evolution
awild | April 25, 2009
Pogonomyrmex micans, Santiago del Estero, Argentina
Ants of the genus Pogonomyrmex ("Pogos") are known to myrmecologists as the classic harvester ants of North American deserts. They are conspicuous insects, the most noticeable of the desert ants, and something of a model organism for studies of ecology. Numerous scientific papers on pogos are published each year, and one species- Pogonomyrmex californicus- is mailed to school classrooms around the country to populate those plastic ant farms.
It's easy to forget amidst the celebrated riches of North American pogos that South America…
razib | April 23, 2009There are some papers out on the genome of the domestic cow out right now. ScienceNews has an overview:
Two competing research teams have cataloged the "essence of bovinity" found in the DNA of cattle, but not without disagreement on some essential points.
Reporting online April 23 in Science and April 24 in Genome Biology, the two groups compiled drafts of the bovine genome, identifying genes important for fighting disease, digesting food and producing milk.
I don't see the Genome Biology paper on the site yet, but there are two in Science. First, The Genome Sequence of Taurine Cattle: A…
pharyngula | April 23, 2009
It's yet another transitional fossil, everyone! Oooh and aaah over it, and laugh when the creationists scramble to pave it over with excuses.
What we have is a 23 million year old mammal from the Canadian arctic that would have looked rather like a seal in life…with a prominent exception. No flippers, instead having very large feet that were probably webbed. This is a walking seal.
(Click for larger image)a, Palatal view of skull; b, lateral view of skull and mandible, left side; c, occlusal view of left mandible. Stippling represents matrix, hatching represents broken bone surface. The…
laelaps | April 22, 2009Of all the evolutionary transitions that have ever taken place few have received as much attention as the origin of whales. (See here, here, here, here,and here for a few of my posts on the subject.) The story of how terrestrial hoofed mammals gave rise to the exclusively aquatic leviathans has been highlighted in headlines over and over again, but other marine mammals have not received the same amount of public attention. In the case of pinnipeds (seals, sea lions, and walruses) this may be at least partially due to the fact that their origins have been difficult to tease out.
It has long…
edyong | April 22, 2009
Seals and sea-lions gracefully careen through today's oceans with the help of legs that have become wide, flat flippers. But it was not always this way. Seals evolved from carnivorous ancestors that walked on land with sturdy legs; only later did these evolve into the flippers that the family is known for. Now, a beautifully new fossil called Puijila illustrates just what such early steps in seal evolution looked like. With four legs and a long tail, it must have resembled a large otter but it was, in fact, a walking seal.
Natalia Rybczynski unearthed the new animal at Devon Island, Canada…
pharyngula | April 22, 2009It's another one of those long traveling days for me today. I'm on my way to Oregon (I'm at the airport already, so don't worry about any more accidents!), so I may be a bit quiet for a while. Which means I should put something here to keep everyone in a busy uproar for a while.
My job is done, and Jerry Coyne has done the dirty work for me. He has put up a long post criticizing the accommodationist stance of several pro-evolution organizations, particularly the NCSE.
Among professional organizations that defend the teaching of evolution, perhaps the biggest offender in endorsing the harmony…
edyong | April 21, 2009Nocturnal animals face an obvious challenge: collecting enough light to see clearly in the dark. We know about many of their tricks. They have bigger eyes and wider pupils. They have a reflective layer behind their retina called the tapetum, which reflects any light that passes through back onto it. Their retinas are loaded with rod cells, which are more light-sensitive than the cone cells that allow for colour vision.
But they also have another, far less obvious adaptation - their rod cells pack their DNA in a special way that turns the nucleus of each cell into a light-collecting lens.…
razib | April 21, 2009Neandertal birth canal shape and the evolution of human childbirth:
Childbirth is complicated in humans relative to other primates. Unlike the situation in great apes, human neonates are about the same size as the birth canal, making passage difficult. The birth mechanism (the series of rotations that the neonate must undergo to successfully negotiate its mother's birth canal) distinguishes humans not only from great apes, but also from lesser apes and monkeys. Tracing the evolution of human childbirth is difficult, because the pelvic skeleton, which forms the margins of the birth canal,…
pharyngula | April 20, 2009Jerry Coyne carries out an amusing exercise in reasoning like an evolutionary psychologist: why does human semen taste bad? It turns out that it is really easy to invent all kinds of entirely reasonable rationalizations for it: in particular, it's to promote ejaculation in the orifice that is more likely to result in pregnancy, since women can't get pregnant by way of their stomach. It's all deductively logical, but built on premises floating in thin air, with no empirical foundation at all…the usual flaw on which evolutionary psychology fails.
It does open up all kinds of angels-dancing-upon…
pharyngula | April 20, 2009I was sent this story about genes and IQ, and right from the beginning, my alarm bells were ringing. This is crank pseudoscience.
Gregory Cochran has always been drawn to puzzles. This one had been gnawing at him for several years: Why are European Jews prone to so many deadly genetic diseases?
Tay-Sachs disease. Canavan disease. More than a dozen more.
It offended Cochran's sense of logic. Natural selection, the self-taught genetics buff knew, should flush dangerous DNA from the gene pool. Perhaps the mutations causing these diseases had some other, beneficial purpose. But what?
At 3:…
laelaps | April 20, 2009
A giraffe, photographed at the Bronx zoo.
Why do giraffes have long necks? We know that modern giraffes must have evolved gradually, but figuring out what selection pressures influenced giraffe evolution is another story altogether. One of the most popular recent explanations is that giraffes have long necks as a result of sexual selection.
The "necks for sex" hypothesis is primarily inspired by the contests between male giraffes. In these duels the males stand side by side and whack each other with their necks and ossicones ("horns"). This can be seen in the video below;
What does this…
grrlscientist | April 20, 2009tags: The Beagle Project, science, fund-raising, humor, streaming video
This amusing streaming video, featuring a self-described "fat, bearded chap with a Charles Darwin fixation" whom I know in real life, has an important message: Let's Bring the Magic Back! [1:50]
The Beagle Project aims to celebrate Charles Darwin's 200th birthday by building a sailing replica of the HMS Beagle and recreating the Voyage of the Beagle with an international crew of researchers, aspiring scientists and science communicators (perhaps, including me!). The voyage will apply the techniques of 21st century…
evolvingthoughts | April 19, 2009I sometimes worry about the lack of attention philosophers pay to actual biology, settling instead for purely verbal arguments. I am travelling right now so I don't have time to carefully critique Jerry Fodor's latest attack on "Darwinism", but it seems that he is actually making the argument that natural selection is not selection because there's no agent doing selection, and it's just a metaphor and hence bad science. At the same time as this debate is occurring over on PhilPapers, this piece comes out showing that selection on trout size by bear predation is directional and hasn't yet…
gregladen | April 19, 2009From a University of Chicago Press Release.
The genetic toolkit that animals use to build fins and limbs is the same genetic toolkit that controls the development of part of the gill skeleton in sharks, according to research to be published in Proceedings of the National Academy of Sciences on March 23, 2009, by Andrew Gillis and Neil Shubin of the University of Chicago, and Randall Dahn of Mount Desert Island Biological Laboratory.
"In fact, the skeleton of any appendage off the body of an animal is probably patterned by the developmental genetic program that we have traced back to…
razib | April 19, 2009I long ago noticed that David Sloan Wilson was a contributor to The Huffington Post. My own inclination at this point is still to believe that Wilson pushes too hard for group selection, and on occasion engages in the same sort of rhetorical excess which he accuses his critics, such as Richard Dawkins, of. That being said it is probably a net positive that a scientist manages to get some face time in the mainstream-web media. In any case, he has a series of posts on group selection up.
Truth and Reconciliation for Group Selection I: Why it is Needed
Truth and Reconciliation for Group…
grrlscientist | April 19, 2009tags: Birdbooker Report, bird books, animal books, natural history books, ecology books
"How does one distinguish a truly civilized nation from an aggregation of
barbarians? That is easy. A civilized country produces much good bird
literature."
--Edgar Kincaid
The Birdbooker Report is a special weekly report of a wide variety of science, nature and behavior books that currently are, or soon will be available for purchase. This report is written by one of my Seattle birding pals and book collector, Ian "Birdbooker" Paulsen, and is edited by me and published here for your information and…
razib | April 18, 2009John Hawks has pointed out that the great archaeologist Colin Renfrew has been making the case that our species has been in genomic stasis for 50,000 years. He contends:
The genetic composition of living humans at birth (the human genotype) is closely similar from individual to individual today. That was an underlying assumption of the Human Genome Project and it is being further researched in studies of human genetic diversity. We are all truly born much the same. Moreover a child born today, in the twenty-first century of the Common Era, would be very little different in its DNA -- i.e., in…
sb admin | April 18, 2009...these would be the beetles of choice.
Onthophagus taurus dung beetles,
showing size and horn variation among males.
Dung beetles in the widespread genus Onthophagus sport a bewildering array of horns. Not only do the horns of different species vary in shape, size, and the body part from which they grow, many species show a marked dimorphism within the males.
Consider these two male morphs of O. nigriventris, an African species:
The big guy on the right is a major male, and he does pretty much what you'd expect. He bullies his way around with shows of bravado, guarding his burrows…
sciencepunk | April 16, 2009Scientists have discovered new species of iron-breathing microbes that have lived isolated under an Antarctic glacier for millions of years. The microbes are responsible for the landmark blood-red frozen waterfall at Taylor Glacier.
Researchers theorise that the microbes were trapped by the advancing glacier which eventually sealed them inside their habitat. The microbes have persisted in an extreme environment with no light, no oxygen, extreme cold, and high salinity. They are able to survive by liberating iron from the bedrock with the aid of a sulphur catalyst .
The trapped pool is…
evolvingthoughts | April 16, 2009Elio Schaechter has a nice piece up on the recent success at growing a pure line of Coxellia pathogens, the cause of Q Fever. I have been told that fewer than 10% of all microbes are able to be grown in cell-free media, so perhaps this will be the start of a new set of methodologies. Doing this means that pathogens and other microbes will be able to be sequenced and studied in vitro.