Will penguins survive climate change? Their past may reveal the answer
Penguins are evolutionary oddballs millions of years in the making.
Let’s be honest: Penguins are a little, well, weird. They’re flightless birds that waddle around on the coldest reaches of planet Earth, but they can also dive to impressive depths below the ocean's surface, putting them into a strange category of “secondarily aquatic” land animals that have returned to the sea.
But there may be an evolutionary explanation for the penguin’s unique quirks, according to research published this week in the journal Nature Communications. Specifically, penguins may have evolved in response to ancient climate shifts, providing scientists with clues about how well they may adapt to a changing climate today.
“Indeed, our demographic results reveal that penguins have had a complicated history,” write the researchers in the report.
What’s new — The researchers identified key geological events impacting the ways these birds’ bodies adapted to a changing climate, ultimately allowing them to thrive on both land and in water. Their research yielded a few key findings from the penguin’s 60-million-year evolutionary history.
The researchers believe penguins originated in Zealandia — a now-submerged continent off the coast of Australia — before migrating to South America and Antarctica. The penguins likely followed the Antarctic Circumpolar Current, which is a significant ocean current flowing around the globe.
“These adaptations have allowed penguins to colonize some of the most extreme environments on Earth”
The researchers also found that key climate changes profoundly shaped the evolution of penguins, including the diversification of new species. These events include the expansion of Antarctica’s glaciers during the Middle-Late Miocene period roughly 5.3 to 16 million years ago, a period marked by significant global cooling. The expansion of Antarctica’s ice sheets coincides with the emergence of modern crown penguins roughly 14 million years ago.
“Global cooling and major ocean currents appear to be main drivers of penguin diversification and biogeographic patterns,” Chengran Zhou, joint-lead author on the study, tells Inverse. Zhou researches genome evolution and animal adaptation as a bioinformatics technician at the Shenzhen-based biotech company, BGI-Research.
During the Last Glacial Period, also known as the last ice age, which ended around 11,500 years ago, penguins entered into a period of physical isolation at high altitudes due to the expanding ice sheets. After the last ice age ended and Earth began warming up, these isolated penguin species migrated back to the poles, coming into contact with each other again as they recolonized previously abandoned habitats.
Lastly, the researchers found that penguins are truly evolutionary oddballs, differing in both their evolutionary rates and adaptions compared to other bird species. The study calls penguins the “most uniquely specialized” of all living birds.
“Among birds, penguins and their sister group —Procellariiformes, comprising albatrosses and petrels — have the lowest evolutionary rates detected in birds,” Zhou says, adding that the penguins’ lower evolutionary rates may have to do with their adaptations to aquatic ecosystems.
The researchers found a suite of “penguin-specific” genetic adaptations that make these birds so different from their avian counterparts, such as their body size, heat regulation, and diving abilities. Certainly rapidly evolving genes are responsible for increasing bone density, contributing to the iconic flipper wings that penguins use to waddle and swim. Many adaptations, like genes contributing to fat storage, make a good deal of evolutionary sense because they help penguins stay warm in bitterly cold environments.
“These adaptations have allowed penguins to colonize some of the most extreme environments on Earth,” conclude the paper's authors.
But other penguin evolutionary quirks make less sense, such as the lack of genes that make it possible to detect umami tastes, especially since they consume so much umami-rich seafood.
Finally, the scientists identified a link between evolutionary rates and environmental temperature in large-bodied penguins, suggesting that bigger species — think emperor or king penguins — may be better able to adapt to new environments under global warming.
Why it matters — The findings paint a picture of an extraordinary animal that has adapted well to some of the most extreme environments on planet Earth during times of immense climate fluctuations.
“Our study showed that penguins have adapted to the ever-changing world during the last 60 million years,” Zhou says, adding “we are optimistic about penguins’ future.”
But Zhou also cautions that penguins aren’t out of the danger zone. Due to environmental disturbances like climate change, half of all living penguin species are classified as either “Endangered” or “Vulnerable” on the IUCN Red List of Threatened Species. According to the research, the current rates of warming in the Southern Ocean will likely exceed penguins’ natural adaptations.
So while penguins may have evolved in the past to withstand some of the harshest climates, they now stand as “sentinels highlighting the vulnerability of cold-adapted fauna in a rapidly warming world,” the researchers write.
How they made the discovery — Previous studies have looked into penguin evolution, but they only considered a small number of the bird’s genomes from the fossil record, limiting opportunities to study its full evolutionary history.
But in this new research, scientists ambitiously analyzed 27 genomes — comprising all the DNA of an organism — of all living and recently extinct penguin species. Using their DNA dataset and the existing penguin fossil record, researchers then compared the penguin DNA to the genomes of other birds. Their research offers a uniquely comprehensive overview of the penguin’s time on Earth through its genetic profile.
“As such, we present the most comprehensive genomic dataset spanning all modern penguins,” write the researchers.
What’s next — In the next stage of research, Zhou plans to reconstruct the interactions between penguins and their environment, going back several thousand years. This kind of work could help further resolve the “enigmas of penguins,” according to the researcher.
“This study is not the end of the story but a new start,” Zhou remarks.