Are the “gill slits” of vertebrate embryos a hoax?

June 14, 2012 • 8:59 am

As most of us know (and all of us who have read WEIT), all vertebrate embryos develop “branchial clefts” (also called “pharyngeal arches” or “branchial arches”) at an early stage, and these are almost certainly the vestigial remnants of the clefts of our fishy ancestors, which develop into gills. Those branchial clefts are sometimes called “gill arches,” even in species, like reptiles, bird, and mammals, that never have gills.  In humans, for example, the clefts disappear and transform into other parts of the body, including the jaw, the middle ear, and the larynx.  Here’s a photo from Wikipedia showing them in humans:

And here they are in a cartilaginous “fish,” a skate (yes, some will take issue with that name, but it’s irrelevant for our purposes):

The second photo is taken from a wonderful new post on the weirdly-named website Playing Chess with Pigeons, written by Troy Britain. The post is called “Gill slits by any other name,” and it’s not only an explanation of where these things come from and what they become in vertebrates, but also an eloquent attack on creationist (and intelligent-design) claims that these “gill slits” in non-fishy vertebrates have nothing at all to do with evolution (here’s an example of one such attack on my book).

The creationist/ID attack on “gill slits” in amniotes (basically, mammals, birds, and reptiles) goes as follows (this is from Britain’s post).

  1. Pharyngeal structures of amniote embryos never function as gills and therefore should not be referred to as “gill slits”.
  2.  Whatever resemblance to the gills of aquatic vertebrates the pharyngeal structures of amniotes has, it is superficial.
  3. Seeing the pharyngeal structures of amniote embryos as being gill-like and calling them gill-slits despite their not functioning as gills is “reading evolution into development”.

Britain takes these claims completely apart.  Go read his post: it’s long but really educational and accessible to everyone.  If you want to spend half an hour learning some great evolutionary biology, by all means invest it in reading Britain’s discussion.

Signs that religion is waning among America’s youth

June 14, 2012 • 4:37 am

A new “American values survey” by the Pew Research Center gives some good news about faith: it’s weakening in America’s youth.  (You can get the full report here; the religion and social values analysis begins on p. 67.) 3008 adults were sampled by telephone according to what seems a pretty good protocol.  A quick summary of the data, though, is best seen here, and you can click on the tabs on the right side to divide up the data by sex, race, age, income, and so on.  On the left you can look at the different questions. Three are religious, involving agreement or disagreement with 1) “Prayer is an important part of my daily life”; 2) “All will be called before God on Judgment Day to answer for our sins”; 3) “I never doubt the existence of God.” In all three cases the youngest people show less faith than their elders. though over the last 25 years belief has been pretty static in the older cohorts.

Individuals were divided into five age classes:

  • Millennials: 1981+
  • Gen X: 1965-1980
  • Boomers 1946-1964
  • Silent generation: 1928-1945
  • Greatest generation: born before 1928

The confidence intervals vary, of course, but the survey’s appendix shows that the 95% confidence intervals for these data are probably around plus or minus 2 – 4%.

There’s a report and data from TPM (“Talking points memo“), a political website:

The younger generation is abandoning God in droves.

A new survey by the Pew Research Center finds that belief in the existence of God has dropped 15 points in the last five years among Americans 30 and under.

Pew, which has been studying the trend for 25 years, finds that just 68 percent of millennials in 2012 agree with the statement “I never doubt the existence of God.” That’s down from 76 percent in 2009 and 83 percent in 2007.

Among other generations, belief in God is high and has seen few changes in recent decades. Between 81 and 89 percent of older generations say they never doubt the existence of God, although the older the generation, the more likely they are to believe in God.

The chart below reflects the Pew survey’s latest findings.

The results suggest that a new movement of atheist or agnostic thinking during the the last decade — spearheaded by high-profile authors like Richard Dawkins, Christopher Hitchens and Sam Harris — is steering younger people away from traditional beliefs long held by their parents.

The trend was also reflected in declining numbers of millennials who agreed with the statements “Prayer is an important part of my daily life” and “We all will be called before God at the Judgment Day to answer for our sins.” Answers to those questions also didn’t change much among older generations.


The TPM plot is better than the Pew Plot as it expands the scale.  The results show this year’s survey compared to earlier surveys:

Here’s the Pew plot for the importance of prayer (note: the colors differ from those used in the TMP plot, so check the key).  Again, there’s stasis in the older generations but a drop in faith (granted, less pronounced than seen above) among “millennials.”

And the plot for the judgment day question, showing the same trend.

Pew summarizes the data for the “God” question (and the two others) as follows:

As a result, the gap between the oldest Americans—the Silent generation – and the youngest, which was just six points in 2007, has increased to 21 points today (89% of Silent generation vs. 68% of Millennials) There have been smaller declines in the percentages of Millennials agreeing to the other two statements about core religious beliefs – the personal importance of prayer and belief in a Judgment Day. Still, just 55% of Millennials agree with all three religious values; among older age cohorts, two-thirds or more agree with all three religion statements.

Is this a real trend among young people? I think so, for I’ve always felt that the secularization of America is inevitable, and will follow the pattern of Europe.  These data, though, show that it’s proceeding faster than I envisioned.  But perhaps the young people will become more religious as they age, a trend that’s been seen in some surveys. Nevertheless, I think this is cause for a bit of celebration.

Is the trend due to the efforts of the New Atheists, as Pew suggests? We don’t know for sure, of course, but the declines begin around 2007, when The End of Faith, The God Delusion, and God is Not Great had all been published.  Now surely lots of these a-religious youth haven’t read those books, but some have, and at any rate those books have helped promote a climate in which it’s less shameful to be seen as a nonbeliever.  It’s only my guess, but I think those books contributed to the erosion of faith among the young. If true, that in turn shows what most of us feel: it’s far more useful to appeal to young people, who may be on the fence about faith, than to try to convert their already brainwashed elders.

All of us who dislike religion and love evolution should be happy about this trend if it’s real.  For acceptance of evolution will follow unbelief as the night follows day. The only people who will mourn this trend will be those misguided faitheists and accommodationists who have an unshakable belief that religion is somehow good for the masses, even if they don’t buy it themselves. Expect to see some blog posts taking issue with the Pew Survey.

There’s a long way to go, of course: nearly 70% of “millennials” still say that they never doubt the existence of God.

h/t: JJE

Fruit fly embryo development visualized in real time

June 13, 2012 • 11:07 am

From Nature News we have this amazing video, “Fruitfly development, cell by cell.” It’s based on two new papers (references below) that produce a three-dimensional image of animal development:

Current light-sheet microscopy techniques involve illuminating one side of the sample. Either one side of a developing organism is imaged continuously, or two sides are viewed alternately, with the resultant data reconstructed to form a three-dimensional view. However, viewing from one side at a time means that the cells cannot be tracked as they migrate from top to bottom, and rotating the sample to view both sides takes so much time that when the next image is taken the cells have changed, so that they no longer line up.

Simultaneous multi-view imaging solves this problem by taking images from opposing directions at the same time and piecing data together in real time. This required massive computing power; the data sets were as large as 11 terabytes (the amount of data on about 2500 DVDs) in one of the studies1. Now every cell in a D. melanogaster embryo can be visualized as the animal develops from a fertilized egg into hatching larva. . .

Keller says that the techniques allow researchers to see what is happening in an entire animal through every stage of development, and what goes wrong as a result of different mutations. “Until now, developmental biology was a qualitative field, describing different mutations and their effect during development. But we couldn’t see what individual cells were doing in an individual embryo,” he says. Keller and his colleagues are now using the technique to follow the growth and differentiation of neurons in the developing brain of D.melanogaster and other species.

Below is the development of a Drosophila melanogaster embryo within the egg. You can see the classic insect segmentation form as the cells move about.  After about a day, this egg will hatch into a larva (the “maggot”), which after about five more days will crawl out of its food (they’re reared in vials of agar-based medium), pupate on the wall of the vial, and then begin the transformation into an adult fly. At 25 degrees C (about 78F), it takes about 8-10 days from when a fly lays an egg until that egg becomes an adult fly (and another 12 hours or so before the adult female can lay another egg), so one can go through 30 or more generations per year. That’s why flies are so good for genetic and evolutionary work.

_______________

Tomer, R., Khairy, K., Amat, F. & Keller, P. Nature Methods http://dx.doi.org/10.1038/nmeth.2062 (2012).

Krzic, U., Gunthur, S., Saunders, T. E., Streichan, S. J. & Hufnagel, L. Nature Methods http://dx.doi.org/10.1038/nmeth.2064 (2012).

Robert Wright blames creationism on atheists

June 13, 2012 • 5:32 am

One can always count on Robert Wright, a nonbeliever, to defend religion and exculpate it from any evils in the world.  Suicide bombers? Mere politics and dispossession. Major Nidal Hassan’s murder spree in Texas? An unfortunate byproduct of America’s own war on terrorism (see Christopher Hitchens’s take on that piece). As Hitchens said, Wright “is now emerging as the leading liberal apologist for the faith-based.”

He does it again in this week’s Atlantic, this time about America’s non-acceptance of evolution. In his piece, “Creationists vs. evolutonists: an American story,” Wright bemoans our failure to embrace Darwin and blames—guess who? Not the religious people who reject the theory of evolution because it violates their beliefs, their scripture, or simply roils their gut. No, he blame (as the Brits say, “wait for it”)—the New Atheists.

Here are the data confronting Wright, from a Gallup poll I’ve written about before:

What we see is pretty much stasis for young-earth creationism (YEC; top line) and theistic evolution (God-guided change; middle line), with a 6% increase in YEC in the last year matched by a 6% decrease in theistic evolutionists. There appears, however, to be a slow, long-term increase in the acceptance of naturalistic evolution (bottom line; see my post on this here), though it’s been very slow.  But Wright concentrates on that 6% increase in YEC, and proffers a theory:

My theory is highly conjectural, but here goes:

A few decades ago, Darwinians and creationists had a de facto nonaggression pact: Creationists would let Darwinians reign in biology class, and otherwise Darwinians would leave creationists alone. The deal worked. I went to a public high school in a pretty religious part of the country–south-central Texas–and I don’t remember anyone complaining about sophomores being taught natural selection. It just wasn’t an issue.

A few years ago, such biologists as Richard Dawkins and PZ Myers started violating the nonaggression pact. [Which isn’t to say the violation was wholly unprovoked; see my update below.] I don’t just mean they professed atheism–many Darwinians had long done that; I mean they started proselytizing, ridiculing the faithful, and talking as if religion was an inherently pernicious thing. They not only highlighted the previously subdued tension between Darwinism and creationism but depicted Darwinism as the enemy of religion more broadly.

If the only thing this Darwinian assault did was amp up resistance to teaching evolution in public schools, the damage, though regrettable, would be limited. My fear is that the damage is broader–that fundamentalist Christians, upon being maligned by know-it-all Darwinians, are starting to see secular scientists more broadly as the enemy; Darwinians, climate scientists, and stem cell researchers start to seem like a single, menacing blur.

I’m not saying that the new, militant Darwinian atheists are the only cause of what is called (with perhaps some hyperbole) “science denialism.” But I do think that if somebody wants to convince a fundamentalist Christian that climate scientists aren’t to be trusted, the Christian’s prior association of scientists like Dawkins with evil makes that job easier. . .

. . . Meanwhile, some data to keep your eye on: Check out the extreme right of the graph above. Over the past two years, the portion of respondents who don’t believe in evolution has grown by six percentage points. Where did those people come from? The graph suggests they’re people who had previously believed in an evolution guided by God–a group whose size dropped by a corresponding six percentage points. It’s as if people who had previously seen evolution and religion as compatible were told by the new militant Darwinians, “No, you must choose: Which is it, evolution or religion?”–and pretty much all of them chose religion.

This is madness. First of all, the data on YEC and theistic evolutionism have fluctuated over the years:  although its adherents were 46% this year and 40% last year, they were 47% in 1993 and 2000.  There is no evidence that an uptick like this is sociologically meaningful, and I’m not even sure whether it differs significantly (in a statistical sense) from the previous survey’s 40%.  And acceptance of straight naturalistic evolution has risen 6% since 2000.  Why does Wright pay attention to a single year’s results and not address the long-term pattern, which is stasis with a slight increase in the good stuff?

What is more maddening is Wright’s blaming this uptick on the New Atheists.  If that were true we’d see an upturn in YEC, and a downturn in theistic evolution, beginning well before this year.  P. Z. has been writing Pharyngula for almost a decade (according to Wikipedia, its inception was on June 19, 2002).  And both Sam Harris and Hitchens have supported evolution against creationism in their own books; Dawkins isn’t the only one who should be blamed. But when were their “big” books published? 2004, 2007, and 2006 respectively.  Why, then, did the uptick occur only this year? Was there such a delayed reaction in the faithful getting the message?

And the dumbest thing of all is Wright’s statement that “A few decades ago, Darwinians and creationists had a de facto nonaggression pact: Creationists would let Darwinians reign in biology class, and otherwise Darwinians would leave creationists alone.”  Is Wright unaware of the many court cases in which creationists didn’t let Darwinians reign in biology class?  The National Center for Science Education lists ten major court cases in which creationists tried to insinuate their filthy camel noses into the public-school tent. All of those took place between 1968 and 2005.  And there was a major revision of textbooks in the 1960s (the BSCS series; see Joseph McInerney’s comment on this below), which was motivated in part by the disappearance of material on evolution from public school texts.  I barely learned about it in high school, and that was in the late 60s.  Some truce!

As always on this topic, Wright is talking out of his nether parts. Every bit of evidence we have suggests that the flatlining of evolution-acceptance in the U.S. is due to the entrenchment of religion in our country. And I’ll point out again that there is not a bit of convincing evidence that atheist biologists have turned Americans away from evolution and toward creationism.  In contrast to the many people who have claimed that Dawkins, for instance, has actually turned them on to evolution as well as helping them purge their religious belief (see his Converts’ Corner), we have almost no people saying that they once accepted evolution but reverted to straight creationism because they couldn’t stomach Dawkins’s atheism. And there’s the palpable failure of the BioLogos Foundation  to get evangelical Christians to accept evolution by trying to show that it comports with their faith.

The reason people choose religion over evolution is not because New Atheists tell them they have to make that choice. It’s because their faith tells them they have to make that choice.

h/t: Dom

Kitteh contest: Jesse

June 13, 2012 • 4:13 am

Reader Jim Billie has sent a picture and story of his late cat Jesse, now with Ceiling Cat:

This is my (late) cat Jesse.  He was rejected by several previous owners; some thought he was stupid.  He was the most intelligent cat I’ve ever known.  He could figure out any door-latch in the world.  He liked to flush the toilet and watch the water swirl.  He was stout:  His weight varied between 18 and 21 pounds.  This earned him the nicknames:  Blobbo and Toilet Seat Cover.  He was sweet and affectionate.  He loved to sleep in my lap as I read and sipped wine.  (I would have him on my lap and my other kitteh on my legs.)  My (dog-loving, cat-disliking) friends liked him and called him “dog-like” (a great compliment from them) due to his affectionate nature.  He possessed all his claws but used them very judiciously.  He was special to me because, in addition to all his other merits, he was the first pet I had as an adult and he worked his way into my heart deeper than any other.  He was a true friend and I was crushed when he passed.  I kept him going for 3+ years with daily insulin shots (and more heroic measures towards the end) before kidney failure took him at age 15.  I buried him in my backyard myself, along with a can of tuna:  His favorite food.  (Funny how silly superstitious stuff like that still feels right sometimes!)

I will still accept cat pictures and stories, though there is a queue (note: cats aren’t posted in order of receipt, but according to my whim).

Hitch redux

June 12, 2012 • 11:44 am

Here are two pictures of Hitchens that someone sent me.  He’s clearly already undergone cancer treatment, but I like these because they show him doing what he loved to do, right up to the end: writing and being among his books.

You can see more photos here, all taken by the Washington photographer Brooks Kraft). Have a look at the closeup of his writing table at Brooks Kraft’s site; it shows the “Queasy Pops” he was sucking to reduce the nausea produced by chemotherapy. Click both pictures to enlarge them.