Academic journal article Pre- and Peri-natal Psychology Journal

Is Colic a By-Product of Exterogestation?

Academic journal article Pre- and Peri-natal Psychology Journal

Is Colic a By-Product of Exterogestation?

Article excerpt

ABSTRACT: Colic is a disorder of early infancy marked by excessive amounts of loud, persistent crying. Lesser amounts of crying are considered normal in infants. Neither the crying of colicky infants nor the baseline crying of normal human infants have any homologue in the vocal behavior of other mammalian infants. This human-specific cry continuum may reflect a human-specific discomfort continuum which is function of the general immaturity of human neonates. Such immaturity may be the result of selection for altricial birth forced by cephalo-pelvic incompatibility during birth.

The medical literature on infant colic includes enough diversity, discrepancy and obscurity to resist comprehensive summary in a few sentences. However, since the more obvious and recurrent features of this discourse may be the ones that yield the most insight under scrutiny, a brief outline of these may be useful:

1. Colic in human infants is a disorder (a deviation from some conceptualization of "normal"). Its most salient symptom is also its only consistent symptom-loud, prolonged, inconsolable crying (Barr et al. 1992). This crying is a source of stress for caretakers. It is perceived by caretakers to signal discomfort experienced by the infant (Forsyth, 1989; Geertsma & Hyams, 1989)

2. Colic exists in relatively high frequency in the countries which attempt to measure this statistic. Published estimates suggest that 10-40% of otherwise normal infants have colic (Hide & Guyer, 1982; Illingworth, 1954; Lothe, 1989).

3. Colic is developmentally self-limiting. It generally disappears by the time an infant reaches 3-4 months of age (Illingworth, 1954; Taylor, 1957; Weissbluth & Weissbluth, 1991).

4. Although difficult to ignore, colic is also difficult to distinctively diagnose. Prolonged, loud crying is also found in non-colicky infants. Barr et al. (1992) conclude that colicky infants differ principally in the duration of cry bouts although Lester et al. (1992) propose there is a difference in cry quality. A widely accepted definition proposed by Wessel et al. (1954) distinguishes colicky infants from normal infants on the basis of quantitative (but not qualitative) differences in cry behavior.

5. An array of suspected "causes" have been proposed and investigated. Lothe (1989) sorts these into the following categories: gastrointestinal; allergenic; hormonal; psychosocial; cerebral immaturity and "miscellaneous". Despite 50 years of discussion in the medical literature, both the etiology and the cure of infant colic remain elusive (Hewson et al., 1987; Hyams et al., 1989; Lothe, 1989; Stahlberg, 1984).

In the on-going dialogue about infant colic, the evolutionary perspective has not been prominent. The current repertoire of proposed causes all share the property of being relatively "proximate" in nature. This paper will explore the value of developing an explanation for infant colic at the level of "ultimate cause" (i.e. an explanation which references natural selection and adaptation over an evolutionary timescale).

PROXIMATE CAUSE AND ULTIMATE CAUSE

In a chapter entitled "The dual nature of causation in biology," Goldsmith (1991) suggests that Darwin's most fundamental accomplishment was "to enlarge for all time the concept of scientific explanation." By providing a naturalistic explanation for the adaptative design of organisms, Darwin capitalized on the conceptual potential of considering the expansive time frame we now know as the geological time-scale.

Prior to Darwin, causal relations in biology were established within a time frame that was more in keeping with ordinary human experience. To say that colic is "caused" by an "allergic reaction to cow's milk" or by "parental mismanagement" is to deal with a relatively short-term relationship between one or more precipitating events and their consequences. To such explanations of "proximate cause" Darwin added the complementary kind of explanation that has come to be known as "ultimate cause. …

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