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Heads of Laboratories

Head shot of Joel Cohen
Joel E. Cohen, Ph.D., Dr.P.H.
Abby Rockefeller Mauzé Professor
Laboratory of Populations

Living populations have “ensemble properties,” such as birth rates, death rates, and growth rates, that are not characteristics of any individual. Dr. Cohen develops concepts helpful for understanding ensemble properties of populations, human and non-human, and tests these concepts in applications to human fertility, mortality, and migration; farms, fisheries, forests, and wildlife; infectious diseases; and food webs.

The human species is a node in a network of feeding relationships, known as a “food web,” with thousands of other species. Species that humans eat are conventionally studied as part of agriculture. Species that eat humans, which are mainly the agents or vectors of infectious diseases, are studied in epidemiology. Humans, the species humans eat, and the species that eat humans are nodes in a global food web, studied in ecology. The global food web includes many species not directly linked to humans by feeding and strongly interacts with the physical and chemical environment.

Dr. Cohen and his colleagues aim to describe, understand, and offer insights that can help manage the global food web for the well-being of humans and other species. They combine the perspectives of demography, agriculture, epidemiology, ecology, and environmental sciences. Their work uses concrete problems to motivate the development of new concepts for understanding populations and aims to crystallize these concepts into mathematical, statistical, and computational tools applicable to scientific and practical problems.

For example, Dr. Cohen and colleagues study Chagas disease (also called American trypanosomiasis), an insect-borne chronic infectious disease that infects children in Latin America and eventually kills many young adults in their prime years of work and family rearing. No vaccine is available to prevent infection. Because the affected people are poor, commercial incentives to develop a vaccine are weak. The drugs available for treatment are toxic. Dr. Cohen collaborates with Argentine colleagues who conduct field studies of Chagas disease to understand the ecology of disease transmission within and among households in poor rural villages in northwest Argentina. Based on data from these field studies, they develop mathematical models of the relations among humans; domestic animals like dogs, cats, chickens, and goats; the insects that transmit infection; and the trypanosome that causes disease. Their findings lead to specific recommendations of low-technology, low-cost interventions to prevent infection of people at risk.

Variability is a pervasive theme in studies of the Laboratory of Populations. For example, the counties of Norway each consist of multiple municipalities. The average and the variance (or scatter) of the number of people or population density of municipalities within a county vary from one county to another. But each county's variance of population density is approximately a power-law function of its average population density. This power-law relationship of variance to average across different sampling units — in this case counties — is known as Taylor’s law in ecology. It has other names in other fields of science where the same power-law relation of variance to mean occurs. Dr. Cohen and colleagues are studying Taylor’s law theoretically and empirically in bacteria, trees, fish, voles, humans, and other species, including those involved in Chagas disease, and are exploring its practical applications to sampling, projection, and management.


A.B. in applied mathematics, 1965
A.M. in applied mathematics, 1967
Ph.D. in applied mathematics, 1970
M.P.H., 1970
Dr.P.H., 1973 
Harvard University


Assistant Professor, 1971–1972
Associate Professor, 1972–1975
Harvard University

Professor, 1975–
The Rockefeller University

Professor, 1995–
Columbia University


MacArthur Fellow, 1981

Fred L. Soper Award, Pan American Health and Education Foundation, 1997

Tyler Prize, University of Southern California, 1999


National Academy of Sciences
American Academy of Arts and Sciences
American Philosophical Society
Fellow, American Association for the Advancement of Science


Cohen, J.E. and Xu, M. Random sampling of skewed distributions implies Taylor’s power law of fluctuation scaling. Proc. Natl. Acad. Sci. U.S.A. 112, 7749–7754 (2015).

Giometto, A. Sample and population exponents of generalized Taylor’s law. Proc. Natl. Acad. Sci. U.S.A. 112, 7755–7760 (2015).

Lagrue, C. et al. Parasitism alters three power laws of scaling in a metazoan community: Taylor’s law, density-mass allometry, and variance-mass allometry. Proc. Natl. Acad. Sci. U.S.A. 112, 1791–1796 (2015).

Gürtler, R.E. et al. Domestic animal hosts strongly influence human-feeding rates of the Chagas disease vector Triatoma infestans in Argentina. PLoS Negl Trop Dis 8, e2894 (2014).

Gürtler, R.E. et al. Key source habitats and potential dispersal of Triatoma infestans populations in northwestern Argentina: implications for vector control. PLoS Negl Trop Dis 8, e3238 (2014).

Dr. Cohen is a faculty member in the David Rockefeller Graduate Program and the Tri-Institutional M.D.-Ph.D. Program.