John Damuth

John Damuth's CV


January 21, 2024. New book in press! John Damuth and Lev Ginzburg, Nonadaptive Selection: An evolutionary source of ecological laws.

The book forges a wide variety of topics into an innovative, simple — yet profound, argument about selection processes at higher levels of organization than the individual, and how these might form the basis for genuine biological laws. It will be out in 2024 from the University of Chicago Press.

Research Details

Preparing the ground

My primary training has been in vertebrate paleontology and related fields, but my graduate work and subsequent research experience also included a broad knowledge of evolutionary biology and ecology in general. (My PhD degree is in "Evolutionary Biology".) Methods to reconstruct the ecologies of fossil species and faunas have remained my ultimate goal, but this requires familiarity with organismic biology and ecology in its own right. However, study of evolution and ecology of the contemporary world is practiced and motivated by questions that do not always translate well into a deep historical context. My approach has been to seek out and investigate general processes and mechanisms in ecology and evolution that can be used to make reliable inferences about the remote past, but are based on demonstrable regularities in the present day. In this process I have been led far afield into ecology and evolution, and, ironically, my published work may reflect this as much or more than it does paleobiological applications.

Body-size allometry of population density and population energy-use

In 1981 I carried out a comprehensive literature survey of the size-scaling of animal population densities, starting with herbivorous mammals and later including a wide range of terrestrial and aquatic species. Of course, population density (individuals per km2) decreases with increasing body mass. My work showed, though, that the rate of this decrease tends to be the value one would expect if population trophic energy-use of each species is independent of its body size. That is, no species has an advantage in obtaining trophic energy based on its body size alone. This “energetic equivalence” pattern is widespread, particularly when several orders of magnitude in body size are represented in a trophic level.

Application to fossil mammal localities

Fossil assemblages sample a community of living species, but the resulting relative abundances of different-sized species that are recovered by paleontologists are subject to several major biases. I used the energy equivalence relationship to try to quantify the overall effect of such biases in a number of fossil collections. Do the relative numbers of individuals of different species recovered from a fossil locality retain quantitative ecological information? The answer is yes — but not in all circumstances, and the relative abundances can never be taken at face value. However, we usually have a good idea of how to ameliorate the remaining biases.

Multilevel Selection and Contextual Analysis

The mid 1980’s were a time of intellectual turmoil in the study of levels of selection — both at the organismic/group and species/clade levels. Lorraine Heisler and I developed a theoretical approach to multilevel selection that has become a standard for modeling and data analysis in this research area. We introduced a statistical technique called contextual analysis that is particularly well suited for investigating the evolution of individual organisms in populations with group structure, e.g., the “group selection” of altruistic behaviors). Using our approach to multilevel selection clarifies a number of issues — such as the relationship between selection at organismic versus species levels, the meaning of “emergence,” and the meaning of “adaptation” among species.

Size-scaling of Metabolism, Geometry of Transport Networks

Starting in 1932, Kleiber popularized the empirical observation that metabolic rate tends to scale as body mass raised to the 3/4 power, but he had no explanation of this observation. Serious causal modeling supporting the Kleiber observation, involving constraints on the internal transport networks of metabolites, began only with the West-Brown-Enquist (WBE) group in 1997. This was quickly followed in 1999 by an apparently competing model proposed by Banavar, Maritan and Rinaldo (the BMR group), with whom I have been working for many years. The early models were complex, and subtly internally inconsistent. Another decade of work resulted in our joint presentation of a fully consistent model that largely reconciles the WBE and BMR models, supports a 3/4 exponent as the most efficient, and both simplifies and generalizes the transport network approach. (Banavar, et al., 2010).

A wide range of topics involving mammal ecology and paleoecology

This includes reconstruction of paleodiets, tooth wear in living and fossil species, and the role of ingested soil on tooth wear rates; Estimation of body mass of fossil species; Reconstruction of paleoclimates and Miocene faunal change in relation to climate change and CO2; Life history allometry; Body mass on islands; Relational database design and implementation, and the concept of databases as virtual museums; Craniodental adaptations of marsupials, and Australian paleoecology.

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