Laurence Irving: An Appreciation

The diving reflex and asphyxia: working across species in physiological ecology

Beginning in the mid-1930s the comparative physiologists Laurence Irving and Per Fredrik (Pete) Scholander pioneered the study of diving mammals, particularly harbor seals. Although resting on earlier work dating back to the late nineteenth century, their research was distinctive in several ways. In contrast to medically oriented physiology, the approaches of Irving and Scholander were strongly influenced by natural history, zoology, ecology, and evolutionary biology. Diving mammals, they argued, shared the cardiopulmonary physiology of terrestrial mammals, but evolution had modified these basic adaptive processes in extreme ways. In particular, seals' remarkable ability to hold breath, lower metabolism, produce energy anaerobically, and resist asphyxiation, provided a sharp contrast with terrestrial mammals, including humans. This diving physiology was an extreme elaboration of a general regulatory mechanism that allowed seals and other diving mammals to remain active underwater for extended periods. The decrease in heart rate referred to as bradycardia or the "diving reflex" was highly developed in diving mammals, but also found in less developed form in many other organisms faced by asphyxia. It therefore served as a kind of "master switch" for lowering metabolism in diving, hibernation, parturition, drowning, and other physiological responses involving lack of oxygen. Studying bradycardia unified a wide diversity of physiological phenomena, while also providing a context for contrasting the physiological responses of various species, including humans. Conducted in the laboratory and the field, this research served as a bridge between a comparative physiological ecology focused on non-human species and a human-centered general physiology.

Bergmann's Rule, Adaptation, and Thermoregulation in Arctic Animals: Conflicting Perspectives from Physiology, Evolutionary Biology, and Physical Anthropology After World War II

Bergmann's rule and Allen's rule played important roles in mid-twentieth century discussions of adaptation, variation, and geographical distribution. Although inherited from the nineteenth-century natural history tradition these rules gained significance during the consolidation of the modern synthesis as evolutionary theorists focused attention on populations as units of evolution. For systematists, the rules provided a compelling rationale for identifying geographical races or subspecies, a function that was also picked up by some physical anthropologists. More generally, the rules provided strong evidence for adaptation by natural selection. Supporters of the rules tacitly, or often explicitly, assumed that the clines described by the rules reflected adaptations for thermoregulation. This assumption was challenged by the physiologists Laurence Irving and Per Scholander based on their arctic research conducted after World War II. Their critique spurred a controversy played out in a series of articles in Evolution, in Ernst Mayr's Animal Species and Evolution, and in the writings of other prominent evolutionary biologists and physical anthropologists. Considering this episode highlights the complexity and ambiguity of important biological concepts such as adaptation, homeostasis, and self-regulation. It also demonstrates how different disciplinary orientations and styles of scientific research influenced evolutionary explanations, and the consequent difficulties of constructing a truly synthetic evolutionary biology in the decades immediately following World War II.

Camels, Cormorants, and Kangaroo Rats: Integration and Synthesis in Organismal Biology After World War II

During the decades following World War II diverse groups of American biologists established a variety of distinctive approaches to organismal biology. Rhetorically, organismal biology could be used defensively to distinguish established research traditions from perceived threats from newly emerging fields such as molecular biology. But, organismal biologists were also interested in integrating biological disciplines and using a focus on organisms to synthesize levels of organization from molecules and cells to populations and communities. Part of this broad movement was the development of an area of research variously referred to as physiological ecology, environmental physiology, or ecophysiology. This area of research was distinctive in its self-conscious blend of field and laboratory practices and its explicit integration with other areas of biology such as ecology, animal behavior, and evolution in order to study adaptation. Comparing the intersecting careers of Knut Schmidt-Nielsen and George Bartholomew highlights two strikingly different approaches to physiological ecology. These alternative approaches to studying the interactions of organisms and environments also differed in important ways from the organismal biology championed by leading figures in the modern synthesis.

Life under water: physiological adaptations to diving and living at sea

This review covers the field of diving physiology by following a chronological approach and focusing heavily on marine mammals. Because the study of modern diving physiology can be traced almost entirely to the work of Laurence Irving in the 1930s, this particular field of physiology is different than most in that it did not derive from multiple laboratories working at many locations or on different aspects of a similar problem. Because most of the physiology principles still used today were first formulated by Irving, it is important to the study of this field that the sequence of thought is examined as a progression of theory. The review covers the field in roughly decadal blocks and traces ideas as they were first suggested, tested, modified and in some cases, abandoned. Because diving physiology has also been extremely dependent on new technologies used in the development of diving recorders, a chronological approach fits well with advances in electronics and mechanical innovation. There are many species that dive underwater as part of their natural behavior, but it is mainly the marine mammals (seals, sea lions, and whales) that demonstrate both long duration and dives to great depth. There have been many studies on other diving species including birds, snakes, small aquatic mammals, and humans. This work examines these other diving species as appropriate and a listing of reviews and relevant literature on these groups is included at the end.