Study suggests gaps in fossil record are not a major problem

Fossils are used to piece together the story of evolution, but not all animals and plants become fossils, and many fossils are destroyed before we can find them (for example, the rocks that contain the fossils are destroyed by erosion). As a result, the fossil record is gappy and incomplete, and we lack the data we need to piece together the story of evolution.

A team of sedimentologists and stratigraphers from the Netherlands and the United Kingdom investigated how this incompleteness affects the reconstruction of evolutionary history. To their surprise, they found that incompleteness itself is not a major problem.

“It’s like you’re missing half of a movie. If you miss the second half, you can’t understand the story, but if you miss every other frame, you can still follow the plot without any problem.

“It is the regularity of the gaps, rather than their incompleteness, that determines the reconstruction of the evolutionary history,” says Niklas Hohmann of the Faculty of Geosciences at Utrecht University, who led the study. “If many data are missing, but the gaps are regular, we can still reconstruct the evolutionary history without major problems, but if the gaps become too long and irregular, the results are strongly biased.”

The study is published in the journal Ecology and evolution of BMC.

Since Charles Darwin published his theory of evolution, the incompleteness of fossils has been considered an obstacle to reconstructing the history of evolution from fossils. Darwin was concerned that the gradual change predicted by his theory would not be recognizable in the fossils because of all the gaps.

“Our results show that this fear is unfounded. We know very well where the gaps are, how long they last and what causes them. With this geological knowledge, we can reconstruct evolution hundreds of millions of years ago with unprecedented temporal resolution,” says Hohmann.

Computer simulations of geological processes at time scales longer than those of the historical record can be used to examine the effects of incompleteness. To this end, Hohmann and his team combined simulations of different modes of evolution with carbonate strata deposits to examine the extent to which the mode of evolution can be recovered from fossil time series and how test results vary between different positions in the carbonate platform and multiple stratigraphic architectures generated by different sea-level curves.

“If Darwin could read the paper, he would certainly be relieved: his theory has proven robust to the vagaries of the rock record. The deep-time fossil record – although incomplete – supports our understanding of the mode and pace of evolution,” Hohmann adds.