PhD: The origins of terrestrial biodiversity and the beginning of the second carbon-cycle

This project will investigate a newly discovered lagerstätten that provides an unparalleled insight into life on land one billion years ago.

It is generally considered that life originated in the oceans some 3.5 billion-years-ago from where it diversified with all of the major evolutionary transitions taking place here: origin and diversification of prokaryotes, origins of sex, origin and diversification of eukaryotes, origins of multicellularity etc. Life is believed to have been essentially excluded from the land surface for much of Earth history due to low oxygen levels and insufficient screening from UV-B radiation. Consequently, following the Cambrian Explosion, the oceans teemed with a bewildering diversity and complexity of animal and algal life—while the continents are considered to have been essentially barren.

We have discovered an extraordinarily rich and well preserved fossil biota from the billion-year-old Nonesuch Shale of Michigan, USA that challenges this assumption. The Nonesuch Shale is a very rare example of a terrestrial deposits that is one billion-years-old. It has yielded astonishingly well preserved fossils representing both prokaryotes and eukaryotes—including some that appear to be multicellular.

The aim of this project is to describe and analyse these fossils and use them to interpret the nature of the earliest terrestrial life on the Earth. We have already collected a suite of samples and these will be supplement during fieldwork in Michigan directed by co-supervisor Professor Paul Strother (Boston College). The fossils will be prepared using acid maceration and analysed using light, scanning and transmission electron microscopy. The aim is to document the diversity and shed light on the biological affinities of the fossils. Thus the earliest known terrestrial ecosystems can be reconstructed in terms of their biodiversity and ecology. However, the project will also broach the thorny issue of whether all of the major evolutionary transitions in the history of life took place in the oceans. Is it possible that some of the major events in the early diversification of life took place on the land before migration into the oceans?

The student will also undertake analysis of sediment surface structures in order to ascertain the relationships between early life on land and sediment surfaces. This will employ novel techniques developed by co-supervisor Professor Paul Kenrick (the Natural History Museum, London). By understanding the relationship between early life on land and soil/sediment/rock surfaces, including contribution to biomass, we hope to be able to understand the contribution of these earliest terrestrial ecosystems to weathering, soil formation, biomass burial and hence the origins of the second carbon cycle on planet Earth: the terrestrial carbon-cycle.

The studentship will be based in Sheffield under the supervision of primary supervisor Professor Charles Wellman and utilise the unique facilities of the Centre for Palynology [www.sheffield.ac.uk/aps/staff-and-students/acadstaff/cpnewsletters]. The student will visit the Natural History Museum, London to work with co-supervisor Professor Paul Kenrick on soil/sediment/rock interactions and Boston College, USA to work with co-supervisor Professor Paul Strother (and undertake fieldwork in Michigan).

The student will be trained in diverse palaeontological techniques with a view to pursuing a career in academia (biological or Earth sciences) or industry (e.g. biostratigrapher in the oil industry).