Flawed analysis casts doubt on years of evolutionary research

Flawed analysis casts doubt on years of evolutionary research

Studies based on the apparently flawed method have suggested Earth's biodiversity remained relatively stable - close to maximum carrying capacity - and hinted many signs of species becoming rapidly extinct are merely reflections on the poor quality of the fossil record at that time.

However, new research by scientists at the University of Reading suggests the history of the planet's biodiversity may have been more dynamic than recently suggested, with bursts of new species appearing, along with crashes and more stable periods.

The new study, published in Methods in Ecology and Evolution by Dr Manabu Sakamoto and Dr Chris Venditti, from Reading, and Professor Michael Benton, from Bristol, says a technique used to 'correct' records of diversity in fossils is actually giving misleading results.

It means almost a decade's worth of work aimed at providing an insight into evolution may be misleading as it was based on this fundamental error.

The method assumes that variations in the number of different fossils at any given time are a reflection of how much rock was available. It has been used in more than 150 published research papers since it was first used in 2007.

Dr Sakamoto, evolutionary biologist at the University of Reading, said: "Our work calls into question nearly a decade's worth of scientific reports and interpretations on the way life on Earth has evolved.

The researchers ran thousands of simulations to test the data correction method, but found it failed to return correct results in as much as 100% of the simulated cases.

Professor Mike Benton, Earth Scientist at University of Bristol, said: "The core assumption is that any portion of fossil diversity that can be explained by variations in rock volume should be explained by variations in rock volume. This assumption is based on no evidence.

"At the extreme, if you have no rock you get no fossils. However, there are many cases where two time intervals are represented by the same amount of rock worldwide, and yet fossil diversity varies massively. Explain that."

Earlier this year, Dr Sakamoto led research that revealed the dinosaurs were facing extinction even before the astroid strike that is credited with bringing about their ultimate decline.

Quality of the Fossil Record

How good is the fossil record?

The study, led by Dr Alex Dunhill, formerly at the Universities of Bristol and Bath and now at the University of Leeds, explored the rich and well-studied fossil record of Great Britain. Professional geological work has been done in the British Isles for over 200 years and the British Geological Survey (dating from the 1830s) has amassed enormous, detailed knowledge of every inch of the rocks and fossils of the islands.

Together with collaborators from the Universities of Bristol and Bergen, Dr Dunhill compared biodiversity through the last 550 million years of the British fossil record against a number of geological and environmental factors including the area of sedimentary rock, the number of recorded fossil collections and the number of named geological 'formations'. All of these measures have been used as yardsticks against which the quality of the fossil record can be assessed – but the new study casts doubt on their usefulness.

Dr Dunhill said: "We suspected that the similar patterns displayed by the rock and fossil records were due to external factors rather than the number of fossils being simply dictated by the amount of accessible rock. Our work shows this is true. Factors such as counts of geological formations and collections cannot be used to correct biodiversity in the fossil record."

The study benefits from the application of advanced mathematical techniques that not only identify whether two data sets correlate, but also whether one drives the other.

The results show that out of all the geological factors, only the area of preserved rock drives biodiversity. Therefore, the other geological factors – counts of fossil collections and geological formations – are not independent measures of bias in the fossil record.