Evidence of ‘lightning-fast’ evolution found after dino-killing asteroid impact

The asteroid that struck the Earth 66 million years ago devastated life across the planet, wiping out the dinosaurs and other organisms in a hail of fire and catastrophic climate change. But new research shows that it also set the stage for life to rebound astonishingly quickly. 

New species of plankton appeared fewer than 2,000 years after the world-altering event, according to research led by scientists at The University of Texas at Austin and published in Geology.  

Lead author Chris Lowery, a research associate professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences, said that it’s a remarkably quick evolutionary feat that has never been seen before in the fossil record. Typically, new species appear on roughly million-year time frames.  

“It’s ridiculously fast,” said Lowery. “This research helps us understand just how quickly new species can evolve after extreme events and also how quickly the environment began to recover after the Chicxulub impact.” 

Although previous studies that Lowery and his team have conducted on the Chicxulub crater in the Gulf of Mexico have shown that surviving life returned quickly after the catastrophic event, it has been widely accepted that it took tens of thousands of years for the first new species to appear after impact.  

This timeline assumed that sediments accumulated at the same rate after the impact as they did before the extinction. Researchers mark the beginning and end of the extinction with a global geologic layer created by fallout from the impact called the K/Pg boundary. However, Lowery and his co-authors note that the massive die-offs happening on land and sea altered sedimentation rates for the boundary and made this assumption incorrect. 

The decline in the numbers of calcareous plankton that sink to the seafloor, which mostly went extinct, combined with increased erosion from land after the death of most vegetation caused big changes in how quickly sediment piled up in different places. This made it difficult to determine the true ages of small fossils in this layer based on the sedimentation rate alone.  

In their study, the researchers drew on previously published data on an isotope marker present in the K/Pg boundary that provides a more accurate measure of time captured in the geologic layer — and used it to more precisely determine when different species of plankton appear in the fossil record.  

The isotope marker is called Helium-3. It accumulates in ocean sediments at a constant rate. That means if sediment accumulated slowly, it should have lots of Helium-3, and if it accumulated quickly, it should have less Helium-3, which allowed the team to more accurately calculate the passage of time.  

The research team used the more accurate sedimentation rates calculated using Helium-3 from six K/Pg boundary sites from Europe, North Africa and the Gulf of Mexico to mark the age of the sediments where a new species of plankton, a foraminifera called Parvularugoglobigerina eugubina (P. eugubina), first appears. The appearance of P. eugubina is a commonly used marker of recovery following the extinction. 

Lowery’s team found that this plankton evolved between 3.5 and 11 thousand years after the Chicxulub impact, with the exact timing differing across sites. The researchers also identified other plankton species that evolved in this interval, with some appearing fewer than 2,000 years after the Chicxulub impact, kicking off a recovery of biodiversity that would continue over the next 10 million years. 

“The speed of the recovery demonstrates just how resilient life is, to have complex life reestablished within a geologic heartbeat is truly astounding,” said Timothy Bralower, co-author of the paper and professor in the Department of Geosciences at Penn State University.  “It’s also possibly reassuring for the resiliency of modern species given the threat of anthropogenic habitat destruction.” 

Between 10 and 20 new species of foraminifera appeared within about 6,000 years of the impact, according to the research. Paleontologists still debate which should be classified as distinct species. 

This new timeline demonstrates how quickly new species can appear under the right conditions and highlights how even after devastating losses, life can bound back relatively quickly — a few thousand years later new species were already emerging.