By Dr Manabu Sakamoto, palaeontologist, University of Reading
Think of a palaeontologist. What comes to mind? You might be thinking of Sam Neill in the film ‘Jurassic Park’, Ross from the sitcom ‘Friends’, or some white-gloved employee of the Natural History Museum.
Now think of them ‘doing’ palaeontology. You will probably imagine them digging up fossilized bones, extracting ancient DNA from amber, or piecing together a skeleton like some kind of Jurassic jigsaw.
What about doing maths, or poring over a spreadsheet? Probably not. Yet some of the most exciting dinosaur discoveries in our field come not from fieldwork, but from detailed analysis and reanalysis of the data.
Why is that? Well, understanding how and why biodiversity waxes and wanes through Earth history over hundreds of millions of years is a fundamental goal of paleontology and evolutionary biology alike.
I and my colleagues in the Evolutionary Biology Research Group at the University of Reading aim to achieve this goal, not in the field looking for new fossils, but in front of a computer, through rigorous statistical analyses of large and complicated biological data sets.
Throughout the last 200 years, palaeontologists have been adding more information to the greater pool of knowledge, with every new fossil discovery made out in the field and described in meticulous detail. This was the de facto way of understanding the nature of past biodiversity.
While fossils are still important and fundamental to evolutionary studies with a wide focus, it wasn’t until the latter part of the 20th Century that studies on large-scale patterns in biodiversity through time using large databases became common practice. Since then, using such databases with the aid of computers and statistical software, palaeontologists have described and analysed temporal patterns of species diversity (number of species in any time interval) in a variety of fossil groups, including dinosaurs. They have also attempted to explain peaks and troughs in diversity curves with known geological information, such as mass extinction events or major environmental changes.
Simultaneously, evolutionary biologists have taken the opposite approach, by predicting past events using information from living organisms. They are able to reconstruct the evolutionary history and relatedness of living creatures – otherwise known as phylogenetic trees (or tree of life).
Through inferring the timings of when modern species split off from other related species – for example, by using the rate of genetic change – evolutionary biologists can estimate major events in past history. Such an approach has revealed a rapid diversification, with lots of new species appearing in a short time, of modern birds following the mass extinction event that killed off the dinosaurs, 66 million years ago.
My research bridges the fields of palaeontology and evolutionary biology, through the application of statistical methods used by evolutionary biologists – in particular phylogenetic approaches – on palaeontological datasets. This approach adds to the statistical rigour and accuracy of evolutionary methods by incorporating information made available only through fossils. It adds a deep time element to reconstructing past events.
Perhaps more importantly, while the common approach of tracing species diversity through time may be good for describing historical patterns, evolutionary methods can model and predict the underlying processes that generated such patterns observable in the fossil record.
Understanding processes is important if we want to understand how the modern biodiversity came about, and how it changed throughout Earth history. For instance, my recent paper co-authored with Prof Mike Benton (University of Bristol) and Dr Chris Venditti (University of Reading) used an advanced but well established statistical method to model the processes of new species of dinosaurs appearing through time.
This gave us strong evidence to help resolve a decades old debate: were dinosaurs reigning strong until they suddenly met their demise when an asteroid hit the Earth 66 million years ago – or, were they already in decline and were merely finished off by the extra-terrestrial impact?
Our study demonstrated that it was the latter. In doing so, it became one of the most talked-about dinosaur discoveries of 2016 – and without a fossil in sight.
- Dr Manabu Sakamoto is the winner of the University of Reading Research Output Prize for 2017 in the Environment theme, for his work on the paper ‘Dinosaurs in decline tens of millions of years before their final extinction’, published by the journal PNAS in April 2016.
- To date, the paper has been downloaded 46,000 times, and was one of the Top 50 most discussed scientific papers in the world in 2016, according to Altmetric.