A new normal: Study explains universal pattern in fossil record

June 26, 2019

Throughout life's history on earth, biological diversity has gone through ebbs and flows -- periods of rapid evolution and of dramatic extinctions. We know this, at least in part, through the fossil record of marine invertebrates left behind since the Cambrian period. Remarkably, extreme events of diversification and extinction happen more frequently than a typical, Gaussian, distribution would predict. Instead of the typical bell-shaped curve, the fossil record shows a fat-tailed distribution, with extreme, outlier, events occurring with higher-than-expected probability.

While scientists have long known about this unusual pattern in the fossil record, they have struggled to explain it. Many random processes that occur over a long time with large sample sizes, from processes that produce school grades to height among a population, converge on the common Gaussian distribution. "It's a very reasonable default expectation," says Santa Fe Institute Omidyar Fellow Andy Rominger. So why doesn't the fossil record display this common pattern?

In a new paper published in Science Advances, Rominger and colleagues Miguel Fuentes (San Sebastián University, Chile) and Pablo Marquet (Pontifical Catholic University of Chile) have taken a new approach to tackling this question. Instead of trying to only describe fluctuations in biodiversity across all types of organisms, they also look at fluctuations within clades, or groups of organisms that share a common ancestral lineage.

"Within a lineage of closely related organisms, there should be a conserved evolutionary dynamic. Between different lineages, that dynamic can change," says Rominger. That is, within clades, related organisms tend to find an effective adaptive strategy and never stray too far. But between these clade-specific fitness peaks are valleys of metaphorically uninhabited space. "It turns out, just invoking that simple idea, with some very simple mathematics, described the patterns in the fossil record very well."

These simple mathematics are tools that Fuentes, in 2009, used to describe another system with an unusual fat-tailed distribution: the stock market. By using superstatistics -- an approach from thermodynamics to describe turbulent flow -- Fuentes could accurately describe the hard-to-predict dramatic crashes and explosions in value.

"In biology, we see these crashes and explosions too, in terms of biodiversity," says Rominger. "We wondered if Fuentes' elegant approach could also describe the evolutionary dynamics we see in the fossil record."

The team writes that their success opens up new research directions to better understand the evolutionary processes that lead to both stable rates of extinction and speciation at the order- and family-levels of life, and to interruptions that allow for new life forms to emerge.
-end-


Santa Fe Institute

Related Fossil Record Articles from Brightsurf:

How to fix the movement for fossil fuel divestment
Bankers and environmentalists alike are increasingly calling for capital markets to play a bigger role in the war on carbon.

New fossil ape is discovered in India
A 13-million-year-old fossil unearthed in northern India comes from a newly discovered ape, the earliest known ancestor of the modern-day gibbon.

Fossil pollen record suggests vulnerability to mass extinction ahead
Reduced resilience of plant biomes in North America could be setting the stage for the kind of mass extinctions not seen since the retreat of glaciers and arrival of humans about 13,000 years ago, cautions a new study published August 20 in the journal Global Change Biology.

Australian fossil reveals new plant species
Fresh examination of an Australian fossil -- believed to be among the earliest plants on Earth -- has revealed evidence of a new plant species that existed in Australia more than 359 Million years ago.

Tracking fossil fuel emissions with carbon-14
Researchers from NOAA and the University of Colorado have devised a breakthrough method for estimating national emissions of carbon dioxide from fossil fuels using ambient air samples and a well-known isotope of carbon that scientists have relied on for decades to date archaeological sites.

Fossil record analysis hints at evolutionary origins of insects' structural colors
Researchers from Yale-NUS College in Singapore and University College Cork have analyzed preserved scales from wing cases of two fossil weevils from the Late Pleistocene era to better understand the origin of light-scattering nanostructures present in present-day insects.

Reconstructing the diet of fossil vertebrates
Paleodietary studies of the fossil record are impeded by a lack of reliable and unequivocal tracers.

Fossil is the oldest-known scorpion
Scientists studying fossils collected 35 years ago have identified them as the oldest-known scorpion species, a prehistoric animal from about 437 million years ago.

Canadian tundra formerly covered in rich forest: Ancient plant fossil record shows
Canada's northernmost islands, Ellesmere and Axel Heiberg islands in Nunavut, were home to a vibrant, temperate forest 56 million years ago, according to fossil research just published by University of Saskatchewan (USask) scientists.

New Colorado fossil record documents life's rebound after Cretaceous-Paleogene extinction
Nearly 66 million years ago, the reign of dinosaurs ended and the ascendency of mammals on Earth began.

Read More: Fossil Record News and Fossil Record Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.