The Cambrian explosion: causes and consequences

This project is available from the academic year 2023/24 onwards.

Theme: Past Life & Environments

Primary Supervisor:

Graham Shields

Earth Sciences, UCL

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Secondary Supervisor:

Nick Lane

Genetics, Evolution and Environment, UCL

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Project Description:

Charles Darwin’s great dilemma was why complex life in the form of fossil animals appear so abruptly in rocks around 520 million years ago (Ma), in what is widely known as the Cambrian explosion. During recent decades, exceptionally preserved animal fossils have been found throughout the Cambrian Period, which began 20 million years earlier, and arguably even through the entire, preceding Ediacaran Period, which directly followed the worldwide ‘Snowball Earth’ glaciations (~715 – 635 Ma). Most of these exceptional deposits were discovered in South China, which possesses the best preserved and dated geological record of the marine environment for this time. In collaboration with Chinese and UK colleagues, and depending on the student’s interests, this project would help towards a higher resolution, four-dimensional (temporal-spatial) picture of the evolutionary history of the earliest animals and their environment using one or more aspects of field geology, geochronology – the dating of rocks, geochemistry – for reconstructing nutrient and the coupled biogeochemical cycle (O and C), and mathematical modelling, in such a way as to test key hypotheses about the effects of animal evolution on environmental stability. Training in field and laboratory skills as well as state-of-the-art modelling and time series analysis would be provided as and when needed. Some of the questions that might be addressed by such an interdisciplinary study include: 1) How did the coupled biogeochemical cycles of C, O, N, P and S change during these evolutionary radiations?; 2) Did environmental factors, such as oxygen levels, or biological drivers, such as the emergence of specific animal traits, determine the trajectory of evolutionary change?; and 3) Did the rise of animals increase the biosphere’s resilience against perturbations? This last question has relevance to today’s biosphere, as the modern Earth system and its stabilising feedbacks arose during the Cambrian radiations.

Policy Impact of Research:

The modern Earth system arose during the Ediacaran-Cambrian radiations, and so deconstructing biogeochemical cycles and their feedbacks through that transition, informed by modelling and excellently preserved rock archives, helps us to understand better which factors are important for the continued stability and resilience of today’s biosphere in the face of perturbation.

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