Timing the colonization of Earth by early life

Written By Elizabeth Catlos

One of my research interests is understanding the timing and driving mechanisms that influenced the evolution of life from marine, lacustrine or otherwise wet environments toward land—evaluating the rate and character of early land colonization by life require precisely dating early land biotas.

Sedimentary rocks exposed in the United Kingdom mark the appearance of significant changes in life in Earth's history. These include the speculated first air-breathing land animal and the first vascular land plants exposed in the rock record. Based on biostratigraphy, which focuses on correlating and assigning relative ages of rock strata using fossil assemblages contained within them, these events occurred in the Silurian times (between 443.7 and 416 million years ago, Ma).

However, rocks containing these critical markers of changes in Earth's history have few absolute, radiometric ages. This missing time limits our understanding of when life began to appear in drier environments on Earth and what drove it to seek these conditions.

We work on remedying this situation by tackling the precise radiometric dating of stratigraphic sections in the U.K. that have recognized the importance of identifying significant biotic changes. To understand rock histories, we extract and date zircon (ZrSiO4), a radioactive mineral common in sedimentary rocks. These critical sections are missing precise radiometric ages and are logical targets for this work.

You can read more about this project in our Nature Research Ecology and Evolution blog post.

Collaborators

Peer-reviewed publications regarding this work:

Catlos, EJ, Mark, DF, Suarez, S, Brookfield, ME, Miller, CG, Schmitt, AK, Gallagher, V, Kelly, A (2020) Late Silurian zircon U–Pb ages from the Ludlow and Downton bone beds, Welsh Basin, UK. Journal of the Geological Society, 178, jgs2020-107. doi:10.1144/jgs2020-107

Suarez SE, Brookfield ME, Catlos EJ, Stöckli DF. A U-Pb zircon age constraint on the oldest-recorded air-breathing land animal. PLoS One. 2017;12: e0179262. DOI: 10.1371/journal.pone.0179262.

Brookfield, ME, Catlos, EJ, Suarez, SE (2020) Myriapod divergence times differ between molecular clock and fossil evidence: U/Pb zircon ages of the earliest fossil millipede-bearing sediments and their significance, Historical Biology. DOI: 10.1080/08912963.2020.1761351

Media coverage regarding this work:

Daily Mail: Ancient Scottish millipede WASN'T the first air breathing land animal, Texas undergrad proves (and scientists admit they now don't know what was), and World's oldest 'bug' is a fossilized 425-million-year-old millipede discovered on a Scottish Island that suggests the ancient creatures evolved from water to live on land in just 40 million years

The Daily Texan: Former Jackson School of Geosciences undergraduate rewrites geological history

Phys.Org: Ancient animal thought to be first air breather on land loses claim to fame

Science Daily.com: Ancient animal thought to be first air breather on land loses claim to fame, and World's oldest bug is fossil millipede from Scotland

Cnet.com: Meet the world's oldest bug, a 425-million-year-old millipede fossil

The Times: Hebridean millipede fossil is ‘oldest bug on Earth

Futurity.org: Millipede fossil takes ‘world’s oldest bug title’

Technology Networks.com: Scottish Millipede Is World's Oldest Bug Fossil

UT Austin, Jackson School Newsletter: Ancient Animal Thought to be First Air Breather on Land Loses Claim to Fame

UT News, Science & Technology, Ancient Animal Thought to be First Air Breather on Land Loses Claim to Fame

UT News, Science & Technology, World’s Oldest Bug is Fossil Millipede from Scotland

Youtube, Paleontologists Find World’s Oldest Fossil Bug

Elizabeth Catlos

Elizabeth Catlos is an Associate Professor in the Department of Geological Sciences at the University of Texas at Austin. Her research interests are in developing and applying new techniques to study Earth dynamics and evolution over time. Most of her research revolves around dating radioactive minerals (geochronology). She uses this and other chemical data from rocks to create models for how major fault systems operated in the past. She has published widely about how fault systems developed in the Himalayas and Turkey, and how mineral ages time significant geological events that occurred in the past. She has journal publications in Science, PloSOne, International Geology Reviews, Journal of Structural Geology, Resources, American Journal of Science, American Mineralogist, among others. She has received funding for her research from the National Science Foundation's International and Tectonics Divisions. She received multiple awards for her research, service, and teaching, including the Geological Society of America's (GSA) Young Scientist Award (Donath Medal), the Knebel Teaching Award for Introductory Course, the Texas Exes Teaching Award, and two outstanding reviewer awards for top-tier journals. She is a GSA Fellow and was invited visiting faculty at UCLA and Heidelberg University (Germany). At UT Austin, she is the Director of the Electron Microbeam Laboratory.

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