evolution
evolvingthoughts | December 25, 2006
Larry Moran, at Sandwalk, has argued that evolution is indeed a matter of chance. It is, he thinks, something that atheism requires. This is an interesting issue, one that has deep roots, both in the role of chance explanations in science and prescience, and the theistic reaction to it.
Larry says
It's perfectly okay to say, as a first approximation, that lots of evolution is random or accidental. This is a far closer approximation to the truth than saying it's the all the result of design by natural selection.
What role does randomness or accident play here? Is it an explanation to…
evolgen | December 25, 2006Carl Zimmer has an article in the upcoming edition of Scientific American that looks at cancer from the perspective of evolutionary biology. The most obvious parallel is that of cancer cells within an individual modeled as an evolving population:
Rare mutations, for instance, may cause a cell to lose restraint and begin to multiply uncontrollably. Other mutations can add to the problem: They may allow deranged cells to invade surrounding tissues and spread through the body. Or they may allow tumor cells to evade the immune system or attract blood vessels that can supply fresh oxygen.
Cancer,…
evolvingthoughts | December 24, 2006
It's a season, so I am told, that has something to do with religion. We celebrate the birth of commodity capitalism, or something. So I thought I would combine my favourite issues - philosophy, religion and evolution.
It's all Alex Rosenberg's fault. At a dinner before the conference, he was sitting opposite me, and talk turned, as it does, to creationist attacks on science. Alex made the following claim: It is not possible to be a theist and believe in evolution by natural selection consistently.
I demurred, of course. But on further thought, I wondered if he might not be right.
To…
jlynch | December 23, 2006
Over at Pharyngula, PZ has a nice story about how the Doushantuo fossils (example on right), thought to be cleavage-stage animal embryos from 580 mybp, may in fact be fossilized bacteria (example on left). Check it out.
clock | December 23, 2006The Icons of Evolution finally tested! Who won? Lamarck or Darwin?
Under the fold:
Winning By A Neck: Giraffes Avoid Competing With Shorter Browsers:
The giraffe's elongated neck has long been used in textbooks as an illustration of evolution by natural selection, but this common example has received very little experimental attention. In the January issue of the American Naturalist, researchers at the Mammal Research Institute in the Department of Zoology and Entomology at the University of Pretoria tested whether foraging competition with shorter herbivores could explain why giraffes…
pharyngula | December 23, 2006Almost ten years ago, there was a spectacular fossil discovery in China: microfossils, tiny organisms preserved by phosphatization, that revealed amazing levels of fine detail. These specimens were identified as early animal embryos on the basis of a number of properties.
The cells were dimpled and shaped by adjoining cells, suggesting a flexible membrane—not a cell wall. This rules out algae, fungi, and plants.
The number of cells within each specimen was usually a power of 2. This is something we typically see in cleaving embryos, the sequence from 1 to 2 to 4 to 8 to 16 cells.
They were…
evolvingthoughts | December 22, 2006
My mate Marc Buhler noticed this one:
This week's issue of Science magazine has an article that is the subject of a story (pasted below the fold) from the NY Times.
"From Scum, Perhaps the Tiniest Form of Life" by William J. Broad - Dec. 23, 2006
The smallest form of life known to science just got smaller.
Four million of a newly discovered microbe - assuming the discovery, reported yesterday in the journal Science, is confirmed - could fit into the period at the end of this sentence.
Scientists found the microbes living in a remarkably inhospitable environment, drainage water as…
evolgen | December 22, 2006Via the error prone cosmologists I learned about this challenge:
Physicist Richard Feynman once said that if all knowledge about physics was about to expire the one sentence he would tell the future is that "Everything is made of atoms". What one sentence would you tell the future about your own area, whether it's entrepreneurship, hedge funds, venture capital, or something else?
We evolutionary biology bloggers are a bit ahead of the game on this one, presenting our definition of evolution in 10 words or less:
Differential inheritance of genetic variation via stochastic and deterministic…
jlynch | December 21, 2006While some may be blogging about large extinct beasties, it's also worth remember the little ones. AP is reporting:
The discovery of fossilized remains of a mouse-like animal that lived at least 16 million years ago is the first hard evidence that New Zealand had its own indigenous land mammals, a researcher said Thursday.
New Zealand paleontologist Trevor Worthy and his team say they discovered two parts of a jaw and a femur (thighbone) -- about the size of a fingernail -- during digs in New Zealand's Central Otago region from 2002 until 2004. Their findings were published in the…
pharyngula | December 21, 2006
What are the key ingredients for making a multicellular animal, or metazoan? A couple of the fundamental elements are:
A mechanism to allow informative interactions between cells. You don't want all the cells to be the same, you want them to communicate with one another and set up different fates. This is a process called cell signaling and the underlying process of turning a signal into a different pattern of gene or metabolic activity is called signal transduction.
Patterns of differing cell adhesion. But of course! The cells of your multicellular animal better stick together, or the…
clock | December 21, 2006The eighth part of my lecture notes series. As always, please pitch in and make my lectures better by pointing out the factual errors or making suggestions for improvement (originally posted on May 17, 2006):
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Evolution
BIO101 - Bora Zivkovic - Lecture 2 - Part 4
Imagine a small meadow. And imagine in that meadow ten insects. Also imagine that the ten insects are quite large and that the meadow has only so much flowers, food and space to sustain these ten individuals and not any more. Also imagine that the genomes of those ten…
jlynch | December 20, 2006
Regular readers may remember that I have a softspot for catfish and earlier this year purchased a lace catfish (Synodontis nigrita), a species native to many African countries. The genus Synodontis (Cuvier 1816) is interesting for a number
of reasons. For example, S. multipunctatus (the gorgeous fish pictured above) is the only fish known to practice brood parasitism: it manages to mix it eggs with those of mouthbrooding cichlids in Lake Tanganyika, its larvae grow faster than those of the host and feed on them.
Lake Tanganyika is, of course, famous for the cichlids which have been studied…
jlynch | December 19, 2006
A malformed embryonic or neonate choristoderan reptile from the Lower Cretaceous Yixian Formation of northeastern China is described. The tiny skeleton exhibits two heads and two necks, with bifurcation at the level of the pectoral girdle. In a fossil, this is the first occurrence of the malformation known as axial bifurcation, which is well known in living reptiles.
Buffetaut et al. (2006) "A two-headed reptile from the Cretaceous of China" Biology Letters Early Online (DOI: 10.1098/rsbl.2006.0580)
jlynch | December 19, 2006From EurekaAlert:
Approximately 6 percent of human and chimp genes are unique to those species, report scientists from Indiana University Bloomington and three other institutions. The new estimate, reported in the inaugural issue of Public Library of Science ONE (Dec. 2006), takes into account something other measures of genetic difference do not -- the genes that aren't there.
That isn't to say the commonly reported 1.5 percent nucleotide-by-nucleotide difference between humans and chimps is wrong, said IUB computational biologist Matthew Hahn, who led the research. IUB postdoctoral…
pharyngula | December 19, 2006Once upon a time, in Paris in 1830, Etienne Geoffroy St. Hilaire debated Georges Léopole Chrétien Frédéric Dagobert,
Baron Cuvier on the subject of the unity of organismal form. Geoffroy favored the idea of a deep homology, that all animals shared a common archetype: invertebrates with their ventral nerve cord and dorsal hearts were inverted vertebrates, which have a dorsal nerve cord and ventral hearts, and that both were built around or within an idealized vertebra. While a thought-provoking idea, Geoffroy lacked the substantial evidence to make a persuasive case—he had to rely on fairly…
evolgen | December 19, 2006
Via this press release I learned about this book: The Top Ten Myths About Evolution. The book deconstructs ten myths that creationists propagate while spreading misinformation. It also gives me an excuse to post cute pictures of furry primates.
The official website lists the ten myths:
1) Survival of the Fittest; 2) It's Just a Theory; 3) The Ladder of Progress; 4) The Missing Link; 5) Evolution is Random; 6) People Come from Monkeys; 7) Nature's Perfect Balance; 8) Creationism Disproves Evolution; 9) Intelligent Design is Science; 10) Evolution is Immoral
It sounds like a good treatment of…
razib | December 19, 2006Check out the list (upon which a book is based). Food for thought, some of the "myths" are actually starting points for philosophical debates (e.g., Dawkins vs. Gould).
oracknows | December 19, 2006
Here's a great idea:
I was staying in a hotel in New York earlier this year, and I noticed that as well as the usual Gideon's bible, there was also a copy of the Quran. So that got me thinking - why limit the principle to religious books, why not get some science in there too?
So, I've decided that from now on, whenever I stay in a hotel room, I'm going to leave behind a copy of ... The Origin of Species...
And now ... I'd like to call on everyone who reads this to do the same thing - next time you stay in a hotel, leave behind a copy of this seminal work. After all - what's the cost of one…
razib | December 18, 2006The whole post is worth reading, but the money shot:
The central point of the paper is exceedingly simple. Haldane demostrated in 1927 that the fixation probability of a single copy of a new adaptive allele is 2s. This means that if archaic humans had any alleles that would have been adaptive for modern humans, it would take only a very small amount of interbreeding for modern humans to pick up these alleles, with a near-100 percent likelihood.
Greg Cochran has more. Obviously this work builds upon the Lahn introgression paper. Instead of crude species typologies the data is now pointing to…