natural selection
gregladen | February 12, 2009Mark Pagel, evolutionary theorist extraordinaire, has published an Insight piece in Nature on Natural selection 150 years on. Pagel, well known for myriad projects in natural selecition theory and adaptation, and for developing with Harvey the widely used statistical phylogenetic method (and for being a reader of my thesis) wishes Charles Darwin a happy 200th birthday, and assesses this question:
How has Darwin's theory of Natural Selection fared over the last 150 years, and what needs to be done to bring this theoretical approach to bear as we increasingly examine complex systems,…
gregladen | February 12, 2009In 1833, Darwin spent a fair amount of time on the East Coast of South America, including in the Pampas, where he had access to abundant fossil material. Here I'd like to examine his writings about some of the megafauna, including Toxodon, Mastodon, and horses, and his further considerations of biogeography and evolution.
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In the vicinity of Rio Tercero...
Hearing ... of the remains of one of the old giants, which a man told me he had seen on the banks of the Parana, I procured a canoe, and proceeded to the place. Two groups of immense bones projected in bold relief from the…
gregladen | February 11, 2009Everyone knows about Darwin's Finches, of the Galapagos Islands. But of course, Darwin made observations of birds throughout his travels on The Beagle. Here, I present a number of passages from The Voyage that include some of these observations.
Struthio Rhea
I will now give an account of ... the Struthio Rhea, or South American ostrich. This bird is well known to abound over the plains of Northern Patagonia, and the united provinces of La Plata. It has not crossed the Cordillera; but I have seen it within the first range of mountains on the Uspallata plain.... The ordinary habits of the…
gregladen | February 10, 2009Charles Darwin wrote a book called Geological Observations on South America. Since Fitzroy needed to carry out intensive and extensive coastal mapping in South America, and Darwin was, at heart, a geologist more than anything else (at least during the Beagle's voyage), this meant that Darwin would become the world's expert on South American geology. Much of The Voyage is about his expeditions and observations. Part of this, of course, was figuring out the paleontology of the region.
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Bahia Blanca is a port at the northern end of Patagonia. Chapter V of The…
gregladen | February 9, 2009We're half way through Darwin Month, and only a tiny ways through the voyage. Need to hurry up! So, let's skip ahead a bit and hit the Gauchos....
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Well, you don't really want to hit at Gaucho ... they hit back rather hard....
The Gauchos are the cowboys of the so-called Southern Cone and Pampas. The Gauchos are a Latin American version the horse mounted pastoralists that emerge wherever four things are found together: Grasslands, horses, people and cattle. Like all horse-mounted pastoralists, they have been known to have certain cultural tendencies or…
gregladen | February 9, 2009Eventually, the Beagle headed south to the area of Uruguay and Argentina, still on the Atlantic Coast, where extensive mapping of the coastal waters was required.
The Parana and Uruguay Rivers meet in the Atlantic estuary known as Rio de la Plata. On the north side of this huge body of water is Montevideo, Uruguay, and on the south side, the northern coast of Argentina. There is an interesting story linked with early European exploration of this area. A Spanish ship is the first known European craft to explore La Plata. The ship's captain and a small crew went inland, and never came…
jwhitfield | January 23, 2009Up until now, our route into the theory of evolution by natural selection has been all downhill. One thing has led effortlessly to another, with Darwin giving the occasional nudge to steer things in the right direction. Not any more. If it's human interest you're after -- doubt, sweat, anxiety -- then chapter 6 of the Origin, 'Difficulties on Theory', is the one you've been waiting for.
I obviously wasn't going to admit it, but after chapters 4 and 5, I was beginning to fear that we'd peaked with the struggle of chapter 3. But this chapter is full of gems, both in the science, and in the…
jwhitfield | January 19, 2009Mathematicians and physicists speak of a result 'falling out of the equations', implying that if you set things up properly, the rest takes care of itself. Chapter 4 of the Origin, 'Natural Selection', is where evolution falls out of the machinery that Darwin has spent the three previous chapters assembling.
And I hate to say it, but it's a bit of an anticlimax.
In retrospect, it's difficult to see how it could be otherwise. Darwin has manoeuvred us into position so carefully, showing the power of artificial selection, the mutability of species and nature's cutthroat struggle, that we're…
gregladen | January 12, 2009Homeschool Showcase (Formerly The Carnival of Cool Homeschoolers) #15 is up at Weird, Unsocialized Homeschoolers. I've got an item listed in the carnival, which is typical (I often send potentially useful science content material to the homeschooling carnivals.)
While you're studying Earth science, you may want to check out Nature's Evolutionary Gems posted by Greg Laden at Greg Laden's Blog. It's up to you whether you use it to teach evolution as fact or as a teachable moment as you discuss God's creation. I know how we'll be using it. ;-)
Wink wink indeed!
gregladen | December 5, 2008Allen's Rule. One of those things you learn in graduate school along with Bergmann's Rule and Cope's Rule. It is all about body size. Cope's Rule ... which is a rule of thumb and not an absolute ... says that over time the species in a given lineage tend to be larger and larger. Bergmann's Rule says that mammals get larger in colder environments. Allen's Rule has mammals getting rounder in colder climates, by decreasing length of appendages such as limbs, tails and ears.
All three rules seem to be exemplified in human evolution. Modern humans tend to be larger and rounder in cooler…
gregladen | November 14, 2008The paper I'm about to discuss is a minefield of potential misconceptions that arise from the way we often use language do describe natural phenomena. This is a situation where it would be easier to start with a disclaimer ... a big giant obvious quotation mark ... and then use the usual misleading, often anthropomorphic language. But I don't think I should do that. We'll address this research the hard way, but the result will be worth the extra work.
Here is the basic hypothesis. The null model is that genetic variation arises randomly and this variation is the raw material on which…
gregladen | November 12, 2008It is hard to kill fungus. Well, not really. They can't handle being burned and chlorine does them in and lots of other chemicals are bad for hem. But when a fungus infects a person ... like with Aspergillos, an infection with Aspergillus in the lungs, fungi are tricky. To kill an infectious agent, one typically poisons it somehow, but to ingest, inject, inhale, or even topically apply a chemical may also affect the person. The reason it is relatively easy to kill an infecting bacterium than it is to kill an infecting fungus is, in part, because fungi are phylogenetically more closely…
gregladen | October 13, 2008 A very good day of grunting worms. Credit: Ken Catania So-called Gene-Culture Co-Evolution can be very obvious and direct or it can be very subtle and complex. In almost all cases, the details defy the usual presumptions people make about the utility of culture, the nature of human-managed knowledge, race, and technology. I would like to examine two cases of gene-culture interaction: One of the earliest post-Darwinian Synthesis examples addressing malaria and sickle-cell disease, and the most recently published example, the worm-grunters of Florida, which it turns out is best explained…
gregladen | August 25, 2008I am currently reading Charles Darwin (Blackwell Great Minds), and so far I mainly like it.
Ruse, as you may know, is a philosopher, something of a science historian, and a science writer who has criticized what he calls "strident" atheism for being too fundamentalist. So that is as annoying as hell. The volume at hand has a large chapter on this issue, and if you read it not knowing about this earlier debate, I think you would come away not being too annoyed, and might even enjoy it, if you consider yourself a .. ahem ... 'strident' atheist. It is annoying, however, that Ruse places "…
gregladen | July 22, 2008Plants and their herbivores have an interesting and complex relationship. It has been true for quite some time (many tens of millions of years) that terrestrial plants do not move around while animal herbivores do (though I've got friends from Texas who claim that there is a Texan tree that will move from one side of your yard to the other if it is pleased to do so). Generally speaking, a plant can not avoid being consumed by the herbivores by running away. So, it must have a defensive strategy or two that work in situ, and most likely these strategies evolved in relation to the also-…
grrlscientist | July 9, 2008tags: researchblogging.org, evolution, flatfish, Amphistium, Heteronectes, transitional fossils, missing link, Matt Friedman
During the development of extant flatfishes, such as this plaice, Pleuronectes platessa, one eye has migrated round the head to lie on the same side as the other. So these fishes have an 'eyed' (up) side and a 'blind' (down) side suitable for their bottom-dwelling lifestyle.
Image: KÃ¥re Telnes.
Flounder, turbot, sole, halibut and plaice (pictured above) are more than just a tasty slab of flesh on your plate. They are flatfishes that spend their adult life lying…
grrlscientist | July 1, 2008tags: natural selection, evolution, Alfred Russel Wallace, Charles Darwin, Darwin Year, Linnean Society of London
Image: Gary Larson.
This morning, I was pleased to hear National Public Radio was celebrating the 150th birthday of Natural Selection, the mechanism whereby evolution occurs.
One hundred and fifty years ago today, two papers were read in front of the Linnean Society of London. One of those papers was written by Alfred Russel Wallace and the other consisted of two excerpts from Charles Darwin's unpublished writings about the origin of species. It turns out that while Wallace…
gregladen | July 1, 2008Natural Selection was proposed jointly by Alfred Russel Wallace and Charles Darwin on this day 150 years ago.
Darwin discovered the principle of Natural Selection, and worked it out, over several decades prior. Meanwhile A.R. Wallace also came up with Natural Selection as the mechanism for what he was seeing in the wild. Some time in June it became known to Darwin that this guy Wallace as about to roll into town and present his theory. By July 1st, a deal was worked out.
They famously decided to present Wallace's essay (without first asking his permission!), along with two unpublished…
gregladen | June 29, 2008 Proto Stephen Jay Gould OMFSM you are not going to believe this. Over at the University of Chicago, someone is making a terrible fool of themselves. It is hard to say if this is Shankar Vedantam, the Washing Post Staff Writer, or Patterson Clark of the Washington Post or someone else.
The title of the piece is "And the evolutionary beat goes on..."
The piece contains a flash multimedia item that shows the face of a lemur evolving, through a series of other primates, into the face of Stpehen Jay Gould, White Anglo Male. Is there a moment in which he resembles an African person? Maybe…
gregladen | June 28, 2008There is new information from an older idea (from about 2000) by Paul Sherman and colleagues. The idea underlying this research is simple: Symptoms of illnesses may be adaptive. Indeed, this may be true to the extent that we should not call certain things illnesses. Like "morning sickness."
Broadly speaking, there are two different kinds of reasons that a woman may experience nausea in association with pregnancy. 1) This pregnancy thing is a complicated mess with all kinds of hormonal (and other) things going on, so you puke; or 2) a woman who is pregnant feels nauseous for good…