Laelaps

Q: How do you sex a Smilodon? (A: Very carefully)

Mon, 09 Nov 2009 12:31:51 -0500

A very lion-like Smilodon, from Ernest Ingersoll's The Life of Animals (1907).

For decades after its discovery the saber-toothed cat Smilodon fatalis was depicted as little more than a lion with a short tail and long fangs. Given its size and habits as a large carnivore the connection appeared to make sense, but recent studies have suggested that Smilodon was quite different from the "king of the beasts." Not only did Smilodon have a face that probably would have looked a bit saggy when compared to modern lions, but a new study published in the Journal of Zoology suggests that male and female Smilodon fatalis did not differ that much from each other.

In order to document variability and parse the differences between males and female Smilodon, however, scientists Julie Meachen-Samuels and Wendy Binder required a considerable sample of bones from the extinct carnivores. This can be troublesome with predators as they are usually relatively rare compared to their prey in the fossil record, but predator traps such as the La Brea tarpits in modern-day Los Angeles, California provide scientists with the unique opportunity to study a large number of predators that were all drawn to one place. Numerous carnivores are preserved at the La Brea site, from modern black bears to the extinct dire wolf (the most common carnivore at the site), but among the most numerous predators found are Smilodon fatalis and the "American lion" Panthera leo atrox. These extinct cats are the primary subjects of the new study, and the researchers wanted to compare lower jawbones from both cats to the same bones from modern lions to see if there were significant differences between males and females in each species.

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Photo of the Day #758: Sand flies and brine shrimp

Mon, 09 Nov 2009 05:13:14 -0500

Sand flies (black bits) and brine shrimp (pink bits) at the edge of the Great Salt Lake. Photographed at Antelope Island, Utah.
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Photo of the Day #757: Rock squirrel

Sun, 08 Nov 2009 08:05:11 -0500

A rock squirrel (Spermophilus variegatus), photographed at Dinosaur National Monument, Utah.

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Photo of the Day #756: American avocets

Sat, 07 Nov 2009 07:48:12 -0500

American avocets (Recurvirostra americana), photographed at Antelope Island, Utah.

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Photo of the Day #755: Dire wolf

Fri, 06 Nov 2009 06:22:47 -0500

The skeleton of a dire wolf (Canis dirus), photographed at the Utah Museum of Natural History in Salt Lake City.

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Where's My Elephant?

Thu, 05 Nov 2009 14:41:07 -0500

Almost every time I get into a discussion about woolly mammoths with someone the conversation eventually steers towards the topic of cloning a mammoth. "Wouldn't it be fascinating?", they often say. And with a little extra genetic engineering, many of my friends hope, maybe someone could create a breed of domesticated mini-mammoths that would definitely be in the running for the title of "Cutest Pet Ever" (at least until they left a mess on the carpet).

The possibility of housebroken mammoths, or at least mammoths in public zoos, seemed within reach in the spring of 1984. It was at that time that there appeared a curious article entitled "Retrobreeding the Mammoth" by Diana ben-Aaron in MIT's Technology Review. It announced that a woolly mammoth, or at least something so close to one that the public would exclaim "I can't believe it's not a mammoth!", had been successfully created through some dazzling scientific knowhow.

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Photo of the Day #754: Giant bison

Thu, 05 Nov 2009 06:15:38 -0500

The skeleton of a giant bison (Bison latifrons), photographed at the Utah Museum of Natural History in Salt Lake City.

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The March of Progress Has Deep Roots

Wed, 04 Nov 2009 13:50:45 -0500

A simplified, silhouette version of the "March of Progress."

The "March of Progress", the iconic evolutionary image of an ancestral ape transforming into a proud, tool-wielding human, is not going anywhere. There is perhaps no other illustration that is as immediately recognizable as representing evolution, but the tragedy of this is that it conveys a view of life that does not resemble our present understanding of life's history. Stephen Jay Gould addressed this two decades ago in his book Wonderful Life, in which he wrote;

Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress. Most people may know this as a phrase to be uttered, but not as a concept brought into the deep interior of understanding. Hence we continually make errors inspired by unconscious allegiance to the ladder of progress, even when we explicitly deny such a superannuated view of life.

Yet the imagery is just too good to resist, and our continual desire to know whether this or that fossil was ancestral to another keeps us thinking in terms of evolutionary "ladders." (A hominin clearly not ancestral to us such as Paranthropus robustus, for example, will never be as celebrated as one that might be closer to our ancestry.) The "March of Progress" is even more useful in terms of satire. What better way to show how backward or primitive your opponents are than to slot them early into the ape->human sequence or show them stamping in the opposite direction of "progress"?

Science historian Constance Areson Clark has recently reviewed the occurrence of this kind of imagery in a new paper published in the journal Isis entitled "'You Are Here': Missing Links, Chains of Being, and the Language of Cartoons." It is not just about the "March of Progress", nor does it mention its modern manifestations, but Clark does provide a few examples of how evolution was depicted in a non-Darwinian fashion. As it turns out, the "March of Progress" has pretty deep roots.

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Photo of the Day #753: Goniopholis

Wed, 04 Nov 2009 06:27:52 -0500

A restoration of the crocodyliform Goniopholis scavenging a stegosaur carcass. Photographed at the Museum of Ancient Life at Thanksgiving Point, Utah.
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Photo of the Day #752: Skeletonized trees

Tue, 03 Nov 2009 06:35:04 -0500

A stand of dead trees near Artists Paint Pots in Yellowstone National Park.
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Chipping Away at Written in Stone

Mon, 02 Nov 2009 14:52:47 -0500

It has been a little more than a month since I announced my forthcoming book on paleontology and evolution, Written in Stone, and I have been hard at work on the manuscript. As it stands now the book is about 3/4 complete. Provided everything stays on schedule I should have a first draft of the whole book finished in about a month.

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Photo of the Day #751: Bison

Mon, 02 Nov 2009 06:15:07 -0500

A bison (Bison bison) photographed on Antelope Island, Utah.

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Photo of the Day #750: Dactylioceras

Sun, 01 Nov 2009 10:44:33 -0500

A slab containing many specimens of the Jurassic ammonite Dactylioceras. Photographed at the Museum of Ancient Life at Thanksgiving Point, Utah.
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Photo of the Day #749: Dinosaur National Monument

Sat, 31 Oct 2009 09:42:16 -0500

Dinosaur National Monument, Utah. The glass building houses the famous fossil wall and will soon be replaced with a new permanent visitor center.
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Book Review: Evolution: The Story of Life

Fri, 30 Oct 2009 15:01:50 -0500

Whenever I sit down to write an entry for this blog I remind myself that I might not always speak the same language as the people I am trying to reach. A statement that might be technically accurate, such as "Mammuthus primigenius was a Late Pleistocene proboscidean with a Holarctic distribution", will likely cause nonspecialist readers to go cross-eyed and vow never to visit this blog again. Instead I have to remember what it was like when I began to teach myself about paleontology and evolution. What do those words mean? And how can I quickly and accurately define them without sacrificing the story I am trying to tell?

Admittedly I sometimes forget this principle. I might throw around terms like "Miocene" or "adapid" without fully explaining their meaning. Thankfully Google is always available to assist baffled readers with defining these terms, but regular readers of this blog (and others like it) might find it easier to keep a single source at hand. When it comes to paleontology and evolution there is no shortage of such titles. This year alone has seen the publication of Evolution: The First Four Billion Years, Darwin's Universe: Evolution A to Z, and Prehistoric Life: The Definitive Visual History of Life on Earth, with Douglas Palmer and Peter Barrett's Evolution: The Story of Life due out early next month. This review is about the latter book, an updated version of the classic "Life Through the Ages" treatment.

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