Birth defects among Caquintes
I am in Atalaya (Ucayali, Peru) returning to my field site after a week and a half of vacation in Lima, Caraz (Ancash), and at Gocta Lodge, situated in the village of Cocachimba in the Amazonas region north of Chachapoyas. This post deals with a topic that I only inadvertently began to find out about during a brief stay in the Caquinte community of Kitepámpani last month and earlier this month. It concerns the presence of a collocation of birth defects across at least three generations of one extended Caquinte family group. I want to write anonymizing the names of the individuals involved to see if other linguists have encountered similar phenomena in the communities in which they work.
First, some brief background: Caquintes are a small population of some 400-500 individuals spanning the mountains that separate the Tambo and Urubamba river drainages in the Cusco and Junín regions of southeastern Peru. Until the late 19th century, they lived at the mouth of the Pogeni River, a right-bank tributary of the Tambo; from there they fled Asháninka raids, ultimately settling near a mountain named Tsoroja in the headwaters of the same river. They continued to suffer from Asháninka (and Yine) raids at least through the 1920s. In the 1950s they began migrating into the headwaters of the left-bank tributaries of the Urubamba (Cusco), specifically the Ageni and Yori, which meet to form the Mipaya at Kitepámpani, which ultimately drains into the Urubamba. This in part seems to have been driven by the attempts of missionaries working in the Tambo drainage to settle Asháninkas and Caquintes together on the Pogeni. At least the lower Yori was occupied by Matsigenkas at the time, who left the area fearing attacks by Caquintes. However, at least two Caquinte men (Shankenti and Koshanti) took Matsigenka wives. There seem to have been four extended households in the region at this time: Shankenti (on the Tipeshihari, a stream emptying into the Ageni) and Taataki, Mohina, and Meshinantsi (all on the Yori). Since this time, Caquintes have come to intermarry in large numbers with Matsigenkas and Asháninkas. Cross-cousin marriage is preferred, and in an overwhelming majority of cases is actually practiced; polygyny was not infrequent, and co-wives were preferrably (classificatory) sisters.
The birth defects consist of polydactyly (six fingers and six toes),
sterility in women (however, they are said to menstruate), and
occasional poor vision and mental disability. A tree summarizing the
defects is shown below: triangles are men, circles are women, double
lines are marriages, shadedness denotes affected individuals, crosses
indicate deceased individuals, and checks indicate living individuals.
Each individual has a unique letter for the discussion below.
B was a woman first married to C; upon his death she married A. A's
father is known, but C's father is not, although it is possible given
patterns of remarriage upon death that A and C were brothers (either
full, half, or classificatory, i.e., parallel first cousins). Two of B's
daughters with A (D & E) were affected, and they died either as
children or young adults without marrying. Two of B's other daughters (G
& I), half-sisters to each other, married H. This was, at least on
one side, an incestuous marriage by local practice, since H's mother was
a sister of B; however, nothing is known about H's father except his
name, and it is possible that the kinship relation was redefined via a
relation on this side of H's family so as to make the marriage not
incestuous. Next, G had several children with H (not all listed here),
and at least one daughter (J) was affected; similarly, I also had
several children with H (not all listed here), and none are currently
known to be affected. L & N, two of these unaffected daughters, each
married M: M is L & N's cross-cousin through his mother, but the
children of his cross-cousin through his father. Both L & N have had
several children with M: two of L's daughters and one of N's sons is
affected.
H & M are part of a separate extended family group (that include B) that is well documented; the described birth defects are not present there. This would suggest that the locus of the genetic mutation causing the defects is with A & C. It is commonly understood that descendants of A are the ones affected, but this can't be correct, since Q is not a direct descendant of A. A friend and fellow graduate student at Berkeley has helped me entertain a few different possibilities that might explain the distribution of these defects, although further genealogical (and genetic!) research is necessary. He points out that it is not a simple autosomal dominant trait. (I paraphrase him at various points below.)
1) The trait may be recessive but with a high incidence in the population, much like Ashkenazi Jews are likelier to be carriers of Crohn's Disease. He points out that this is unlikely because all three in-marriers (B, H, and M) would have to be carriers.
2) The trait may be dominant but not perfectly penetrant, in which case the mutation would probably trace back to a possible common ancestor of A & C. He considers this most likely, but ultimately 'unverifiable without sequencing data from asymptomatic carriers'.
3) There might be multiple genes contributing to this collocation of defects.
4) The trait may be recessive on the X-chromosome, and the phenomenon at hand might be part of what are known as 'disorders of sex development' (a name that he points out is controversial). The idea, oversimplified, is that it is possible for an XY individual to be phenotypically female. Different sex organs may develop, including a vagina and uterus (cf. menstruation), but resulting in sterility in apparent women. On this story, all affected "women" are actually genetically XY and sterile, and XY individuals with a penis represent a case of incomplete penetrance; B was the carrier with the original mutation. This explanation can easily be disproved if unaffected men are found to father affected children. The intuition behind this explanation is that sterility seems to be the most prevalent phenotype and that men do not seem to be able to be carriers. He adds that this explanation is not very likely, however.
On his advice I plan to (discreetly) investigate the exact nature of the polydactyly further, and -- much less likely given privacy -- the nature of infertility in women or reduced fertility in men. It will also be useful to know more about the range of approximate ages at which affected individuals die, as well possibly increased rates of miscarriage and infant mortality in potential carriers.
First, some brief background: Caquintes are a small population of some 400-500 individuals spanning the mountains that separate the Tambo and Urubamba river drainages in the Cusco and Junín regions of southeastern Peru. Until the late 19th century, they lived at the mouth of the Pogeni River, a right-bank tributary of the Tambo; from there they fled Asháninka raids, ultimately settling near a mountain named Tsoroja in the headwaters of the same river. They continued to suffer from Asháninka (and Yine) raids at least through the 1920s. In the 1950s they began migrating into the headwaters of the left-bank tributaries of the Urubamba (Cusco), specifically the Ageni and Yori, which meet to form the Mipaya at Kitepámpani, which ultimately drains into the Urubamba. This in part seems to have been driven by the attempts of missionaries working in the Tambo drainage to settle Asháninkas and Caquintes together on the Pogeni. At least the lower Yori was occupied by Matsigenkas at the time, who left the area fearing attacks by Caquintes. However, at least two Caquinte men (Shankenti and Koshanti) took Matsigenka wives. There seem to have been four extended households in the region at this time: Shankenti (on the Tipeshihari, a stream emptying into the Ageni) and Taataki, Mohina, and Meshinantsi (all on the Yori). Since this time, Caquintes have come to intermarry in large numbers with Matsigenkas and Asháninkas. Cross-cousin marriage is preferred, and in an overwhelming majority of cases is actually practiced; polygyny was not infrequent, and co-wives were preferrably (classificatory) sisters.
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| Map of Caquinte Territory (courtesy: Instituto del Bien Común) |
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| Genealogy of Affected Caquintes |
H & M are part of a separate extended family group (that include B) that is well documented; the described birth defects are not present there. This would suggest that the locus of the genetic mutation causing the defects is with A & C. It is commonly understood that descendants of A are the ones affected, but this can't be correct, since Q is not a direct descendant of A. A friend and fellow graduate student at Berkeley has helped me entertain a few different possibilities that might explain the distribution of these defects, although further genealogical (and genetic!) research is necessary. He points out that it is not a simple autosomal dominant trait. (I paraphrase him at various points below.)
1) The trait may be recessive but with a high incidence in the population, much like Ashkenazi Jews are likelier to be carriers of Crohn's Disease. He points out that this is unlikely because all three in-marriers (B, H, and M) would have to be carriers.
2) The trait may be dominant but not perfectly penetrant, in which case the mutation would probably trace back to a possible common ancestor of A & C. He considers this most likely, but ultimately 'unverifiable without sequencing data from asymptomatic carriers'.
3) There might be multiple genes contributing to this collocation of defects.
4) The trait may be recessive on the X-chromosome, and the phenomenon at hand might be part of what are known as 'disorders of sex development' (a name that he points out is controversial). The idea, oversimplified, is that it is possible for an XY individual to be phenotypically female. Different sex organs may develop, including a vagina and uterus (cf. menstruation), but resulting in sterility in apparent women. On this story, all affected "women" are actually genetically XY and sterile, and XY individuals with a penis represent a case of incomplete penetrance; B was the carrier with the original mutation. This explanation can easily be disproved if unaffected men are found to father affected children. The intuition behind this explanation is that sterility seems to be the most prevalent phenotype and that men do not seem to be able to be carriers. He adds that this explanation is not very likely, however.
On his advice I plan to (discreetly) investigate the exact nature of the polydactyly further, and -- much less likely given privacy -- the nature of infertility in women or reduced fertility in men. It will also be useful to know more about the range of approximate ages at which affected individuals die, as well possibly increased rates of miscarriage and infant mortality in potential carriers.
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