mammals
edyong | August 15, 2009This article is reposted from the old Wordpress incarnation of Not Exactly Rocket Science.
Twenty-two thousand sounds like a huge number. It's happens to be number of eastern Pacific gray whales currently swimming off the coast of North America. It's certainly much larger than 140, the number of whales that aboriginal people of this area are allowed to hunt. And it's far, far bigger than zero, the population size that the whales were rapidly approaching in the mid 20th century.
Obviously, it's all relative. Twenty-two thousand is still much less than ninety-six thousand. That's the size of…
laelaps | August 14, 2009
A male western gorilla (Gorilla gorilla), photographed at the Bronx Zoo.
The origin of human bipedalism has long been a hot topic among paleoanthropologists. At the very least it is seen as something of a marker for the emergence of the first hominin, yet it remains unclear whether the earliest hominins evolved from a terrestrial, knuckle-walking ancestor or a more arboreal ape. A common interpretation is that since our closest living relatives, gorillas and chimpanzees, are both knuckle-walkers then the first hominins, too, evolved from a knuckle-walking ancestor. As Tracy Kivell and…
edyong | August 13, 2009They say that imitation is the sincerest form of flattery and it appears that capuchins believe it too. These very sociable monkeys gravitate towards humans that mimic their actions, spending more time in their company and even preferring to trade with them.
Annika Paukner, who studied this monkey business, thinks that imitation is a type of social glue that binds groups of monkeys together. It says, "We are alike," and in doing so, it lays the foundation for acts of selflessness by providing a means for two individuals to form an empathic connection.
Certainly, imitation is very much a…
laelaps | August 11, 2009
The skull of a cheetah (Acinonyx jubatus), photographed at the National Museum of Natural History.
laelaps | August 9, 2009
A saiga (Saiga tatarica), photographed at the National Museum of Natural History in Washington, D.C.
laelaps | August 5, 2009I have been writing a lot about extinct proboscideans lately, but when it comes to essays about elephants and their extinct relatives John McKay can't be beat. His latest is about various representations of mammoths locked in ice and is a must-read. (He even references one of the worst movies I have ever seen, Mammoth.) John promises that he has "lots more to say about this topic", too, so keep your fingers crossed for a sequel to his wonderful essay.
edyong | August 4, 2009You'll sometimes hear people lowering their voices to make themselves sound tougher or more commanding. We're not the only ones - it seems that our close relatives, the orang-utans, pull the same trick, and they use tools to do it. Madeleine Hardus from the University of Utrecht has found preliminary evidence that young orang-utans use leaves for deception, in order to make lower-pitched calls that seem to come from a much larger animal.
While many animals are accomplished tool-users, most use their utensils to find food. A few populations of orang-utans, living in Borneo, are the only…
laelaps | July 30, 2009
A restoration of the head of Pyrotherium. From W.B. Scott's A History of Land Mammals in the Western Hemisphere.
I do not remember much from my elementary school education, but there are a few fragments that have stuck with me. One day in 6th grade geography, for example, Mr. McCutcheon asked the class what we thought the continents of South America and Africa looked like. Africa was easy, it looked like the head of an African elephant (northwestern Africa being the right ear and Madagascar the tip of the trunk), but there was a greater diversity of opinion about South America. The…
laelaps | July 29, 2009
Color-coded diagram of a small bone bed containing at least twelve individuals of the Permian synapsid Suminia. From Frobisch and Reisz (2009)
When I hear the phrase "early human relative" I cannot help but think of an ape-like creature. Something like Sahelanthropus fits the bill nicely; it may not be a hominin but it is still a close relative from around the time that the first hominins evolved. That is why I was a bit puzzled to see MSNBC.com parroting a story written by the Discovery Channel which proclaimed "Early human relative predates even dinosaurs"! Was this another fossil that…
laelaps | July 27, 2009
A progressive "march" of elephant evolution as portrayed in Ingersoll's The Life of Animals. From left to right Moeritherium, Palaeomastodon, Gomphotherium ("Trilophodon"), Mammut americanum (American mastodon), Elephas maximus (Asian elephant).
Every now and then I like to browse through old popular-audience books about evolution. Given that I am writing such a popular book myself I enjoy looking back to see how other authors have approached the same task. In some cases I have come away quite impressed, but other times it seems that some authors of old used such platforms to give their…
laelaps | July 24, 2009
A recent restoration of Deinotherium from Markov, et al (2001) "A reconstruction of the facial morphology and feeding behavior of the deinotheres." The World of Elephants, International Congress, Rome 2001. Taken from The World We Don't Live In.
Poor Deinotherium. Although it is one of the most readily recognizable proboscideans (the larger group to which modern elephants belong) it has long been treated as an uninteresting distant cousin of more popular fossil elephants like woolly mammoths. During the early 20th century, especially, it was often seen as something of a failed evolutionary…
edyong | July 19, 2009It seems like an uneven match. In one corner, the unassuming California ground squirrel (Spermophilus beechyi), 30cm in length. In the other, the northern Pacific rattlesnake (Crotalus oreganos), more than twice the length of the squirrel, and armed with hinged fangs that pack a lethal venom. But thanks to a cunning adaptation, the squirrel often gets an unexpected upper hand in this bout.
Ground squirrels live in a series of burrows that keep them out of reach of most predators. Snakes, however, have exactly the right body plan for infiltrating long sinuous tunnels, and it's not surprising…
laelaps | July 19, 2009
A harbor seal (Phoca vitulina), with a common goldeneye in the background, photographed at the Central Park Zoo.
edyong | July 17, 2009
Bats view the world in echoes, timing the reflections of their own ultrasonic calls to navigate and hunt. This biological sonar, or echolocation, has made them masters of the night sky; it's so sensitive that some species take moths and other insects on the wing, while others pluck spiders from their webs without entangling themselves in silk. But with such an efficient technology, it was only a matter of time before their quarry developed countermeasures.
Some insects gained ears; others simply rely on outmanoeuvring their attackers. But one group, the tiger moths, play bats at their own…
laelaps | July 16, 2009
A red fox (Vulpes vulpes), photographed at Prime Hook National Wildlife Refuge, Delaware.
edyong | July 16, 2009Compare the elegant grace of a running wolf with the comical shuffle of a waddling dachshund, and you begin to understand what millennia of domestication and artificial selection can do to an animal. As dachshunds develop, the growing tips of their limb bones harden early, stunting their growth and leading to a type of dwarfism called chondrodysplasia. The same applies to at least 19 modern breeds including corgis, Pekingese and basset hounds, all of which have very short, curved legs.
These breeds highlight the domestic dog's status as the most physically diverse of mammals. Now, a team of…
laelaps | July 16, 2009
A traditional restoration of Platybelodon as seen in H.F. Osborn's 1936 elephant monograph. From Lambert (1992).
Whenever I visit the American Museum of Natural History in New York I make sure to at least pass through the fourth-floor fossil halls before I leave, and one of my favorite displays features the shovel-mouthed proboscidean Platybelodon. In a glass case in the shadow of a mammoth skeleton is a growth series showing the development of the Platybelodon jaw, from juvenile to adult. Like many AMNH displays, however, this series was not a product of the renovation of the fossil halls…
laelaps | July 14, 2009
An illustration of Albert Koch's reconstructed "Missourium", or an American mastodon with a few extra bones.
Even though I find modern creationism to be intensely aggravating I occasionally like to browse older creationist texts. It is amusing to see how old creationist arguments have been recycled ad naseum, refitted for new uses (i.e. acceptance of evolution is responsible for [insert social ill here]), or given up entirely over time. In this latter category falls the assertion of the 19th century biblical literalist Mary Roberts that God had purposefully created, and subsequently…