🌅 Rewriting the Emergence of the Animal Kingdom

SOURCE

Lole Durbin et al. (2026)

WHAT TO KNOW

• A new study by an international team of researchers suggests animals could have emerged between 800 and 700 million years ago, around 200 million years earlier than currently believed. The work challenges a key assumption scientists have used to estimate when the animal kingdom emerged and raises the possibility that animals lived through the extreme conditions of “Snowball Earth.”

WHY IT MATTERS

• Until now, the upper limit for when animals first emerged has been based largely on ancient fossil deposits like the Weng’an Biota in China, a 590-million-year-old deposit that contains fossils of exceptionally preserved microscopic organisms, none of which can be identified as animals. The theory is that since Weng’an and other similarly aged deposits lack animal fossils despite the quality of preservation, animals likely didn’t exist prior to 590 million years ago. To test that upper limit, the authors of the present study examined fossils from the extremely well preserved Kheseen Biota in Mongolia, which contains many of the same organisms as Weng’an and also lacks animal fossils. However, since Kheseen is around 40 million years younger than Weng’an and dates to a time when animals are known to have existed, the researchers argue the lack of animal fossils in the deposits cannot be taken as evidence that animals didn’t exist at that time.

CONNECT THE DOTS

• To arrive at their upper limit, the team carried out a “molecular clock analysis,” which, without getting lost in the weeds, compares genetic differences between living species and fossil records to calculate when common ancestors may have lived. If the researchers’ new timeline is correct—the present study does not actually establish that animals existed 800 million years ago, only that our current scientific understanding needs to be checked—it would indicate that animals emerged before or during the harsh conditions of a “Snowball Earth,” when extreme glaciations may have covered the planet in a blanket of ice and pushed surface temperatures to as low as -50 degrees Celsius.