International Society for History, Philosophy, and Social Studies of Biology

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THURSDAY, JULY 9  /  15:30 - 17:00  /  DS-1545
Organized session / standard talks
Evolutionary neurology, hereditarianism, and the formation of medical genetics

Stephen Casper (Clarkson University, United States)

The papers in this panel trace a narrative from evolutionary neurology through to the formation of modern biomedicine. As these papers showcase, questions of evolutionary descent and future shaped geneticist science and medicine in modernity and after. Many Victorian scientists and clinicians claimed that the study of the evolution of the nervous system in animals and human beings, nervous diseases, and the hereditary circumstances of both the organ and its pathologies, was central in the political debates of the day. Victorian evolutionary neurology, grounded in comparative anthropology, physiology, and zoology, provided an essential theoretical conception of the structure and function of the nervous system that subsequently framed explanations of, and treatments for, nervous diseases. Nervous diseases, so many argued in the hereditary discourses of the day, made the natural history of human beings manifest. Thus in this way the discovery of new and supposed neurological conditions shed light on the descent of human beings and permitted speculation about their future. Down’s syndrome, in particular, showcased human development, and, by corollary, when no hereditary component was immediately evident, as in cases of epidemic encephalitis, specialists in nervous diseases still sought refuge in the evolutionary morphology of the nervous system to conceptualize symptoms and to re-imagine autonomy. Much was at stake in this discourse, not least the naturalistic foundations of the human and life sciences and the application of those foundations in policy prescriptions and medical practices. Indeed, the subsequent emergence of medical genetics would be highly dependent upon those lines of reasoning even as the science of human genetics would significantly problematize their scientific and ideological assumptions.

Time, deep history, and the evolutionary neurology of nervous disease

Stephen Casper (Clarkson University, United States)

Victorian clinicians, scientists, anthropologists and naturalists were fascinated by the question of how the passage of time left traces of a deeper history in the nervous system of animals and human beings. Following this logic, human nervous diseases could be used to situate human beings in evolutionary time, as those disease states seemed to disinhibit primitive centers that had served long-passed evolutionary descendants. In this way, nervous diseases transcended mere pathology: the excitation and release of primitive functions in unhealthy human beings appeared as evidence of past modes of the species' existence. The language of nervous disease that ultimately sprang from these theoretical conceptions animated the natural history of degenerative, vegetative, and senescent states. Similarly, the comparative zoology of the nervous system situated the organ system in time as well; embryological and comparative morphological studies traced the evolution of the nervous system from lower to complex forms, while physiological experimentation augmented these studies by theorizing the accumulation of inhibitory processes that had advanced the organism's complexity. In this way nervous diseases functioned as natural experiment and metaphor. Evolutionary neurology ultimately provided a powerful methodological, deterministic, and sometimes fatalistic narrative about time and the nervous system, one that came to underpin many of the premises and assumptions of geneticist, eugenic, evolutionary, physiological, and psychological discoveries of the twentieth century.

From evolutionary neurology to genetics: Tracing the deep history of Down's syndrome

Andrew Hogan (Creighton University, United States)

In 1866 British physician John Langdon Down adopted the term Mongolian Idiocy to describe a form of feeblemindedness that he had identified in a number of patients at the Earlswood Asylum. As head of this institution, Down oversaw the clinical evaluation of hundreds of patients. The regular collection of anthropometric data from each got Down thinking about links between physical and mental abnormalities, facilitating his delineation of this disorder characterized by mental deficiency and distinctive facial features. Down felt that the condition gave affected Caucasian children a Mongolian appearance. From this, he inferred that this neurological disorder in some way returned a child of Caucasian ancestry to an evolutionarily more primitive Mongolian state. His interpretation was grounded in a liberal understanding of race for its time, one assuming that all human races were evolutionarily unified, and that the biological boundaries between them could occasionally break down. While the biological basis of Down s theory was largely discredited by other physicians over the coming decades, the viewpoint that this form of feeblemindedness involved some sort of racial reversion influenced eugenic ideas about mental defect throughout the early-20th century. As genetics came to shape understandings of disease, it was proposed that Mongolian Idiocy represented the uncovering of a primitive trait that had largely disappeared from expression, but still existed in the deep history of human genetics. A more clear cut genetic explanation of Mongolian Idiocy was proposed in 1959 by Jerome Lejeune, who identified an extra copy of chromosome 21 in affected patients. While mid-20th century physicians largely moved away from earlier racial understandings of Mongolian Idiocy, I argue that this new genetic etiology continued to reflect conceptions of neurological disease as having a basis in the uncovering of traits that still lurked somewhere in the deep history of the human genome.