How an embryo is like a meatball sub

I’ve only just noticed that I have a fondness for food metaphors when talking about development — gastrulation is a peculiar way to make a jelly sandwich, neurulation is like rolling up a burrito, and somite formation is a meatball sub. They sort of illustrate the arrangement of the tissues involved, but of course they all have shortcomings…but then explaining how the metaphor doesn’t work can be just as informative as the metaphor itself.

For instance, early in its development, the vertebrate embryo consists of two epithelial sheets, the epiblast and hypoblast, pressed against each other like two slices of bread. That’s easy to visualize. It also allows me to explain the core idea of an epithelium — a layer of cells tightly linked to one another to form a continuous more or less two dimensional sheet. A lot of animal development is about epithelia folding and contacting other layers. But another important concept is that some cells are not in sheets — they’ve dissociated and are moving in a loose mass surrounded by an extracellular matrix. This is called mesenchyme. Mesenchyme would be the gooey jelly between the two sheet-like bread slices.

[Read more…]

Besides, the United Federation of Planets is clearly socialist

Ted Cruz tried to claim Captain James T. Kirk for the Republican party. This is illogical and must be refuted.

I offer two pieces of evidence.

  • William Shatner’s own words.

    Star Trek wasn’t political. I’m not political; I can’t even vote in the US. So to put a geocentric label on interstellar characters is silly

  • Does this sound like a Republican to you?

Case closed.

Bad science books still get published


Wasn’t it enough that I read Nessa Carey’s terrible Junk DNA book? It scarred me, it did. But there’s another one out, John Parrington’s The Deeper Genome: Why there is more to the human genome than meets the eye, and no, I REFUSE TO READ IT. I have been reading Larry Moran’s multi-part evisceration of Parrington, though. It’s spectacularly gory. There are bits of Oxford lecturer in pharmacology spattered all over the place.

[Read more…]

Now what?


NASA has announced the discovery of a distant earth-like planet, Kepler-452b.

Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.

While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star Kepler-452 than Earth is from the Sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.

“We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment,” said Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. “It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

[Read more…]

Answers in Genesis explains “Were you there?”


One of the common tactics of believers in Young Earth Creationism, and devotees of Answers in Genesis, is to reply to statements about evolution with the question, “Were you there?” Ken Ham has been pushing this approach since at least 1989, and it’s dishonest horseshit, as I’ve explained at length.

It really is a stupid question, but now my eyes have been opened, as Roger Patterson of AiG explains exactly what the question is intended to do.

[Read more…]