Darwin considered the incompleteness of the fossil record as the greatest challenge to the theory of evolution. Earth’s sedimentary archives are so full of gaps that most evolutionary events are lost, and our record of past diversity comprises only rare instances of preservation. Evolutionary biology has struggled to recover conclusive information from the fossil record. The ultimate way of making sense of past and present diversity are evolutionary trees: they allow reconstructing relationships between taxa and contribute to understanding processes that lead to their originations and extinctions. These trees are necessary to identify what environmental conditions increase extinction risk or which traits allow organisms to colonize new environments or adapt to change. However, phylogenetic trees are constructed almost exclusively from genetic and morphological data of living or fossilized organisms. To be included in a tree, a species must be preserved in the first place, then discovered, described, and identified. Similarly, the geological information in what environments and at what time in the Earth’s history these species occurred, which could inform us on the environmental context of past evolutionary events, is disregarded in the construction of phylogenies. Recent studies demonstrate that exclusion of fossil data leads to erroneous estimates of extinction rates and distorts recovered evolutionary relationships. At the same time, we have made substantial progress in understanding the structure of the rock record, and quantitative models predicting the distribution of stratigraphic gaps have become available. This project bridges stratigraphic knowledge and phylogenetic inference to include the breadth of geological expertise in evolutionary reconstructions.
We develop a predictive framework of how gaps in the geological record are distributed and how they affect reconstructions of evolutionary processes at the highest resolution. Long-term trends in past diversity can be predicted from the volume of preserved sedimentary rocks, but until now such predictions addressed only (multi)millenial breaks spanning 1 Myr -10 Myr, corresponding to major tectonic events. Such gaps are easy to detect thanks to their broad geographic range, but too long to reveal mechanisms of evolution. Shorter gaps are much more frequent and more relevant for evolutionary processes, but harder to detect. They represent the same time scale as evolutionary events happening at the population and species level. Resolving them will allow this project to reconcile evolutionary processes observable at human timescales, i.e. gradual shifts in populations, with long-term evolutionary processes accessible to us through the fossil record.
Objectives
1. Identify quantitative constraints on evolutionary reconstructions due to incomplete record
2. Create a toolbox to identify drivers of stratigraphic completeness
3. Reconstruct evolution at the 10 000 - 100 000 years scale from empirical geological data
Impact
Why are evolutionary processes inferred from living organisms always different from those inferred from fossils? MindTheGap will obtain unbiased answers from the fossil record on what mechanisms drive major extinctions and diversifications and how we can use past evolutionary events to predict adaptations. Are the geological and fossil records systematically biased? If yes, how? MindTheGap will focus on carbonates, but the understanding of the structure of the geological record developed in this project will be transferable to other environments. It will reveal how well past conditions are archived in the rock record: what biotic and abiotic environments are we missing from times of low sea level or low sediment production?
