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No. 100: Jul-Aug 1995

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When Humans Were An Endangered Species

At one point during the last 400,000 years, the human population worldwide was reduced to only about 10,000 breeding men and women -- the size of a very small town. What caused this population "bottleneck"? Did a population crash engulf the entire globe. If not, who was spared?

Such questions arise from a surprising observation: Human DNA is remarkably uniform everywhere humans are found. This hidden genetic uniformity is difficult to believe if one strolls through a cosmopolitan city like New York or Paris. Nevertheless, compared to the DNA of the great apes, whose mutation rates should be close to ours, human genes on the average show far fewer mutations. Human DNA from Tokyo and London is more alike than that from two lowland gorillas occupying the same forest in West Africa. Harvard anthropologist M. Ruvolo has commented: "It is a mystery that none of us can explain."

The clear implication is that humans recently squeezed through a population bottleneck, during which many accumulated mutations were wiped out. In a sense, the human race began anew during the last 400,000 years. Unfortunately, DNA analysis cannot say where the very grim reaper came from.

(Gibbons, Ann; "The Mystery of Humanity's Missing Mutations," Science, 267:35, 1995.)

Comment. The hand that wiped the slate clean, or nearly so, might have been a meteor impact, a pandemic, the Ice Ages, a flood, volcanism, etc. Whatever it was, it seems to have largely spared Africa. The chimps and gorillas there apparently did not pass through the bottleneck. Even more interesting is the observation that the DNA of Subsaharan Africans does shows more variability and therefore seems older than that from humans elsewhere on the planet. (See BMG9 in our catalog volume: Biological Anomalies: Humans III.) Or perhaps Subsaharan DNA only seems older because it was not forced through that bottleneck. There are implications here for the African Eve theory.

From Science Frontiers #100, JUL-AUG 1995. 1995-2000 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