Gregory John Retallack (born 8 November 1951) is an Australian paleontologist, geologist, and author who specializes in the study of fossil soils (

paleopedology Paleopedology (palaeopedology in the United Kingdom) is the discipline that studies soils of past geological eras, from quite recent (Quaternary) to the earliest periods of the Earth's history. Paleopedology can be seen either as a branch of soil s ...

). His research has examined the fossil record of soils though major events in Earth history, extending back some 4.6 billion years. Among his publications he has written two standard

textbooks, said N. Jones in '' Nature Geoscience'' "Retallack has literally written the book on ancient soils."

Biography

Retallack moved with his family from Hobart, Tasmania at age 4. He grew up in Hurstville and then

Epping Epping may refer to: Places Australia * Epping, New South Wales, a suburb of Sydney ** Epping railway station, Sydney * Electoral district of Epping, the corresponding seat in the New South Wales Legislative Assembly * Epping Forest, Kearns, a he ...

, in the suburbs of Sydney. He attended The King's School, Parramatta, then studied biology and paleontology at

Macquarie University Macquarie University ( ) is a public research university based in Sydney, Australia, in the suburb of Macquarie Park. Founded in 1964 by the New South Wales Government, it was the third university to be established in the metropolitan area of S ...

. 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 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 The University of Oregon Museum of Natural and Cultural History (MNCH), commonly known as the UO Natural History Museum, is an American natural history museum at the University of Oregon in Eugene. Located near Hayward Field on the east side of ...

since 2009. Since retirement in 2022 he has been a professor emeritus. RetallackMtCook

A fossil collector since the age of 6, Retallack was outspoken concerning federal seizure in 1993 of

Sue (dinosaur) Sue is the nickname given to FMNH PR 2081, which is one of the largest, most extensive, and best preserved ''Tyrannosaurus rex'' specimens ever found, at over 90 percent recovered by bulk. It was discovered on August 12, 1990, by American explo ...

the skeleton of Tyrannosaurus rex excavated by

Pete Larson Peter Lars Larson (born 1952) is an American fossil expert and president of the Black Hills Institute of Geological Research. He led the team that excavated " Sue", one of the largest and most complete specimen of ''Tyrannosaurus rex'' found to ...

Work

Evolution of life on land

In 1973, Retallack discovered that paleosols were preserved among fossil roots below some kinds of fossil plant horizons and that paleosols could reveal aspects of plant communities difficult to infer from the fossil plants themselves. This novel approach to reconstructing life on land could be applied to understanding major events in evolution, sometimes supplementing and sometimes challenging prior understanding. Initial work was on Triassic vegetation and climate. Later construction of

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

paleoclimate Paleoclimatology (British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...

time series led to the idea that grassland-grazer coevolution was responsible for climatic cooling over the past 50 million years, which has implications for biosequestration of carbon. Fieldwork in Kenya on paleosols associated with apes (

Proconsulidae Proconsulidae is an early family of primates that lived during the Miocene epoch in Kenya, and was restricted to Africa. Members of the family have a mixture of Old World monkey and ape characteristics, so the placement in the ape superfamily Hom ...

) ancestral to humans revealed that the evolutionary transition to upright stance occurred in woodlands rather than savannas. Paleosols of the Cretaceous-Paleogene boundary in Montana implicated abrupt paleoclimatic change and acid rain from extraterrestrial impact in the extinction of dinosaurs Work on the Permian-Triassic boundary in Antarctica lead to formulation of an hypothesis of

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...

crisis due to methane outburst associated with flood basalt in this greatest of all mass extinctions

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

fossil soils at sites for tetrapods suggest a woodland hypothesis for the evolutionary transition from fish to

amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...

. Retallack discovered fossil soils at classical South Australian sites for the Ediacara biota and reported it is evidence that these fossils formerly regarded as marine were instead terrestrial organisms such as

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.slime molds and microbial colonies. Retallack has also reinterpreted volcanic tuffs of Newfoundland as terrestrial lapilli and sanidine tuffs, and so found fossiliferous Ediacaran paleosols there as well A Paleoproterozoic paleosol with problematic fossils (''

Diskagma ''Diskagma'' ("disc-like fragment") is a genus of problematic fossil from a Paleoproterozoic (2200 million years old) paleosol from South Africa, and significant as the oldest likely eukaryote and earliest evidence for megascopic life on land. ...

'') comparable with the living ''

Geosiphon ''Geosiphon'' is a genus of fungus in the family Geosiphonaceae. The genus is monotypic, containing the single species ''Geosiphon pyriformis'', first described by Kützing in 1849 as ''Botrydium pyriforme''. In 1915, Von Wettstein characterized ...

'' (a fungus) could suggest a long evolutionary history for life on land.

from South Africa is as old as 2.2 billion years, pushing back the arrival of life on land much further than the previous record of 1.2 billion years. Such putative ancient and complex life on land could support the view that life originated in soil. PaintedHillspaleosols

Retallack's work on Late Permian mass extinction was featured on several television documentaries, including the BBC's ''

The Day The Earth Nearly Died ''The Day The Earth Nearly Died'' is a British documentary produced by BBC to the science and philosophy series ''Horizon'' in 2002. The program focuses on the mystery of the Permian extinction, which scientists believe killed over 90% of all life ...

'' and Science Channel USA's ''

Miracle Planet ''Miracle Planet'' is a six-part documentary series, co-produced by Japan's NHK and the National Film Board of Canada (NFB), narrated by Christopher Plummer (Seiko Nakajo in the original Japanese), which tells the 4.6-billion-year-old story of ...

'' episode "Death and Rebirth". His work on Miocene of Panama was featured in National Geographic Channel USA's "Terror Raptor" episode of ''Prehistoric Predators''. Radio interviews concerning his recent work on early life on land were broadcast by Richard Harris for National Public Radio, Bob McDonald for Canadian Broadcast Corporation and Dave Miller for Oregon Public Broadcasting. In a challenge to young earth creationism, Retallack debunked interpretation of the fossil forests of Yellowstone National Park as deposits of volcanic lahars in which tree trunks landed upright, by showing that the fossil stumps were rooted in moderately developed paleosols. Because moderate development of soils can take as long as 5000 years, only a few paleosols in succession are needed to exceed the young earth creationism age of the Earth, and at Yellowstone there are at least 24 successive fossil forests. Sequences of paleosols is just one of many lines of physical evidence that young earth creationism does not explain as well as conventional geology.

Paleobotany

In addition to paleopedology, Retallack continues research in

paleobotany Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeogr ...

. His special interests include Triassic fossil plants such as ''

Pleuromeia ''Pleuromeia'' is an extinct genus of lycophytes. They are related to modern quillworts (''Isoetes''). ''Pleuromeia'' dominated vegetation during the Early Triassic all over Eurasia and elsewhere, in the aftermath of the collapse of floral comm ...

'', '' Isoetes'', ''

Dicroidium ''Dicroidium'' is an extinct genus of fork-leaved seed ferns that were widely distributed over Gondwana during the Triassic (). Their fossils are known from South Africa, the Arabian Peninsula, Australia, New Zealand, South America, Madagascar ...

'' and ''

Lepidopteris ''Lepidopteris'' ("scaly fern") is a form genus for leaves of Late Permian to Late Triassic Period Pteridospermatophyta, or seed ferns, which lived from around 260 to 200 million years ago in what is now Australia, Antarctica, India, South Amer ...

''. With David Dilcher he developed a coastal hypothesis for the dispersal and rise to dominance of angiosperms. Retallack also developed new techniques for using stomatal index of fossil '' Ginkgo'' leaves to obtain past atmospheric carbon dioxide. This work led Retallack to propose the concept of paleoenvironmental regulation by the Proserpina Principle: plants cool the planet, whereas animals warm it. Retallack's name is honored by several fossils including '' Cladophlebis retallackii'', fossil fern foliage, ''

Sapindopsis ''Sapindopsis'' ("''Sapindus''-like") is an extinct form genus for leaves of the Cretaceous Period, originally considered similar to soapberry. Associated reproductive structures now suggest it was more closely related to planes and sycamores of ...

retallackii'' early angiosperm leaves and ''

Hypisodus ''Hypisodus'' is an extinct genus belonging to the family Hypertragulidae, within the order Artiodactyla, endemic to North America during the Eocene through Oligocene, living 37.2–26.3 Ma, existing for approximately . ''Hypisodus'' were pri ...

retallacki'', a fossil mouse deer. BrachinaGorgepaleosols

Archeology

In a study of soils at 84 temples of

Classical Greece Classical Greece was a period of around 200 years (the 5th and 4th centuries BC) in Ancient Greece,The "Classical Age" is "the modern designation of the period from about 500 B.C. to the death of Alexander the Great in 323 B.C." ( Thomas R. Marti ...

, Retallack discovered that each deity and cult was associated with a particular kind of soil, suggesting an economic basis for Greek polytheism. Dionysos and

Demeter In ancient Greek religion and mythology, Demeter (; Attic: ''Dēmḗtēr'' ; Doric: ''Dāmā́tēr'') is the Olympian goddess of the harvest and agriculture, presiding over crops, grains, food, and the fertility of the earth. Although s ...

, for example, were gods of farming, Hermes and

Hera In ancient Greek religion, Hera (; grc-gre, Ἥρα, Hḗrā; grc, Ἥρη, Hḗrē, label=none in Ionic and Homeric Greek) is the goddess of marriage, women and family, and the protector of women during childbirth. In Greek mythology, she ...

gods of pastoralists and Apollo and Artemis gods of nomadic hunter-gatherers

Boards

Retallack has served as an associate or technical editor for such scientific journals as ''Geology'', '' PALAIOS'', and ''

Journal of Sedimentary Research The Society for Sedimentary Geology is an international not-for-profit, scientific society based in Oklahoma. It is commonly referred to by its acronym SEPM, which refers to its former name, the Society of Economic Paleontologists and Mineralogists ...

''. His fellowships include the Geological Society of America, and the

American Association for the Advancement of Science The American Association for the Advancement of Science (AAAS) is an American international non-profit organization with the stated goals of promoting cooperation among scientists, defending scientific freedom, encouraging scientific respons ...

. 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.

Critical reception

Early reviews of Retallack's textbooks have been positive. Of ''Soils of the Past'', David Fastovsky concludes "it is requisite for all persons trying to understand paleosols". Of ''A Colour Guide to Paleosols'', Daniel Yaalon concludes "Highly recommended for students and researchers alike for an introductory insight to paleopedology and to whet and refine their skills in paleosol interpretation." Both reviews however baulked at the unfamiliarity of soil science terminology and classification in these texts. Retallack's approach to the description and interpretation of paleosols has been widely adopted. Some controversy concerned use of modern soil taxonomies for paleosols, but Retallack's approach has since been validated by development of additional geochemical proxies for soil taxonomic criteria. Retallack's confirmation of abrupt paleoenvironmental change on land at the Cretaceous-Tertiary and Permian-Triassic boundaries, have been supported by later research on extinction. Retallack's initial taphonomy work interpreting some

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...

biota as lichens was questioned for its applicability to all Ediacaran fossils. The recent Retallack proposal that

fossils were preserved in paleosols and thus could not be marine fossils, is a provocative challenge to prior interpretations, and has been supported in some quarters, but disputed in others. However this hypothesis of Retallack is not universally accepted by the paleontological community. '' Nature'' called it a "controversial claim" in a news report, in which paleontologist Guy Narbonne said "Most of us appreciated that Retallack's lichen hypothesis was innovative thinking and tested his ideas critically, but it 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."

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

Textbooks * ''Soils of the past: an introduction to paleopedology'', 3rd edition, Wiley, Chichester, 2019, * ''A colour guide to paleosols'', John Wiley and Sons, Chichester, 1997, * ''Soil grown tall: the epic saga of life from earth'', Springer Nature, Cham, Switzerland, 2022, Selected publications * * * * * * * *

References

External links

*
Personal web page
* {{DEFAULTSORT:Retallack, Gregory 1951 births American paleontologists University of Oregon faculty American geologists Living people Fellows of the Geological Society of America People from Hobart People educated at The King's School, Parramatta Macquarie University alumni University of New England (Australia) alumni Indiana University alumni Australian geologists Australian paleontologists