Gregory Retallack

Gregory Retallack
Greg Retallack, near Suplee, central Oregon, 1982
Born (1951-11-08) 8 November 1951 (age 75)
Hobart, Tasmania
CitizenshipAmerican and Australian
EducationMacquarie University,
University of New England (Australia)
Known forPaleopedology
SpouseDiane Retallack
Scientific career
Thesis A biostratigraphy for terrestrial Triassic rocks of Gondwanaland  (1978)
Rodney E. Gould
Websitehttps://blogs.uoregon.edu/gregr/

Gregory John Retallack (born 8 November 1951) is an Australian paleontologist, geologist, and author who specializes in paleopedology, the study of fossil soils. He is a professor emeritus at University of Oregon and his research is primarily concerned with the fossil record of soils though Earth history. His research has included investigations into climate change, the extinction of dinosaurs, and the origins of upright walking humans. Retallack has controversially claimed that Ediacaran-era fossils represent terrestrial lichens as opposed to the consensus view that they present marine organisms including animals. He has written two books on paleopedology, and has appeared in numerous media shows.

Biography

Retallack was born 8 November 1951 in Hobart, Australia. He attended school in Hurstville, and Epping, as well as The King's School, Parramatta. He studied biology and paleontology at Macquarie University where he received a B.A in 1973. He received a BSc Hons with University Medal in 1974 from the University of New England (Australia); and a PhD in 1978 in geology from the same university. After a postdoctoral fellowship at Indiana University Bloomington he joined the faculty at the University of Oregon in 1981. He was a professor in the Department of Geological Sciences since 1992, and Director of the Condon Collection of the University of Oregon Museum of Natural and Cultural History since 2009.

Retallack on Mount Cook, New Zealand, 1974

A fossil collector since a young age, Retallack was outspoken concerning federal seizure in 1993 of Sue (dinosaur) the skeleton of Tyrannosaurus rex excavated by Pete Larson.

Work

Evolution of life on land

Oligocene fossil soils of well-drained woodlands (red bands) and swamps (black spots) in the Painted Hills, Oregon

Retallack's research focuses on the study of paleosols (fossilized soils) to reconstruct ancient environments. In 1973, he proposed that paleosols preserved beneath fossil plant horizons could provide data on ancient plant communities that plant fossils alone could not reveal. He has applied this approach to various stages of evolutionary history, offering hypotheses that sometimes challenge established scientific understanding.

Research findings

Retallack has used paleosols to investigate several major extinction and evolutionary events. Regarding climate change, he argued that the coevolution of grasslands and grazers over the past 50 million years drove global cooling via carbon biosequestration. In the field of human evolution, Retallack's fieldwork in Kenya concerning Proconsulidae (primates ancestral to humans) led him to suggest that the evolutionary transition to an upright stance occurred in woodland environments rather than in open savannas. Regulation of global temperature by the balance of plants and animals has been called the Proserpina Principle.

He has also applied this methodology to mass extinction events. Studying the Cretaceous-Paleogene boundary in Montana, he hypothesized that acid rain resulting from an extraterrestrial impact contributed to the extinction of dinosaurs. Similarly, his work in Antarctica on the Permian-Triassic boundary led to the hypothesis that the mass extinction was driven by a greenhouse gas crisis caused by methane released from coal intrusions during massive volcanic events (flood basalts). Furthermore, he has proposed a "woodland hypothesis" regarding the Devonian transition of vertebrates from fish to amphibians.

In 2013, Retallack identified supposed fossils in Paleoproterozoic paleosols from South Africa, which he named Diskagma. He identified the species as a fungus comparable to the living Geosiphon. Dated to 2.2 billion years old, these fossils would push back the record of life on land significantly from the previously accepted record of 1.2 billion years

Retallack's work interpreting the Avalon and White Sea assemblages of the Ediacaran biota as lichens has been challenged. His proposal that Ediacaran fossils were preserved in subaerial paleosols, and thus not marine fossils, has been supported by a minority of researchers but not other paleontologists. Nature called it a "controversial claim" in a news report, in which paleontologist Guy Narbonne said "[I]t quickly became clear that there are simpler explanations for the features Retallack had validly noted, and most of us moved on to more promising explanations." Despite a majority of Ediacaran researchers who reject his claims based on a body of research, Retallack continues to test his position.

In 2020, Retallack and other researchers claimed to have found Dickinsonia fossils from Bhimbetka rock shelters, India. However, in 2023 other researchers found that the material was actually the decayed remnants of a beehive.

Media appearances

Retallack's work has been featured in several documentaries and science programs. His research on the Late Permian extinction appeared in the BBC's The Day the Earth Nearly Died and the Science Channel's Miracle Planet. Additionally, an episode of Prehistoric Predators on the National Geographic Channel covered his work on the Miocene of Panama. His findings regarding early life on land were also discussed on radio programs broadcast by National Public Radio, the Canadian Broadcast Corporation, and Oregon Public Broadcasting.

Paleosols (massive red bands) at horizons for Ediacaran fossils in Brachina Gorge, South Australia.

Boards

Retallack has served as an associate or technical editor for such scientific journals as Geology, PALAIOS, and Journal of Sedimentary Research. His fellowships include the Geological Society of America, and the American Association for the Advancement of Science.

He served as the president and vice president of the Cordilleran Section of the Paleontological Society, of the Oregon Academy of Sciences, and of the University of Oregon Chapter of the Society of Sigma Xi.

Awards and honors

Retallack has been honored for his research, including the Stillwell Award of the Geological Society of Australia, for best paper in the society journal in 1977, Ingerson Award of the Geochemical Society in 2015, and the Antarctica Service Medal of the U.S. National Science Foundation in 1999. He has been an invited lecturer throughout the U.S., and also to Germany, England, China, Thailand and India.

Bibliography

Books

Selected publications

References

  1. ↑ Retallack, G. J. (2019). Soils of the past: an introduction to paleopedology (3rd ed.). Chichester, United Kingdom: Wiley. ISBN 978-1-119-53040-4.
  2. 1 2 Jones, N. (February 2013). "Soil or sea for ancient fossils". Nature Geoscience. 6 (2): 84. Bibcode:2013NatGe...6...84J. doi:10.1038/ngeo1713.
  3. 1 2 3 4 5 Retallack, Gregory (2021). "Curriculum Vitae" (PDF). University of Oregon. Retrieved 20 May 2026.
  4. ↑ Retallack, Greg J. (1993). "Fossils are for everyone". Newsweek. 121: 8. Archived from the original on 6 April 2025.
  5. ↑ Retallack, G. J.; Bestland, E. A.; Fremd, T. J. (2000). Eocene and Oligocene paleosols and environmental change in central Oregon. Boulder, Colorado: Geological Society of America Special Paper 344. ISBN 978-0-8137-2344-0.
  6. ↑ Retallack, G. J. (1973). "Stratigraphy, palaeobotany and environmental analysis of an area around Pittwater, north of Sydney, N.S.W.". BSC Honours Thesis, University of New England. Armidale, New South Wales.
  7. ↑ Retallack, G. J. (1977). "Triassic palaeosols in the upper Narrabeen Group of New South Wales. Part II: Classification and reconstruction". Journal of the Geological Society of Australia. 24 (1–2): 19–35. doi:10.1080/00167617708728964.
  8. ↑ Retallack, G. J. (1997). "Palaeosols in the upper Narrabeen Group of New South Wales as evidence of Early Triassic palaeoenvironments without exact modern analogues". Australian Journal of Earth Sciences. 44 (2): 185–201. Bibcode:1997AuJES..44..185R. doi:10.1080/08120099708728303.
  9. ↑ Retallack, G. J. (2013). "Global cooling by grasslands in the geological past and near future". Annual Review of Earth and Planetary Sciences. 41: 5.1–18. doi:10.1146/annurev-earth-050212-124001.
  10. ↑ Driese, Steven G. (2021). "Soils, Chemical Weathering, and Climate Change in Earth History". In Hunt, Allen (ed.). Hydrogeology, Chemical Weathering, and Soil Formation. Advancing Earth and Space Sciences.
  11. ↑ Retallack, G. J. (2007). "Paleosols". In Henke, W.; Tattersall, I. (eds.). Handbook of paleoanthropology, Volume 1. Principles, methods and approaches. Vol. 1. Berlin: Springer Verlag. pp. 383–408.
  12. ↑ Retallack, G. J. (2004). "End-Cretaceous acid rain as a selective extinction mechanism between birds and dinosaurs". In Currie, P. J.; Koppelhus, E. B.; Shugar, M. A.; Wright, J. L. (eds.). Feathered dragons: studies on the transition from dinosaurs to birds. pp. 35–64.
  13. ↑ Retallack, G. J.; Jahren, A. H. (2008). "Methane release from igneous intrusion of coal during Late Permian extinction events". Journal of Geology. 116 (1): 1–20. Bibcode:2008JG....116....1R. doi:10.1086/524120. S2CID 46914712.
  14. ↑ Retallack, G. J. (2011). "Woodland hypothesis for Devonian evolution of tetrapods". Journal of Geology. 119 (3): 235–358. Bibcode:2011JG....119..235R. doi:10.1086/659144. S2CID 128827936.
  15. 1 2 Retallack, G. J.; Krull, E. S.; Thackray, G. D.; Parkinson, D. (2013). "Problematic urn-shaped fossils from a Paleoproterozoic (2.2 Ga) paleosol in South Africa". Precambrian Research. 235: 71–87. Bibcode:2013PreR..235...71R. doi:10.1016/j.precamres.2013.05.015.
  16. ↑ Peter Byrne (24 April 2014). "Early Life in Death Valley". Quanta Magazine. Retrieved 8 May 2014. Reprinted in ScientificAmerican.com
  17. ↑ Retallack, G. J. (1994). "Were Ediacaran fossils lichens?". Paleobiology. 20 (4): 523–544. Bibcode:1994Pbio...20..523R. doi:10.1017/S0094837300012975. S2CID 129180481.
  18. ↑ Waggoner, B. (1995). "Comment on "Were Ediacaran fossils lichens?"". Paleobiology. 21 (3): 397–398. Bibcode:1995Pbio...21..393W. doi:10.1017/S0094837300013373. S2CID 82550765.
  19. 1 2 3 Retallack, G. J. (2013). "Ediacaran life on land". Nature. 493 (7430): 89–92. Bibcode:2013Natur.493...89R. doi:10.1038/nature11777. PMID 23235827. S2CID 205232092.
  20. 1 2 Xiao, Shuhai; Knauth, L. Paul (3 January 2013). "Fossils come in to land: Muddying the waters / Not All At Sea" (PDF). Forum. Nature. 493 (7430): 28–29. doi:10.1038/nature11765.
  21. ↑ Waggoner, B. M. (1995). "Ediacaran Lichens: A Critique". Paleobiology. 21 (3): 393–397. Bibcode:1995Pbio...21..393W. doi:10.1017/S0094837300013373. ISSN 0094-8373. JSTOR 2401174. S2CID 82550765.
  22. ↑ Waggoner, B. M.; Collins, A. G. (2004). "Reductio Ad Absurdum: Testing The Evolutionary Relationships Of Ediacaran And Paleozoic Problematic Fossils Using Molecular Divergence Dates". Journal of Paleontology. 78 (1): 51–61. Bibcode:2004JPal...78...51W. doi:10.1666/0022-3360(2004)078<0051:RAATTE>2.0.CO;2. S2CID 8556856.
  23. ↑ Switek, Brian (12 December 2012). "Controversial claim puts life on land 65 million years early". Nature. doi:10.1038/nature.2012.12017. S2CID 130305901. Retrieved 19 November 2013.
  24. ↑ Weyland, W. C.; Droser, M. L. (17 November 2025). "Reply to comment by Retallack (2025) on ' The Ediacaran aquarium: insights from the Nilpena Ediacara National Park 1T-F marine ecosystem (Ediacara member, Rawnsley Quartzite) '". Australian Journal of Earth Sciences. 72 (8): 1161–1163. doi:10.1080/08120099.2025.2590158. ISSN 0812-0099.
  25. ↑ Bobrovskiy, Ilya; Hope, Janet M.; Ivantsov, Andrey; Nettersheim, Benjamin J.; Hallmann, Christian; Brocks, Jochen J. (21 September 2018). "Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals". Science. 361 (6408): 1246–1249. doi:10.1126/science.aat7228. hdl:1885/230014.
  26. ↑ Ivantsov, A. Yu.; Zakrevskaya, M. A. (1 December 2021). "Symmetry of Vendobionta (Late Precambrian Metazoa)". Paleontological Journal. 55 (7): 717–726. doi:10.1134/S0031030121070054. ISSN 1555-6174.
  27. ↑ Antcliffe, Jonathan B.; Hancy, Anthony D. (2013). "Reply to Retallack (2013): Ediacaran characters". Evolution & Development. 15 (6): 389–392. doi:10.1111/ede.12048. ISSN 1525-142X.
  28. ↑ Callow, Richard H. T.; Brasier, Martin D.; Mcilroy, Duncan (2013). "Discussion: "Were the Ediacaran siliciclastics of South Australia coastal or deep marine?" by Retallack et al., Sedimentology, 59, 1208–1236". Sedimentology. 60 (2): 624–627. doi:10.1111/j.1365-3091.2012.01363.x. ISSN 1365-3091.
  29. ↑ Retallack, G. J. (17 November 2025). "Comment on ' The Ediacaran aquarium: insights from the Nilpena Ediacara National Park 1T-F marine ecosystem (Ediacara member, Rawnsley Quartzite) ' by Weyland and Droser (2025)". Australian Journal of Earth Sciences. 72 (8): 1159–1160. doi:10.1080/08120099.2025.2590157. ISSN 0812-0099.
  30. ↑ Retallack, Gregory J.; Matthews, Neffra A.; Master, Sharad; Khangar, Ranjit G.; Khan, Merajuddin (1 February 2021). "Dickinsonia discovered in India and late Ediacaran biogeography". Gondwana Research. 90: 165–170. Bibcode:2021GondR..90..165R. doi:10.1016/j.gr.2020.11.008. ISSN 1342-937X. S2CID 229451488.
  31. ↑ Meert, Joseph G.; Pandit, Manoj K.; Kwafo, Samuel; Singha, Ananya (1 May 2023). "Stinging News: 'Dickinsonia' discovered in the Upper Vindhyan of India not worth the buzz". Gondwana Research. 117: 1–7. Bibcode:2023GondR.117....1M. doi:10.1016/j.gr.2023.01.003. ISSN 1342-937X. S2CID 255846878.
  32. ↑ "The day the Earth nearly died". Youtube. 12 March 2009. Retrieved 21 August 2013.
  33. ↑ "Death and rebirth". Youtube. 9 June 2009. Retrieved 21 August 2013.
  34. ↑ Retallack, G. J.; Kirby, M. X. (2007). "Middle Miocene global change and paleogeography of Panama". PALAIOS. 22 (6): 667–679. Bibcode:2007Palai..22..667R. doi:10.2110/palo.2006.p06-130r. S2CID 56409337.
  35. ↑ "Terror raptor". Youtube. Retrieved 21 August 2013.
  36. ↑ "Land creatures may not have come from the sea". National Public Radio. Retrieved 21 August 2013.
  37. ↑ "Fossils could preserv oldest land life". Canadian Broadcast Corporation. Retrieved 21 August 2013.
  38. ↑ "Evidence of the oldest life on land". Oregon Public Broadcasting. Retrieved 21 August 2013.