Giant Panda's Long-Lost Lineage Discovered From 22,000-Year-Old Specimen In China

A group of scientists exploring China’s Guangxi province found remains of a giant panda that roamed Earth 22,000 years ago but belonged to a different, previously unknown lineage.

Guangxi is not a habitat for pandas, but when the researchers found this specimen in a cave called Cizhutuo, they were totally surprised. The discovery suggested sometime in the distant past, the animals thrived in the region.

But, further analysis revealed this is not the panda we know today and belongs to a completely new group, one that separated from the ancestors of modern-day pandas hundreds of thousands years ago and went extinct later.

The surprising findings were revealed following a thorough analysis of the genetic samples recovered from the specimen.

A research team at the Chinese Academy of Sciences (CAS) extracted mitochondrial (mt) DNA from the ancient cave specimen. Though subtropical environments make preservation and recovery of DNA samples near impossible, the group managed to sequence nearly 150,000 DNA fragments with their sophisticated techniques.

Once the fragments were sequenced, the team aligned them with giant panda mitochondrial genome reference sequence to recover complete mitochondrial genome of the panda in question. Finally, a family tree was constructed using the new genome of the Cizhutuo cave specimen and genomes from 138 present-day bears and 32 ancient bears.

The analysis of that tree confirmed the panda just discovered belonged to a different group, which separated from the ancestors of modern-day pandas sometime between 144,000 to 227,000 years ago. The finding indicated the maternal lineage of the panda was different from that of present-day pandas.

They noted as many as 18 mutations in the DNA sequence of the ancient panda that would have altered the structure of proteins in six mitochondrial genes. Though nothing can be said for sure due to the lack of evidence, the group posits these changes could be the result of the distinct habitat of these animals Guangxi or the climate difference that prevailed during the last glacial maximum period.

“Using a single complete mtDNA sequence, we find a distinct mitochondrial lineage, suggesting that the Cizhutuo panda, while genetically more closely related to present-day pandas than other bears, has a deep, separate history from the common ancestor of present-day pandas,” Qiaomei Fu from CAS, said in a statement.

While not much information is available regarding how pandas have evolved over the years, several fossils recovered from different parts of the world have indicated the animals were once more widespread.

This is why even Fu stressed on the need of conducting similar tests on other ancient panda fossils to get more insight into the animals that existed in the past, how their genetic diversity “changed through time and how that relates to their current, much more restricted and fragmented habitat.”

In the future, they might isolate DNA from the ancient specimen's expansive nuclear genome to delve into its evolutionary as well as shared history with present-day pandas.

The paper titled, “Mitochondrial genome of a 22,000-year-old giant panda from southern China reveals a new panda lineage,” was published June 18 in the journal Current Biology.