anatomy
gregladen | March 29, 2008The question is basic: Is evolutionary change largely random or is it more often shaped by selective forces? The former is linked to what is called Neutral Theory, and it has a lot of support, to the extent that it most likely true. The latter is part of what is sometimes known as the Adaptationist Program, and it is certainly correct. New research on the Development of the Nematode Vulva is sure to cloud the issue even further..
First, a word on this confusing introduction. We know that when we observe life, we do not see a really wide range of degree of adaptation among closely related…
gregladen | March 27, 2008The ape human split is a bit of a moving target. In the 1970s and early 1980s, there were geneticists who placed it at very recent (close to 4 million years ago) and palaeoanthropologists, using fossils, who placed it at much earlier. During the 1980s, the ape-human split moved back in time because of the importance of sivapithecus, then later in time when Sivapithecus slipped and fell out of the hominid/hominin (human ancestor) family tree. Meanwhile the geneticists were moving towards a more and more recent split. At one point not too long ago, all the evidence converged with the split…
edyong | March 14, 2008Crocodiles and alligators are the epitome of stealth. They can wait motionlessly for prey on the surface of the water, dive to the bottom, or roll around the length of their bodies, all without creating a single ripple.
This sneaky manoeuvrability is all the more impressive for the fact that a crocodilian can pull it off without moving its legs or tail. It's particularly difficult because a waiting crocodilian has to move slowly and methodically, and must make do without the helpful forces of lift and drag that accompany faster movements.
Now, for the first time, we know how they do it. They…
gregladen | March 6, 2008There is a new paper out suggesting that the Flores hominids, known as Hobbits, were "human endemic cretins."
From the abstract of this paper:
... We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including…
gregladen | March 3, 2008A colleague and grad student of mine, Rob, just sent me the following question, slightly edited here:
A student in my intro class asked me a good question the other day to which I had no answer. When did smiling cease to be a threat gesture? I have a couple of ideas. One is that with reduced canines, smiling became a way to say "look, I have small canines, I am not a threat to you." The other is that smiling is based more on a "fear-grin" than a threat. Under this idea, smiling might have been a way of showing deference to others. If everyone shows deference, it would be egalitarian, until…
gregladen | February 19, 2008
Fallback foods are the foods that an organism eats when it can't find the good stuff. It has been suggested that adaptive changes in fallback food strategies can leave a more distinct mark on the morphology of an organism, including in the fossil record, than changes in preferred food strategies. This assertion is based on work done by the Grants and others with Galapagos Island finches, by Richard Wrangham and me with hominids, and by Betsy Burr and me with rodents.
The reason for this is simple. There is a rough correspondence between how much energy one can obtain from a food type and…
gregladen | February 19, 2008Comparing living chimpanzees to living humans, in reference to the species that gave rise to these two closely related species, is one way to frame questions about the evolution of each species.
Generally, it is useful to address evolutionary questions by comparing two living species with the reconstructed "last common ancestor" (LCA) of those species. All of the similarities and differences between the LCA and the living form, in each lineage, represent evolutionary "stories" (that could even be worked out as hypotheses). Similarities indicate important, long-maintained adaptations, and…
gregladen | February 11, 2008There is an updated version of this post here: "Is Blood Ever Blue, Science Teachers Want To Know!"
Why ask the question, "Is blood ever blue?"
According to one of the leading experts on the human circulatory system, blood flowing through veins is blue.
I'm not going to mention any names. All I'll say is this: A person I know visited a major research center last year and saw a demonstration of organ removal and some other experimental stuff. A person also visiting asked the famous high-level researcher doing this work "Is blood ever blue?" What he said was not recorded in detail, but it…
gregladen | January 26, 2008... but it might be a sexual organ...
The Federal Communications Commission has proposed a $1.4 million fine against 52 ABC Television Network stations over a 2003 broadcast of cop drama NYPD Blue....The fine is for a scene where a boy surprises a woman as she prepares to take a shower. The scene depicted "multiple, close-up views" of the woman's "nude buttocks" according to an agency order issued late Friday.
...
The agency said the show was indecent because "it depicts sexual organs and excretory organs , specifically an adult woman's buttocks."
The agency rejected the network's argument…
gregladen | January 25, 2008UC Berkeley biologist Robert Full shares his fascination with spiny cockroach legs that allow them to scuttle at full speed across loose mesh and gecko feet that have billions of nano-bristles to run straight up walls. His talk, complete with wonderful slow-mo video of cockroach, crab and gecko gaits, explains his goal of creating the perfect robotic "distributed foot."
gregladen | January 22, 2008Pilobolus dance company members Otis Cook and Jennifer Macavinta perform the sensuous duet "Symbiosis." Does it trace the birth of a human relationship, or the co-evolution of a pair of symbiotic species? That's left for you to decide. Gorgeous, organic choreography blurs the boundaries between the two performers, who use the body's own geometry to lift, move and combine. The music, recorded by the Kronos Quartet on Nonesuch Records, is a compilation of works: "God Music" from Black Angels by George Crumb, "Fratres" by Arvo Pärt, and "Morango ... Almost a Tango" by Thomas Oboe Lee.
gregladen | December 19, 2007Homo floresiensis more widely known as the "Hobbit," may have had arms that were very different from those of modern humans.
A paper in the current issue of the Journal of Human Evolution explores the anatomy of H. floresiensis. To explore this we first have to understand the concept of "Humeral torsion." Humeral torsion is the orientation of the humeral head relative to the mediolateral axis of the distal articular surface. Don't bother reading that sentence again, I'll explain it.
The humerus is the upper arm bone, that runs between your shoulder and your elbow. The humeral head is…
gregladen | December 18, 2007From Scientific American, a piece on the "Cooking Hypothesis" (which yours truly helped develop some years back).
Our hominid ancestors could never have eaten enough raw food to support our large, calorie-hungry brains, Richard Wrangham claims. The secret to our evolution, he says, is cooking
Cooking does indeed turn a lot of stuff that is not edible to humans (or any primate) into usable energy. We think the increase in body size that comes along with the genus Homo (with Homo erectus and kin) is itself a biological signal of cooking.
The problem with his idea: proof is slim that any…