Sunday, November 24, 2013

The mystery of Captain Scott's penguin eggs

, Thursday 21 November 
 
Specimens for scientific study can be extremely difficult to collect, as Captain Robert Falcon Scott learned on his last expedition to Antarctica.
During the past few days, I've been sorting and organising the photographs from my recent trip to London, and shared the above image on twitter. In this photograph, you see a rather large eggshell with a more-or-less rectangular window cut into the shell. According to the museum label that accompanies this specimen, this is one of three emperor penguin eggs that had been collected -- fresh -- by Captain Scott on his last expedition to Antarctica.

But because I had copied the tweet to the Natural History Museum, and because a knowledgeable person was monitoring their twitter feed, I soon learned that the museum tag accompanying this egg shell was not-quite-correct: in fact, Bill Wilson, Apsley Cherry-Garrard and Henry "Birdie" Bowers actually collected this egg in 1911. These three men were part of Captain Scott's last Antarctic expedition.

But that is only a small part of the story. Since emperor penguins breed in the middle of the Antarctic winter, this meant the explorers had to hike 70 miles from Scott's base camp on Ross Island to the penguin breeding colony on Cape Crozier, locate and collect these eggs during the worst possible time: not only was it perpetually dark, but they faced extreme cold, powerful winds and intense blizzards. Why would three well-educated humans knowingly subject themselves to the worst weather imaginable on Earth to collect five fresh penguin eggs -- two of which they accidentally broke during their return journey? Were these guys mad?

These three men might have been mad, but the reason for their five-week-long expedition was not. Penguin eggs were important at that time because they were thought to be integral to confirming a scientific hypothesis popularised by Ernst Haeckel. This hypothesis, famously known as "ontogeny recapitulates phylogeny", proposed that development from a fertilised egg through adulthood re-enacts evolution via stages that resemble the ancient ancestors that gave rise to that particular species:

 
"Ontogeny recapitulates phylogeny." George Romanes' 1892 copy of Ernst Haeckel's controversial -- allegedly fraudulent -- embryo drawings. Romanes' version is often attributed incorrectly to Haeckel. [Romanes, G. J. (1892). Darwin and After Darwin. Open Court, Chicago.] This image is in the public domain due to its age.

This was a controversial hypothesis, but at least some scientists of that time thought they could watch the evolution of bird feathers from reptilian scales by documenting various stages of embryonic development of a primitive bird. At the time, penguins were thought to be the most primitive of birds (actually, this is not true) so this was the rationale for collecting penguin eggs for study instead of, say, chicken eggs.

Eventually, these eggs were added to the collection at the Natural History Museum. Twenty-three years after they had been collected -- after the "ontogeny recapitulates phylogeny" hypothesis had been discredited -- a study was published by zoologist CW Parsons, who concluded that "they did not greatly add to our understanding of penguin embryology."

Although Wilson, Cherry-Garrard and Bowers miraculously managed to return to Scott's base camp with three of the five eggs intact, perhaps most remarkable aspect of this adventure was the mystery that the intrepid explorers had missed: they never noticed that each bird's single precious egg, which was balanced on the parent's feet, was actually being incubated by the father.
Here's a video of Douglas Russell, curator of eggs at the Natural History Museum, telling us a little more of the story about this particular egg:


The pencil drawing of the penguin embryo (above right) is by Dorothy Thursby-Pelham.

NOTE [23 November 2013, Saturday, 0830]: this piece incorrectly stated that the NHM tag on this egg was incorrect. In fact, although captain Scott did not personally collect the penguin eggs, he did make it possible for this to happen by providing access to Antarctica and some information to Wilson, Cherry-Garrard and Bowers about the colony's location. This piece has been amended to correct that inaccuracy.

GrrlScientist can also be found here: Maniraptora. She's very active on twitter @GrrlScientist and sometimes lurks on social media: facebook, G+, LinkedIn, and Pinterest.

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Saturday, November 23, 2013

A Heat Map Of Penguins Explains How They Stay Warm

Penguin heat map
courtesy Université de Strasbourg and Centre National de la Recherche Scientifique (CNRS), Strasbourg, France
As if their home in Antarctica weren’t cold enough, emperor penguins allow their exteriors to drop at least 7°F below their surroundings. The change helps the penguins stay warm, a recent paper showed. When the outer layer of feathers radiates heat to the sky, it becomes colder than its immediate environment, so heat flows back in. The cycle keeps the temperature underneath the plumage constant—and the penguin alive.

This article originally appeared in the December 2013 issue of Popular Science.
This article originally appeared on Popular Science

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Wednesday, November 13, 2013

Did Ancient Climate Change Spur Penguin Evolution?

Photo of a Gentoo penguin on Cuverville Island, Antarctica.
A cooling spell in Antarctica may have helped penguins diversify into the numerous species alive today, such as this Gentoo penguin. Photograph by Paul Souders, Corbis
Ker Than
for National Geographic
Published November 12, 2013

When did the earliest common ancestor of the penguins we know today first waddle the Earth, and why?


The question is surprisingly controversial, and may become more so with a new study suggesting a climate-change connection.

Possible dates for the last common ancestor of living penguins have differed by tens of millions of years. According to DNA evidence, the early ancestor lived some 40 million years ago, while fossil evidence puts the date closer to 10 million years ago.

Now a new genetic study, detailed in this week's issue of the journal Biology Letters, suggests that today's major penguin lineages began diverging from one another about 11 to 16 million years ago, and that their common ancestor first appeared 20 million years ago.

The study also suggests that a prolonged cooling spell in Antarctica may have helped spur penguins to diversify into the 18 species living today.

Reconciling Evidence

The new finding, based on more DNA points than past studies, helps reconcile the genetic and fossil evidence, explained study leader Sankar Subramanian, a postdoctoral student at Griffith University in Australia.

"For the first time we showed a more recent time of origin of penguins, which was in agreement with that based on morphological data," he said.

Intriguingly, the date that Subramanian's team estimates for the diversification of modern penguins coincides with a time 10 to 15 million years ago when scientists think Antarctica underwent a period of rapid cooling that covered the continent in ice.

"So we connected these two dots and speculated [about] a possible relationship," Subramanian said in an email. He cautioned, however, that he and his colleagues "don't have any proof for this connection, which is indeed hard to obtain."

A Mysterious Gap

Paleontologists have found penguin-like fossils dating as far back as 62 million years, tens of millions of years before the first ancestor of today's penguins emerged on the scene.

"The big gap between these two times raises questions like: What happened to the older lineages of penguins? What caused the extinction of all other older lineages? Could that be due to any change in Antarctic or global climate?" Subramanian said.

Subramanian said his team is planning to look next at the molecular signatures of penguins living in very different environments, from the tropical Gal√°pagos Islands to the frozen Antarctic.

"This might reveal valuable information, such as how they could adapt to live in these diverse climates," he said.