G. Edgar Folk Jr.
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G. Edgar Folk, Jr.

G. Edgar Folk, Professor Emeritus of Molecular Physiology at the University of Iowa, is interviewed in July 2007 in this segment of “Living History of Physiology” by Charles Wunder, also a Professor Emeritus at the University of Iowa. Dr. Folk’s career has focused largely on hibernation and circadian rhythm/biological clocks. He was one of the founders of the fact that indeed, bears do hibernate during the cold months.

Dr. Folk had a very early influence on his interest in science – his family. His family would walk in the woods behind his house and his father would pose inquisitive questions to him and his two siblings about various things, such as reasoning why one songbird lays one egg per season and another lays four eggs per season. Dr. Folk’s father also had an interest in producing new kinds of gladioli and began cross pollinating. Scientific experiments were a regular part of dinner conversation.

Dr. Folk attended Harvard University for both undergraduate and graduate education. During his undergraduate years, he befriended a family of skiing, and he and the family skied often on the top of Mt. Washington. Later in his career, he was known as an expert on cold weather physiology, and his first experience was gained by walking through deep snow before and after skiing to the hut in which they camped. Another important influence person was Donald Griffin who Dr. Folk said interested him in the physiology of hibernation. With Dr. Griffin, Dr. Folk banded 16,000 hibernating bats to help Dr. Griffin write papers about migration, but another important finding was that some of the bats lived long enough to give them records of 30 and 35 years, which was unheard of in small creatures. Dr. Griffin was the individual to discover the ability of echolocation in bats. 

Under the encouragement of “Jack” Welch at Harvard, Dr. Folk fulfilled his coursework for a Ph.D., writing two papers on hibernation. He said these were papers that influenced the rest of his life because he realized he enjoyed assembling data together and then writing technical papers about it. Dr. Welch also arranged for a fellowship to send Dr. Folk to Cuba and Haiti to train in biology. In Cuba, at the Atkins Institute in the middle of the rain forest, he designed an experiment to study the effect of latitude and climate on the reproduction of tropical bats.

After graduate school, he joined the National Guard and became a sergeant in the medical core, followed by a very brief stint in the Merchant Marine, as he soon received a call to head the Harvard Fatigue Lab that was under the control of the Army. He was asked to run an environmental chamber at -50 degrees to work with soldiers in exercise physiology. He worked in the laboratory for four years, finishing his thesis and receiving his Ph.D. in 1947 in the meantime. The laboratory, however, was closed in 1947, shortly after his degree was awarded. After the Harvard Fatigue Lab, he worked at Bowdoin College in Maine for about six years, helping with the Bowdoin-Kent Island Biological Station. Here he did research on hibernation in the birds of the island. In 1953, he left Bowdoin to accept a teaching position in the physiological department at the University of Iowa. Here he wrote the first textbook on environmental physiology, and two years later there were eight books with the same title.

Dr. Folk is well-known for his work on Circadian rhythm and the biological clock. Circadian rhythms are under control of the sunrise and sunset. They are able to be manipulated, and researchers are able to give an animal a four-hour light period, a 12-hour light period, or even continuous light. The biological clocks in animals respond differently to different light periods. He did some work in a lab in the summertime far enough north that there were 82 days of sun, just traveling in a circle, overhead. He studied the effect of this photo period on animals and Eskimos, which he said prepares an animal for hibernation.

As for his research on hibernation, at many meetings Dr. Folk attended, a frequent topic of conversation was, “do bears hibernate?” Everyone agreed that until there was an implantable physiological radio for use in difficult animals, they would never know. A colleague of his, Warren Essler, devised the Iowa Transmitter to implant into the body cavity of difficult animals. By having it in these animals, Dr. Folk was able to study whether bears hibernated or not. The transmitter reported the EKG, heart rate, and body temperature of three kinds of bears: black, grizzly and polar. His studies showed that all three species of bears do not eat, drink, urinate or defecate for up to seven months.

In his study of biological clocks, it was always widely considered that the clock within the body and all the organs were regulated by two organs in the brain. He said he hypothesized, because of Circadian rhythm, that maybe these organs regulated themselves, so he started a program of isolating organs to see if they had their own clocks. His research showed they all had their own “clocks” and were able to regulate themselves, recommending that brain control be called a synchronizer and not a regulator.


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