I am jumping on a meme bandwagon: Seven Quick Takes Friday, hosted by Jen F. at Conversion Diary. Since this is a blog about science and faith, not a personal diary, I hope Jen will forgive me if my seven snippets consist of news, info, and thoughts about those subjects.

1.

If you grow your young in a uterus, but you have not evolved a placenta, how do you feed them? For the gray nurse shark, aka the sand tiger shark, the answer is incestuous cannibalism. Gray nurse shark pups in the womb eat each other for nourishment, so only two are born per pregnancy (females have two uteruses). Since they are endangered, marine biologist Nick Otway is trying to develop an artificial uterus for gray nurse shark pups. Back when I worked as an aquarium biologist, we had several of these huge sharks. They are quite docile despite their fearsome complement of teeth.

At right: Grey nurse shark at the Minnesota Zoo, courtesy Joe Lencioni. (CC) Some rights reserved.

2.

Check out this video of comedian Stephen Crowder, hosted by the Raving Theist (formerly the Raving Atheist). He does an over-the-top parody comparing Planned Parenthood to a used car salesman.

3.

From the world of physics (via Scientific American) comes a story about the continued dissonance between Einstein's special relativity and quantum mechanics. This particular story has to do with a principle of special relativity called locality, which conflicts with a principle of quantum mechanics called entanglement. Of note is a comment buried on page 4 of the online article:

The old aspirations of physics to be a guide to metaphysics, to tell us literally and straightforwardly how the world actually is—aspirations that had lain dormant and neglected for more than 50 years—began, slowly, to reawaken.

This is good news for philosophers who, like me*, view reality as a concrete thing and truth as absolute.

*Not that I am any kind of philosopher.

4.

Shame on the New York Times for its headline, "For Catholics, a Door to Absolution is Reopened." The article is about the church's promotion of indulgences — which are decidedly not the same as absolution, and which have never had the door closed, having always been available. The Times notes that the tradition of indulgences is "one of the most complicated to explain," then proceeds to do a rotten job of explaining it. In particular is the omission of the crucial point that Purgatory is a process of purification, of making us more like God so we can enter his heaven, not a place in space-time where one serves a sentence of days or years. (Hat tip to Science and Religion News.)

5.

When Pluto was removed from the list of planets, it became the first discovered member in a brand-new class of space objects: the dwarf planets. In a way, this is actually a promotion, not a demotion. But apparently a lot of people are emotionally attached to Pluto as a planet. In 2007, the State of New Mexico (home of Pluto's discoverer, Clyde Tombaugh) declared Pluto officially a planet. (Hat tip to Spaceports blog.) This reminds me of the apocryphal tale of one of the Appalachian states (Tennessee?) trying to declare the mathematical constant pi as equal to exactly 3.

At right: Image of Pluto and its moons by the Hubble Space Telescope (courtesy of NASA).

6.

If you are Catholic, and the Pope himself told you to your face that you were wrong on some issue, would you reconsider your position? Apparently, Nancy Pelosi would not. She shows no signs of easing from her pro-choice stance despite a face-to-face reprimand from Pope Benedict XVI. One prays that at least a seed was planted.

7.

Until now, the Alavesia fly was an insect known only from amber fossils from the Cretaceous period, before the mass extinction that killed the dinosaurs and many other species. Now two species of living Alavesia have been found in Namibia and have been dubbed "living fossils" by the media. A completely new suborder of insects, the Mantophasmatodea, was discovered as well. There is still much we do not know about the mysterious world of living things. It's no surprise the new discoveries were insects; there are an estimated six to ten million species of insects, but only about a million have been described.

This post is a contribution to the blog swarm "Blog for Darwin," held from February 12-15, 2009, to celebrate the 200th anniversary of Charles Darwin's birth.

When Charles Darwin published On the Origin of Species in 1859, introducing the world to the revolutionary concept of evolution through natural selection, he noted that "perhaps ... the most obvious and gravest objection which can be urged against my theory" was the apparent lack of "transitional" fossils in the geological record. He speculated that the reason that "geology ... does not reveal [a] finely graded organic chain" of intermediate forms was because of the paucity of fossil discoveries at the time.

In one sense, every species that has ever existed is a "transitional" form; it reflects characteristics of its ancestors, and its characteristics will be reflected in its descendants. But humans are impressed by the dramatic, and in the years since Darwin's first book on evolution was published, some very dramatic fossils, intermediate between two large classes, have been discovered.

The most famous of these is Archaeopterix, which depending on one's interpretation is either a a bird with teeth and clawed hands or a feathered, flying dinosaur. But another lesser-known fossil is equally dramatic as an example of a transitional form: the marvelous Ichthyostega.

Ichthyostega is an intermediate form between fishes and amphibians from the late Devonian period, about 365 million years ago. One could describe it as a fish with legs that could walk around on land, or one could say it was an amphibian with the head and tail of a fish. Since fish have their weight supported by the water, Ichthyostega faced the problem of supporting its weight on land, which was accomplished by thickened, overlapping ribs — a clumsy, primitive solution necessary because it had so recently evolved from its lungfish-like ancestors.

Ichthyostega had seven toes on each hind foot, notable since the number of toes on tetrapod* feet stabilized at five early in their evolution. Its shoulder and hip had adaptations to help it move about on land. Its hind limbs could support its body as a juvenile, but were likely too weak to support its full weight on land in adulthood. It is hypothesized that juveniles could leave the water to escape predators, but adults only partially pulled themselves out of the water to sun themselves.

Ichthyostega is one of many fossils that fill in the natural history of the evolution of tetrapods from fish. The story is still not complete: "Romer's gap" (named after paleontologist Alfred Sherwood Romer) is a 20 million year period of missing fossils between Ichthyostega and its contemporaries and the next-oldest known tetrapods.

Gaps in the fossil record like this were a worry to Darwin, who recognized them as a potential rebuttal of his seminal theory. Yet absence of evidence is not evidence of absence; the most parsimonious explanation for Romer's gap remains the one Darwin put forth — the incompleteness of the geological record. Charles Darwin's extraordinary theory is now secure as one of the most well-established, concrete principles of biology.

*Tetrapods are four-legged vertebrates and their descendants; in other words, all vertebrates except fish.

More information on Ichthyostega

• Ichthyostega from the Tree of Life web project
• Cladogram showing Ichthyostega's place in the evolution of tetrapods (Palaeos database)

Ichthyostega image information

• Top right: Reconstruction of a juvenile Ichthyostega from the National Museum of Natural Science in Taiwan. Photo by Alton Thompson. (CC) Some rights reserved.
• Left: Pencil drawing of Ichthyostega. From Wikimedia Commons, licensed under the GNU Free Documentation License (GFDL).
• Bottom right: Drawing of Ichthyostega skeleton. The forelimbs are incompletely fossilized and the hand morphology is unknown. From the Tree of Life web project (link above), after Ahlberg et al. 2005. (CC) Some rights reserved.