Evolutionary Biology
neurophilosophy | May 19, 2011Skull of Hadrocodium wui. (Image courtesy of Mark Klinger and Zhe-Xi Luo, Carnegie Museum of Natural History)
THE question of how mammals evolved their exceptionally large brains has intrigued researchers for years, and although many ideas have been put forward, none has provided a clear answer. Now a team of palaeontologists suggests that the mammalian brain evolved in three distinct stages, the first of which was driven by an improvement in the sense of smell. Their evidence, published in tomorrow's issue of Science, comes from two fossilized skulls, each measuring little more than 1cm in…
neurophilosophy | April 28, 2011Ernst Haeckel's Kunstformen der Natur (Artforms of Nature) was a landmark in biological illustration. Published in 1904, it was lavishly illustrated with 100 exquisitely detailed lithographic plates, including this one, showing nine different species of cubomedusae, or box jellyfish.
It has been known, since around the time that Haeckel's masterpiece was published, that box jellyfish have a unique visual system which is more sophisticated than that of other jellyfish species. They boast an impressive set of 24 eyes of four different types, which are clustered within bizarre sensory appendages…
gregladen | January 26, 2011There are human universals. There, I said it. Now give me about a half hour to explain why this is both correct and a Falsehood. But first, some background and definition.
Most simply defined, a human universal is a trait, behavior or cultural feature that we find in all human societies. Men are always on average larger than women. All humans see the same exact range of colors because our eyes are the same. The range of emotions experienced by people is the same, and appears in facial expressions and other outward affect, in the same way across all humans.
The term "Human Universal"…
gregladen | January 6, 2011It is difficult to imagine how point mutations, a large number of which are neutral, a certain number of which are deleterious, and a tiny number of which are fitness-enhancing, can add up to the sorts of evolutionary diversity and adaptive elegance we see in real life. However, there are only two possible explanations for what we see in nature: 1) Evolution happened more or less as we think it did or 2) God created life and made it look exactly like evolution happened. Take your pick. I'm betting on number 1.
People will get mad at me for suggesting that it is hard to figure how all this…
gregladen | January 3, 2011A discussion of misconceptions in evolution ... about missing links, or great chains of being, or teleology (the idea that evolution is goal-directed) has got to be the most fun you can have with your pants on. Pursuant to this, let's sharpen and clarify our evolutionary theory mojo by considering the concept of "mosaic evolution" ... what is it, and what isn't it?
Of course, the concept of mosaic evolution, meant to clarify how evolution works, is often itself misunderstood. From Wikipedia:
"Mosaic Evolution is the concept that major evolutionary changes tend to take place in stages, not…
gregladen | December 2, 2010In his highly readable book, One Long Argument, Ernst Mayr breaks down the body of thought often referred to as "Darwin's Theory" into five separate and distinct theories, the second of which being "common descent." Darwin's second evolutionary theory (second by Mayr's count, not Darwin's) is really a hypothesis that could be worded this way:
All life on earth descended from a single, original, primordial form that arose eons ago.
The evidence in favor of this hypothesis is strong, but the test of the hypothesis ... the means of disproving it, which is, after all, the point of stating it to…
gregladen | October 22, 2010Human infants require more care than they should, if we form our expectations based on closely related species (apes, and more generally, Old World simian primates). It has been said that humans are born three months early. This is not accurate. It was thought that our body size predicted a 12 month gestation, and some suggested that Neanderthals would have had such, but this research conclusion has been set aside based on new analysis. But it is still true that developmentally, human children do not reach a stage of development that allows some degree of self care for a very long time…
gregladen | October 12, 2010Or, when the hunting season is closed, watch teh game (the guys), or when there are no sales, admire each other's shoes (the gals)?
This is, of course, a parody of the sociobiological, or in modern parlance, the "evolutionary psychology" argument linking behaviors that evolved in our species during the long slog known as The Pleistocene with today's behavior in the modern predator-free food-rich world. And, it is a very sound argument. If, by "sound" you mean "sounds good unless you listen really hard."
I list this argument among the falsehoods, but really, this is a category of argument…
gregladen | August 11, 2010The newly reported Saadanius hijazensis may or may not be a "missing link" but in order for this monkey to climb onto the primate family tree, a new branch had to be sprouted. So, not only is Saadanius hijazensis a new species, but it is a member of a new taxonomic Family, Saadaniidae, which in turn is a member of a new Superfamily, Saadanioidea. Why is this important? It's complicated. But not too complicated.
The fossil was found while University of Michigan paleontologist Iyad Zalmout was busy looking for dinosaur fossils in western Saudi Arabia. He found the monkey, from a much…
gregladen | August 10, 2010In Robert Gardner's documentary film Dead Birds, the men of a highland New Guinea village guard the perimeter of the territory, watchful for men of the neighboring group who may be intent on sneaking into the gardens to capture and kill an unwitting child or woman in order to avenge a prior death. But they don't see the men sneaking through the dense riparian forest. They don't even look for them. Rather, they see the birds fly from their preferred habitat where they are foraging or resting, startled into the open by ... something. The birds belie the predator.
Today, in construction…
gregladen | July 28, 2010
The Triassic is old. This book is new. That is a hard to beat combination.
Let's see ... The Triassic is about here:
(You can also look it up in this PDF file supplied by the USGS.
It is situated between two major extinction events, and is especially interesting because it is during this period that modern day ecological systems and major animal groups took a recognizable form. The preceding Permian, if contrasted with modern day, would form a very stark contrast while the Triassic would be at least somewhat more recognizable.
But of course the Triassic was in many ways distinct,…
gregladen | July 22, 2010Remember Evolutionary Psychology? The theory?
It's over.
I think I've told the story elsewhere of having been at the birth of Evolutionary Psychology, down in room 14A in the Peabody Museum. If not, remind me some time and I'll tell it.
Evolutionary Psychology is a particular theory of how the mind works, how evolution has shaped that mind in certain predictable and testable ways, bla di bla di bla and so on and so forth. And, although there is something in there ... something in that theory ... that is useful, it is mostly not really very close to what happens when humans behave. Or…
gregladen | July 10, 2010One of those really cool and useful "evolution stories" gets verified and illuminated by actual research. And blogging!
An oystercatcher is a wading bird of the family Haematopodidae, distributed in one genus, Haematopus. As is the case with many coast loving birds, there has been confusion about the limits of the 11 or so species known to exist worldwide. That itself is an interesting story (Hocke 1996), but one we will not go into now.
Adult coastal oystercatchers (some species are not coastal) eat all sorts of animals found in the intertidal zone, including shellfish of all sorts,…
grrlscientist | July 1, 2010tags: vultures, Gyps species, conservation biology, endangered species, veterinary medicine, toxicology, physiology, evolutionary biology, pharmaceutical chemistry, epidemiology, mathematical modeling, researchblogging.org,peer-reviewed research, journal club
Only thirty years ago, tens of millions of White-rumped Vultures, Gyps bengalensis,
were flying the skies of Asia. They are now classified as Critically Endangered.
Image: Marek Jobda / rarebirdsyearbook.com [larger view]
A zombie is another name for The Walking Dead -- those who are lifeless, apathetic, or totally lacking in…
grrlscientist | April 19, 2010tags: evolutionary biology, evolutionary biogeography, molecular biology, medicine, ectoparasite, orificial hirudiniasis, mucosal leech infestation, hirudinoids, leech, Tyrannobdella rex, public health, zoology, PLoS ONE, anatomy, phylogenetic analysis, taxonomy, researchblogging.org,peer-reviewed research, journal club
Figure 1. Mucosally invasive hirudinoid leeches. Known from a wide variety of anatomical sites including eyes (A) as in this case involving Dinobdella ferox (B), mucosal leech species, as in a case involving Myxobdella annandalei (C), more frequently feed from the…
grrlscientist | April 8, 2010tags: evolutionary biology, behavioral ecology, molecular ecology, personality, novelty seeking, exploratory behavior, dopamine receptor, dopamine receptor D4 gene, DRD4 gene polymorphism, ornithology, birds, Great Tit, Parus major, researchblogging.org,peer-reviewed research, peer-reviewed paper
Bold or cautious? Individuals with a particular gene variant are very curious --
but only in some populations.
Image: Henk Dikkers.
Research suggests that personality variations are heritable in humans and other animal species, and there are many hypotheses as to why differences in personality…
grrlscientist | March 30, 2010tags: evolution, evolutionary biology, UV light, flight, dinosaur, dromaeosaur, theropods, Microraptor gui, paleontology, fossils, birds, researchblogging.org,peer-reviewed research, peer-reviewed paper, journal club
Figure 1. The holotype of Microraptor gui, IVPP V 13352 under normal light. This shows the preserved feathers (white arrow) and the 'halo' around the specimen where they appear to be absent (black arrows). Scale bar at 5 cm. [larger view]
DOI: 10.1371/journal.pone.0009223
It has long been known that when exposed to ultraviolent light, fossilized bones and shells -- and even…
grrlscientist | March 29, 2010tags: evolution, evolutionary biology, behavioral ecology, animal behavior, molecular ecology, parental care, mating systems, monogamy, sexual selection, frogs, poison dart frogs, Dendrobatidae, Ranitomeya, researchblogging.org,peer-reviewed research, peer-reviewed paper, journal club
Peruvian mimic poison frog, Ranitomeya imitator.
Image: Jason Brown [larger view]
To know the breeding system is to know the genetic architecture of a species.
To know the evolution of a breeding system is to know how evolution works ..
~ Lewis & Crowe, Evolution (1955)
Genetic tests have revealed the…
neurophilosophy | March 17, 2010SNAKES have a unique sensory system for detecting infrared radiation, with which they can visualize temperature changes within their immediate environment. Using this special sense, they can image the body heat radiating from warm-blooded animals nearby. This enables them to track their prey quickly and with great accuracy, even in the dark, and to target the most vulnerable parts of the prey's body when they strike. It also warns them of the presence of predators, and may be used to find appropriate locations for building dens.
Infrared detection is known to be mediated by a specialized…
grrlscientist | March 12, 2010tags: evolution, evolutionary biology, gynandromorph, bilateral gynandromorph bird, half-sider, mixed-sex chimaera, sex determination, molecular biology, genetics, developmental biology, endocrinology, birds, chicken, Gallus gallus, ornithology, researchblogging.org,peer-reviewed research, peer-reviewed paper, journal club
Half-sider.
Almost exactly one year ago, hundreds of American birders
were thrilled by sightings and photographs of this remarkable
Northern Cardinal, or Redbird, Cardinalis cardinalis,
photographed in Warrenton, VA.
Image: DW Maiden, 2 March 2009.
I'll never forget the…