How the penguins beat the heat and headed south

Scientists have pieced together some of the evolutionary steps that led penguins to leave tropical climates for Antarctic life over millions of years.

Few animals have evolved to survive the unforgiving Antarctica like penguins. Species like the emperor penguin have overlapping layers of insulating plumage, tight veins to recycle body heat, and just enough belly to withstand wind chills that approach minus 80 degrees Fahrenheit.

With all these adaptations to cold weather, it's hard to imagine penguins living anywhere else. But fossils of ancient penguins have appeared along the equator, and many of these prehistoric seabirds predate the formation of the Antarctic ice sheets. "They experienced some of the hottest times in Earth's history, when it was five degrees warmer at the equator," said Daniel Ksepka, a paleontologist at the Bruce Museum in Greenwich, Connecticut. “They essentially evolved in an ice-free environment.”

To determine how penguins moved from fresh, tropical waters to polar seas, Dr. Ksepka and his colleagues recently analyzed the genomes of all living penguins, including pipsqueaks like the pied-great blue penguin, rarities like the endangered yellow-eyed penguin, and standouts like the yellow-tufted jumping penguin. of modern penguins couldn't tell researchers much. p>

Dr. Ksepka said that more than three quarters of all penguin species "are extinct now". 'will get only a fragment of the hist oire."

To supplement modern data, researchers examined fossils of a motley crew of ancient sailors. Some prehistoric penguins roamed the tropical waters off Peru, using spear-like beaks to spear fish. Others sported long legs, and the tallest might have grown seven feet tall. Some even had rust-red feather patches.

Comparing the genomes of modern penguins with fossil penguins allowed the team to piece together penguin evolution. In their findings, published Tuesday in Nature Communications, the researchers identified genes that helped penguins transition from wading in warm waters to perfecting polar diving. Some of these genes helped the penguins fill up with fat, while others shaped their shriveled wings into streamlined fins. Some have even boosted penguins' immune systems or helped them tolerate low oxygen during deep dives.

ImageAt At the Museum of Natural History in Lima, Peru, paleontologist Rodolfo Salas examined the skull of a giant fossil penguin, which lived 36 million years ago, measured about 1. 50 meters and weighed 130 pounds. Credit... Mariana Bazo/Reuters