evolution
mikethemadbiologist | June 18, 2006In what I think is the only way to
cope with the Blond Banshee (aka the Coultergeist), PZ writes (italics mine):
Like I said, I'm not going to take this trip apart sentence by sentence, even though I could, given enough time and interest. I will suggest instead that if anyone reading this thinks some particular paragraph anywhere in chapters 8-11 is at all competent or accurate in its description of science, send it to me. I couldn't find one. That's where the obligation lies: show me one supportable claim in Coulter's farrago of lies and misleading statements and out-of-context quotes, and…
clock | June 17, 2006On June 17th, 1858 (I know, I missed by less than an hour), Charles Darwin received a letter from Alfred Russel Wallace. The letter contained the explanation of the principle of natural selection. Thus, Darwin was forced to act, and act fast. After reading both Wallace's and his own acccount of natural selection to the Royal Society, he got down to work. Instead of a multi-tome monograph he was planning on writing (which, if nothing else due its sheer size, would not have had quite as wide readership), he quickly jotted down a slim volume which, for the Victorian era, was a surprisingly…
mikethemadbiologist | June 17, 2006I go for a walk, and watch some soccer, only to find out that Thursday, the South Carolina Education Oversight Committee passed 'standards' that force students to "summarize ways that scientists use data from a variety of sources to investigate and critically analyze aspects of evolutionary theory." I have to hand it to the creationists: pushing this during the summer, when university faculties are off doing science, is probably the right time to do something like this. Too bad it will make the kids of South Carolina ignorant and stupid. Teaching the basics of evolutionary biology is hard…
loom | June 17, 2006Two hundred thousand years ago or thereabouts, an African lion killed someone. Along with a meal, the big cat got a wicked stomachache. Today a record of that unfortunate death still survives, in the bacteria that make big cats sick.
The trail of this strange story starts in the 1980s, when scientists discovered that ulcers are caused by bacteria known as known as Helicobacter pylori. H. pylori is found in people around the world, and scientists learned how to recognize the different strains they carried. Based on the patterns of the strains, a team of scientists concluded in 2003 that…
evolvingthoughts | June 17, 2006
The cluster of genomes of asexual organisms forms what is called a "phylotype" (Denniston 1974, a term coined by C. W. Cotterman in unpublished notes dated 1960; I like to track these things down). Phylotype is a taxon-neutral term, though, that is determined entirely by the arbitrary level of genetic identity chosen. For example, "species" in asexuals might be specified as being 98%+ similarity of genome, or it might be 99.9%+ (I have seen both in the literature). A phylotype of, say 67% or 80% might be used for other purposes (such as identifying a disease-causing group of microbes).
The…
evolvingthoughts | June 16, 2006
Reposted from the old blog.
OK, this is one of a series of posts in which I will play with ideas that might will become a paper.
The problem is this: usually we define a species as a group of related organisms that share genes (or a gene pool, which amounts to the same thing). Sometimes we include also ecological considerations (either in the form of natural selection, or in terms of sharing a niche).
But many microbial species either do not share genes to reproduce, or they can but do not need to. So, the question is sometimes raised whether microbes (of this kind) form species at all…
pharyngula | June 16, 2006
The diagram above shows the early cleavages of the embryo of the scaphopod mollusc, Dentalium. You may notice a few peculiarities: the first cleavage is asymmetric, producing a cell called AB and a larger sister cell, CD. Before the second division, CD makes a large bulge, called a polar lobe, and it almost looks like it's a three-cell stage—this is called a trefoil embryo, and can look a bit like Mickey Mouse. The second division produces an A, a B, a C, and a D cell, and there's that polar lobe, about as large as the regular cells, so that it now resembles a 5-cell embryo. What's going on…
evolvingthoughts | June 16, 2006I recently [some time back now - this being a repost] received this question in email. I hope the correspondent doesn't mind my posting it anonymously.
I notice from www.dictionary.com that the word "Devolution" is a term in biology which means "degeneration". Is it an antonym of the word "Evolution" (which is the most likely reason why creation "scientists" state tiresome statements like "evolution would argue for improvements all the time")? Or does the word "devolution" touch on stuff that may or may not be related to evolutionary biology?
Traditionally, degeneration meant simply change…
razib | June 16, 2006The answers keep coming in for my query about "what is evolution?" RPM took me to task for basically answering "what is selection" with my initial response. This is a good criticism...honestly, I wanted to focus on selection because I think random genetic drift confuses many people, and it quickly turns into a black box incantation that explains everything and nothing. But here's another point of interest: selection is stochastic as well! That is, selection favors fitness, and fitness tends to exhibit particular characteristics in particular environments (e.g., extremely fast vertebrate…
cmooney | June 15, 2006Okay, here's round two of Bethell mania. Once again, I'm going to post several brief excerpts from his arguments (this time on evolution), and let you respond to them--thereby helping me out with my debate prep. You did a stellar job with global warming, so I expect no less this time around!
Here goes:
1. In the evolutionist worldview, life on earth evolved from inanimate matter over a long period as a result of random events. If it really is true that all creatures great and small appeared on earth in this fashion, then we have no reason to believe that life is anything other than a cosmic…
evolvingthoughts | June 15, 2006Razib has proposed an interesting challenge: Define evolution in ten words or less.
His definition is this:
Differential fitness correlated with heritable variation results in evolution
John Hawks' suggestion is this:
No evolution means equal offspring for everyone!
But both of these focus only on the genetic or selective aspect of evolution (including genetic drift under that rubric). There's a lot more happening in evolution that selection and drift. So here's my suggestion:
Diversity changes through time at all levels of biology.
Why do I not focus on heredity, variation, or selection?…
oracknows | June 15, 2006I don't know if it's possible to be to the right of Ann Coulter, but Spacemonkey over at IMAO gives it a try.
I'm not sure that he succeeds. After all, he says, "We let God's will or survival of the fittest, if you swing that way, be the appeals process."
I don't think that Coulter would never concede even in the least that anything even remotely connected with evolution could be true--at least not in public.
evolvingthoughts | June 15, 2006A recent paper in Nature, Speciation by hybridization in Heliconius butterflies is getting a fair bit of comment on the internet. This is a case where the researchers, wondering if an Andean butterfly species was a hybrid of two others, decided to test the hypothesis by re-evolving it deliberately.
The process is called "homoploid" because there was no change in chromosome number. Previous studies in various organisms, particularly in plants, but not restricted to them, had shown cases of speciation by hybridisation where disparate numbers of chromosomes in the hybrid were equalised by a…
clock | June 15, 2006A lot of interesting posts appeared over the past day or two concerning evolutionary theory, what evolution is and how it works.
It all started with Jonah Lehrer's article in SEED Magazine on the ideas of Joan Roughgarden:The Gay Animal Kingdom to which PZ Myers responded with Evolution and homosexuality and Jonah responded with agreement: PZ vs. Roughgarden.
I responded with a post in which I linked to my old review, Books: 'Evolution's Rainbow' by Joan Roughgarden, and ended with a minor quip that switched the discussion from homosexuality to the question of units of selection: Sexual…
loom | June 15, 2006A bunch of good reviews on natural selection in humans are coming out, reflecting the explosion of research on how evolution has shaped our genome. See here and here. Today in Science another good one is out. What sets this one apart from the others is that it comes with a slide show with audio from the authors. As far as I can tell, the show is free. And it's a pretty clear summary. Check it out.
jrosenhouse | June 15, 2006MSNBC is reporting the discovery of yet another transitional form, this time linking ancient and modern birds:
Dozens of fossils of an ancient loonlike creature that some say is the missing link in bird evolution have been discovered in northwest China.
The remains of 40 of the nearly modern amphibious birds, so well-preserved that some even have their feathers, were found in Gansu province, researchers report in Friday's issue of the journal Science. Previously only a single leg of the creature, known as Gansus yumenensis, had been found.
“Gansus is a missing link in bird evolution,” said…
evolgen | June 15, 2006What is evolution? Razib started it. John Hawks joined in. I offered my opinion in the comments on GNXP. But I felt obliged to say more, here.
It seems like most of the readers in the ScienceBlogs universe don't understand the difference between evolution and natural selection. When Razib asked them to provide the thing they would want the public to understand about evolution (in ten words or less, mind you), most of them provided explanations of natural selection. Let me say it as clearly as I possibly can, evolution is more than natural selection.
I am not a neutralist. Check out the…
clock | June 15, 2006The Aquatic Ape theory is bunk, but Aquatic Sparrow theory just got a huge boost. There is no way I can explain the Big Evolution News Of The Day as well as Grrrlscientist did, so please go here and enjoy the amazing news of the wading/aquatic ancestors of all modern birds, with the beuatiful pictures of excuisitely well-preserved fossils from China.
grrlscientist | June 15, 2006
Artist's rendition of Gansus yumenensis
on a lake in Changma Basin, China approximately 115-110 million years ago.
Illustration: Mark A. Klingler / CMNH.
In 1984, a paper was published in China (in Chinese) that described a new bird species from the early Cretaceous period, based on part of a fossilized left foot bone that had been discovered in northwestern China by a team of paleoichthyologists in 1981. This bone was determined to be part of an ancient tern-sized bird, later named Gansus yumenensis (for the Chinese province of Gansu, and Yumen, the nearest somewhat large town to where…
razib | June 15, 2006Bora's reference to popular misconceptions about evolution and RPM's post which points to some of Francis Collins' bizarre contentions in regards to human evolution (talk about "End of History") got me thinking, how about I be a unifier and not a divider? If you had 10 words or less, what would you have the public master (and I mean internalize, not spit back as a creed) about evolutionary theory?
Here is my shot:
Differential fitness correlated with heritable variation results in evolution
This an attempt to condense Richard Lewontin's "three conditions" for biological evolution:
(i) there…