Ian McDougall (geologist)

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Ian McDougall (born May 24, 1935 in Hobart , Tasmania ; † November 10, 2018 ) was an Australian geologist and since 2001 professor emeritus at the Australian National University . As an internationally recognized geochronologist and expert in potassium-argon dating , he succeeded in radiometric dating of various rock layers in the Turkana basin in Kenya from the late 1970s . Based on this data, the exact age of fossils has since been determined, including important hominine finds such as Omo 1 and Omo 2 and the Nariokotome boy as well as fossilized bones of Australopithecus anamensis , Homo rudolfensis and Homo habilis .

Education and research in Hawaii

After attending the Friends' School run by Quakers in his hometown of Hobart, Ian McDougall studied geology and chemistry at the University of Tasmania from 1953 . For his bachelor's degree, he was mapping the Bridgewater area north of Hobart . In 1957 he moved to the Institute for Geophysics at the Australian National University, where he worked in the working group of geologist Germaine Joplin until 1961 for his doctoral thesis.

In 1960 McDougall married Pam Hodgson; the couple had three children.

With a CSIRO - Scholarship McDougall then went to the University of California, Berkeley , where he joined the laboratory of Garniss Curtis of the K-Ar dating einarbeitete in the then brand new method. At the same time he became a research assistant from 1961 and later a professor at the Australian National University. There he was u. a. involved in setting up a laboratory for radiometric dating and initially used this laboratory primarily for the now, for the first time, technically possible dating of relatively young, differently old volcanic rocks from several islands in Hawaii . The results of these measurements gave indications of the shift in volcanic activity in the area of ​​this chain of islands , which is consistent with other measurements on the theory of continental drift .

Research in the Turkana Basin

From 1978 onwards, Ian McDougall was entrusted with the dating of a lead horizon in the area of Omo and Lake Turkana in Kenya , a volcanic layer known as KBS tuff (Kay Behrensmeyer Site Tuff ) . Numerous hominine fossils had been discovered within and above this layer, which was detectable throughout the region, including the so-called Black Skull of Paranthropus aethiopicus . Below the layer was the type specimen - the skull KNM-ER 1470 - of Homo rudolfensis , which was discovered in 1972 under the direction of Richard Leakey at Koobi Fora and, due to its characteristics, was placed among the earliest specimens of the genus Homo . However, the age of the KBS tuff and thus the age of Homo rudolfensis in particular was controversial : the calculations were partly 1.6 million years, partly 2.6 million years.

In his non-fiction book Bones of Contention. Controversies in the Search for Human Origins , Roger Lewin has devoted several chapters to the dispute over the dating of the KBS tuff. According to this, the British geologists FJ Fitch and JA Miller had assigned the tuff layer an age of 2.61 million years at the end of the 1960s. There were early doubts about this dating, as reference fossils from other, similarly old African sites in the area of ​​the KBS tuff were missing and the local fossils - in particular pig teeth from the genus Mesochoerus - suggested an age of no more than 2.0 million years. The original features of the skull KNM-ER 1470 and the slow rate of evolution of the genus Homo assumed by Richard Leakey, however, spoke for the plausibility of dating to a significantly older epoch. At this, according to Lewin to what was then the world of paleoanthropologists appropriate assessment, a lecture by changed in February 1975 Garniss Curtis anything he during a meeting of the Geological Society of London held and in which he tuff layer an age of 1, 82 Attributed ± 0.04 million years ago; Curtis was alleged to have analyzed rock samples from another layer.

Both Curtis' laboratory at the University of California, Berkeley and Fitch and Miller in Great Britain insisted on the accuracy of their measurements in the following years, so that Richard Leakey and Glynn Isaac finally in 1978 a "neutral" expert who had not been involved in the dating dispute asked for his expertise: Ian McDougall. Its tuff dating using the potassium-argon method - 1.89 ± 0.01 million years - was published in Nature in 1980 , in the same issue as a second, independent fissure trace dating that is 1.87 ± 0.04 Had revealed millions of years. Since then, the dating of the tuff layer is considered certain.

In the years that followed, Ian McDougall dated numerous other layers in the Turkana Basin.

Publications (selection)

  • Determination of the Age of a Basic Igneous Intrusion by the Potassium-Argon Method. In: Nature. Volume 190, 1961, pp. 1184-1186, doi: 10.1038 / 1901184a0
  • with Robert A. Duncan: Migration of volcanism with time in the Marquesas Islands, French Polynesia. In: Earth and Planetary Science Letters. Volume 21, No. 4, 1974, pp. 414-420, doi: 10.1016 / 0012-821X (74) 90181-2
  • with Ronald T. Watkins: Age of hominoid-bearing sequence at Buluk, northern Kenya. In: Nature. Volume 318, 1985, pp. 175-178, doi: 10.1038 / 318175a0
  • with Meave Leakey , Craig S. Feibel, and Alan Walker : New four-million-year old hominid species from Kanapoi and Allia bay, Kenya. In: Nature. Volume 376, 1995, pp. 565–571, doi: 10.1038 / 376565a0 , full text (PDF)
  • with T. Mark Harrison: Geochronology and Thermochronology by the 40 Ar- 39 Ar Method. Oxford University Press, 2nd ed. 1999, ISBN 978-0195109207
  • with Meave Leakey and others: New hominin genus from eastern Africa shows diverse middle Pliocene lineages. In: Nature. Volume 410, 2001, pp. 433-440, doi: 10.1038 / 35068500
  • with Francis H. Brown and John G. Fleagle : Stratigraphic placement and age of modern humans from Kibish, Ethiopia. In: Nature. Volume 433, 2005, pp. 733–736, doi: 10.1038 / nature03258 , full text (PDF)
  • with Francis H. Brown and Bereket Haileab: Sequence of tuffs between the KBS Tuff and the Chari Tuff in the Turkana Basin, Kenya and Ethiopia. In: Journal of the Geological Society. Volume 163, 2006, pp. 185-204, doi: 10.1144 / 0016-764904-165
  • Brief history of isotope geology at the Australian National University. In: Australian Journal of Earth Sciences. Volume 55, No. 6-7, 2008, pp. 727-736, doi: 10.1080 / 08120090802155258
  • with Francis H. Brown: Geochronology of the pre-KBS Tuff sequence, Omo Group, Turkana Basin. In: Journal of the Geological Society. Volume 165, 2008, pp. 549-562, doi: 10.1144 / 0016-76492006-170
  • with Francis H. Brown and John G. Fleagle: Sapropels and the age of hominins Omo I and II, Kibish, Ethiopia. In: Journal of Human Evolution . Volume 55, No. 3, 2008, pp. 409-420, doi: 10.1016 / j.jhevol.2008.05.012
  • Age of volcanism and its migration in the Samoa Islands. In: Geological Magazine. Volume 147, No. 5, 2010, pp. 705-717, doi: 10.1017 / S0016756810000038
  • Perspectives on 40 ar- 39 ar dating. In: Geological Society, London, Special Publications. No. 378, pp. 9-20, 2013, doi: 10.1144 / SP378.20

Web links

Individual evidence

  1. ↑ Fellows update — November 2018. Australian Academy of Science, November 28, 2018, accessed January 6, 2019 .
  2. ↑ Entry McDougall, Ian in the Encyclopedia of Australian Science , accessed May 23, 2018
  3. ^ Roger Lewin: Bones of Contention. Controversies in the Search for Human Origins. Touchstone 1988, ISBN 0-671-66837-4
  4. ^ FJ Fitch and JA Miller: New Hominid Remains and Early Artefacts from Northern Kenya: Radioisotopic Age Determinations of Lake Rudolf Artefact Site. In: Nature . Volume 226, 1970, pp. 226-228, doi: 10.1038 / 226226a0
  5. ^ GH Curtis et al .: Age of KBS Tuff in Koobi Fora Formation, East Rudolf, Kenya. In: Nature. Volume 258, 1975, pp. 395-398, doi: 10.1038 / 258395a0
  6. ↑ Ian McDougall et al .: K – Age estimate for the KBS Tuff, East Turkana, Kenya. In: Nature. Volume 284, 1980, pp. 230-234, doi: 10.1038 / 284230a0
  7. ^ AJW Gleadow: Fission track age of the KBS Tuff and associated hominid remains in northern Kenya. In: Nature. Volume 284, 1980, pp. 225-230, doi: 10.1038 / 284225a0
personal data
SURNAME McDougall, Ian
BRIEF DESCRIPTION Australian geologist
DATE OF BIRTH May 24, 1935
PLACE OF BIRTH Hobart , Tasmania, Australia
DATE OF DEATH November 10, 2018