-like when viewed anteriorly (Fraser and Mitchell 1876-7).
These lists are by no means exhaustive. The facial phenotype exhibited depends on genetic background, type of chromosomal abnormality causing Down syndrome (e.g. non-disjunction, translocation, or mosaicism), age, and sex (Pueschel 2000). The overwhelming consensus is that the craniofacial phenotype of Down syndrome always shows some degree of facial dysmorphology; however, no single phenotypic difference is always present (Pueschel 2000).
In 1959 LeJeune discovered that an extra copy of human chromosome 21 (i.e. trisomy
21) causes Down syndrome (LeJeune et al. 1959); however, Waardenburg inferred this in 1932 (Allen 1974). Chromosome 21 contains about 1.5% of the human genome and has an estimated 300-400 protein coding genes (Gardiner et al. 2003; Hattori et al. 2000; Megarbane et al. 2009).
Specifically, the Down syndrome genotype can occur from nondisjunction, translocation, and mosaicism; however, nondisjunction is by far the most frequent cause of Down syndrome (~95%) (Fisher 1983; Hassold et al. 1993). Trisomy 21 is responsible for causing the abovementioned phenotypic differences by causing a gene-dosage imbalance that disrupts development.
Genetic lines of evidence indicate that the ancestral human chromosome 21 arose 30-50 mya (Richard and Dutrillaux 1998). Interestingly, the condition of trisomy 21 is not limited to humans. In non-human apes chromosome 22 is analogous to human chromosome 21. Humans have two less chromosomes than our ape cousins because of a chromosomal fusion that occurred several million years ago to produce human chromosome 2 (Kasai et al. 2000; Wienberg et al.
1994; Yunis and Prakash 1982). Trisomy 22 is the genetic equivalent of Down syndrome in apes and has been reported in both a chimpanzee (McClure et al. 1969) and orangutan (Andrle, 1979).
Taken together, these lines of evidence indicate that trisomy 21 has an incredibly long history in the primate lineage.
Today we know that Down syndrome is found in all ethnic backgrounds and socioeconomic statuses at a frequency of about 1:700 (Kuppermann et al. 2006; CDCP 2006). A marked maternal age effect has also been noted (von Hofe 1922; Penrose 1951; Hook 1989). On average more than 700 Down syndrome children are born each day worldwide and more than 255,000 individuals with Down syndrome are born each year. Due to improved healthcare, the life expectancy for individuals with Down syndrome has consistently risen from 9 years in 1900, to 30 years in the 1960’s, and to more than 50 years today (Collman and Stoller 1962;
Megarbane et al. 2009), which has resulted in an increase in prevalence (Einfeld and Brown 2010). However, the average lifespan of 9 years in 1900 may have been skewed due to a cultural tendency to institutionalize cognitively impaired individuals during this time period combined with the poor living conditions and developmental outcomes associated with many of these institutions (Stimson et al. 1968; Kugel 1961). It is possible that in some cultures individuals Starbuck: On the Antiquity of Trisomy 21 21 with Down syndrome who did not have severe health problems may have enjoyed a higher average lifespan (Stratford 1982:250-254).
There is debate within the literature about the age of Down syndrome as a condition affecting mankind. Down syndrome is the most common live-born aneuploid condition in humans; however, this condition was not described medically until 1866 (Down 1866). The high prevalence of Down syndrome relative to other genetic anomalies and the length of time it took for this condition to be described medically has caused some authors to question whether or not Down syndrome is a relatively old or new condition in humans (Mirkinson 1968; Volpe 1986).
However, Pueschel (2000:11) provides three reasons for why Down syndrome was not recognized as a clinical entity before 1866: 1) prior to the 19th century few physicians were interested in children with developmental disabilities, 2) many diseases and disorders were more prevalent then, which would have overshadowed the occurrence of Down syndrome, and 3) at this time period only half of the female population survived past the age of 35, which would reduce the number of late aged pregnancies that are more likely to produce a child with Down syndrome. Furthermore, Richards (1968: 353-354) pointed out that population size, population age-structure, and infant mortality probably heavily influenced the prevalence (i.e. number of babies surviving) of Down syndrome and precluded medical science from recognizing this condition earlier. However, medical conditions have frequently been identified in historical material culture (Salter 2008). Phenotypically- and historically-speaking the condition of Down syndrome may be represented in skeletal material and several forms of material culture from various populations that are both spatially and temporally discrete. Within this paper I provide an extensive list and description of skeletal remains and material culture that may depict Down syndrome (Appendix A) and, where relevant, I discuss debates within the literature about how likely such qualitative diagnoses are to be correct. I then make suggestions for ways in which a quantitative diagnosis can be made to either strengthen or weaken the qualitative arguments for or against the diagnosis of Down syndrome in historic material culture.
SKELETAL MATERIALSRI-3 skeletal remains (circa 5200 B.C.) Walker and colleagues (1991) published an
on 7200 year old skeletal remains (SRI-3) from Santa Rosa Island, CA, which were found in a Native American cemetery. This
individual’s sex was estimated to be female. Cranial characteristics included the following:
metopism, very wide interorbital distances, a low and wide nasal aperture, reduced auricular height, a flat cranial base, small teeth, and a dysmorphic peg-shaped third molar. Overall, the dimensions of the mandible, palate, and cranial vault were similar to those of other SRI-3 females. Walker and researchers also recovered a femur, a fragmentary os coxa, and three cervical vertebrae (C1-C3), many of which were also unusually small. Walker and colleagues noted that several of these skeletal characteristics are consistent with those found in Down syndrome; however, given the lack of a representative skeletal collection of individuals with Down syndrome, this diagnosis was not conclusive. Unfortunately, Dr. Walker’s untimely passing has prevented more detailed publications about this individual, but Dr. Della C. Cook from Indiana University intends to publish further on these skeletal remains (personal communication). If this individual had Down syndrome it would be the oldest recorded and most complete historical skeletal material with this condition to date.
22 Journal of Contemporary Anthropology Vol. II (2011), Iss. 1 Tauberbischofsheim skull (circa 550 B.C.) Czarnetski and colleagues (2003) briefly describe 2550 year old craniofacial skeletal remains from a burial site at Tauberbischofsheim, Germany. This individual’s sex was estimated to be female, and she was estimated to be 18-20 years of age at the time of death. Unfortunately a detailed description of the skull was not provided. Also, while the authors provided a picture of a Down syndrome skull, it is not clear whether or not the picture provided is of the skull in question (Czarnetski et al. 2003).