Rapid Evolution: New Species Appear 2000 Years After Chicxulub Impact

About 66 million years ago, an asteroid hit the Earth and wiped out almost all life, primarily the dinosaurs, which were the dominant species at the time. Life then evolved again -- at a breathtaking pace, as scientists have discovered.

The asteroid had a diameter of 10 to 15 kilometers. It struck what is now the Yucatan Peninsula in Mexico -- there was water there at the time -- and left behind one of the largest impact craters on Earth, with a diameter of 180 kilometers and a depth of 30 kilometers. Immense amounts of earth were thrown into the air, causing the climate to change drastically. 75 percent of all species died out within a very short time. It was the largest mass extinction in Earth's history.

We see the re-evolution of life today. The new beginning occurred in a geologically very short period: new plankton species already appeared after less than 2000 years, reports a team from the Institute for Geophysics at the University of Texas in the journal Geology about their research at the Chicxulub crater in Mexico. "That's incredibly fast," said Chris Lowery. Normally, new species evolve over a period of about a million years.

When did the species return?

However, Lowery's team had already researched the impact crater earlier and found that life recovered rapidly after the catastrophe. Nevertheless, research assumed that it took several tens of thousands of years for new species to appear.

Sediment accumulations, i.e., loose materials, some of which are organic in origin, are considered an indicator for this. The assumption was that sediments accumulated after the impact at the same rate as before. This was the basis for dating small fossils in the layer, which is referred to as the Cretaceous-Paleogene boundary (K/Pg boundary).

Lowery's team assumes that mass extinctions on land and in the sea changed the sedimentation rate at the K/Pg boundary. It used helium-3 as a marker for dating. The helium isotope is deposited in sediment on the seabed at a constant rate. If the sediment is deposited slowly, it contains a lot of helium-3. If it is deposited quickly, the helium-3 content is correspondingly lower.

Based on the helium-3 content, the team determined the sedimentation rates at six discovery sites of the K/Pg boundary in Europe, North Africa, and the Gulf of Mexico. It then used this data to determine the age of sediments in which Parvularugoglobigerina eugubina occurs. The occurrence of this plankton species is considered an indication of recovery after the mass extinction.

New plankton species after 2000 years

Parvularugoglobigerina eugubina appeared in the period 3500 to 11000 years after the Chicxulub impact -- the exact timing varies by location. However, researchers also found some plankton species that appeared less than 2,000 years after the Chicxulub impact and initiated a recovery of biodiversity that continued for 10 million years.

"The speed of recovery shows how resilient nature is. That complex life is restored in a heartbeat, on a geological timescale, is truly amazing," said Timothy Bralower, one of the study's authors. "Given the threat of anthropogenic habitat destruction, this may also be reassuring for the resilience of modern species."

(wpl)