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No. 81: May-Jun 1992

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Plants Of The Apes

Many biologists are convinced that apes, bears, cats, and dogs eat plants -- many of them obviously distasteful -- in order to medicate themselves for diseases and parasites. What also seems likely, according to K. Strier, of the University of Wisconsin, Madison, is that some monkeys regulate their fertility by the judicious consumption of certain plants. Going even farther, K. Glander, Duke University, suggests that howler monkeys control the sex of their offspring through their diets.

Glander divides howler monkey females into three groups. In the first are the high-ranking females that predominantly produce male offspring. This 'male-offspring' strategy favors these females because the males they produce tend to become dominant adults that will pass on more of the females' genes than would female offspring, who are limited in the number of infants they can engender in comparison to the males. Similar optimization strategies, according to Glander, induce middleranking females to produce mainly female progeny, and low-ranking females to birth almost all males.

These howler monkeys seem to control the sex of their offspring pharmologically by selecting certain plants to eat. These plants, in turn, control the electrical conditions in the females' reproductive tracts to either attract or repel sperm carrying the male Y-chromosomes, which are thought to carry different electrical charges than the X-carrying sperm! (Lewin, Roger; "What Monkeys Chew to Choose Their Children's Sex," New Scientist, p. 15, February 22, 1992. Also: Gibbons, Ann; "Plants of the Apes," Science, 255:921, 1992.)

Comments. It will take much more research to validate these startling assertions. We also have to ask how these instincts (or conscious, calculated strategies?) evolved. Since so many of the medicinal plants are distasteful, why would the monkeys eat them in the first place and thus learn, instinctively or consciously, their value in advancing the prospects for their genes?

Reference. The medicinal use of plants by mammals (more common than generally supposed) is cataloged in BMB21 in our catalog: Biological Anomalies: Mammals I. Ordering information here.

From Science Frontiers #81, MAY-JUN 1992. 1992-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987