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The researchers sequenced the genomes of 20 living species and subspecies of penguins.
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July 19, 2022 • 17 minutes ago • 3 minutes reading • Join the conversation A king penguin swims in a pool at the Zurich Zoo on August 15, 2012. Photo by Michael Buchholzer/File Photo/REUTERS
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WASHINGTON — The evolution of penguins from their flying seabird ancestors into flightless inhabitants of the marine environment from frigid Antarctica to the tropical Galapagos Islands is among the wonders of the animal kingdom.
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Researchers on Tuesday offered the most detailed study yet of the history of penguins, dating back to their origins more than 60 million years ago, including the identification of a set of genes critical to adaptations related to underwater vision, long dives, regulation of body temperature, diet and body size.
The researchers sequenced the genomes of 20 living species and subspecies of penguins. Since more than three-quarters of known penguin species are now extinct, the researchers also included 50 fossil species in their analysis using skeletal data.
The researchers said penguins evolved from a common ancestor shared with a group of seabirds that includes albatrosses and petrels. Penguins first developed the ability to dive, like the puffin, and subsequently lost their ability to fly when they adapted to the aquatic environment, becoming excellent swimmers and divers.
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The earliest known penguin—dating back 61 million years, about 5 million years after the mass extinction event that killed the dinosaurs—is called Waimanu manneringi from New Zealand.
Emperor penguins are seen in Dumont d’Urville, Antarctica, April 10, 2012. Photo by Martin Passingham/File Photo/REUTERS
“To me, penguins are a perfect example of a major evolutionary transition, like the evolution of an aquatic lifestyle in whales or flight in bats,” said avian paleontologist Daniel Ksepka of the Bruce Museum in Greenwich, Connecticut, who co-authored the study published in the journal Nature Communications .
“We know that penguins evolved from flying birds, but that happened more than 60 million years ago, and we need to look at the fossil record to understand where, when and how that happened. Plus, penguins are ridiculously adorable creatures. They love, they fight, they steal, and because of their funny upright posture, it’s very easy to imagine that they have the same motivations as humans,” Ksepka said.
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The study illustrates how global temperature changes – swings between cold and warm periods – and changes in major ocean currents are important drivers of penguin evolution.
“We calculated how the populations of each penguin species fluctuated over the past 250,000 years based on the imprints left in their genome by population crashes and booms,” Ksepka said. “Growing and shrinking ice sheets have had a major impact on penguins, and species vulnerable to sea ice retreat may suffer significantly from future global warming.”
Penguins were also found to show the lowest rates of evolution ever found among birds.
Penguins live mostly in the southern hemisphere, including species such as the Adélie penguin along the Antarctic coast. The Galapagos penguin is the only one found north of the equator.
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University of Copenhagen postdoctoral fellow and lead author of the study Theresa Cole said the research has uncovered a variety of genes that are likely involved in the penguins’ unique physiological adaptations.
They show gene mutations that shift their vision toward the blue end of the color spectrum. Blue light penetrates deeper into the ocean than light at the red end of the spectrum, so this feature helped fine-tune the vision for sharpness underwater in low light.
In penguins, genes are active that help birds recognize salty and sour tastes. But the genes that help detect bitter, sweet and spicy tastes are disabled. They may no longer be necessary, as penguins forage in cold, salty water and usually swallow prey whole, including fish, shrimp and squid.
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Penguins demonstrate a flattening and hardening of their wing bones and a reduction of their flight feathers into small structures that help turn the wings into flippers. They also reduce air spaces in the skeleton and increase bone wall thickness to increase diving efficiency, as well as adding the ability to store more oxygen in their muscles for long dives.
Penguins were once much larger than today’s species. One species, Kumimanu biceae, which inhabited New Zealand between 55 and 60 million years ago, was about 6 feet (1.8 meters) tall. The largest extant species, the emperor penguin, is about 3 feet (1 meter) tall.
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