Thursday, July 15, 2010

Chicken vs. Egg


Above: Whichever came first, they're equally delicious. Egg photo by Fir0002/Flagstaffotos, licensed. Chicken photo by 3268zauber, licensed.

Today I read possibly one of the dumbest science news articles of all time, or at least the most condescending. Somewhere in here is news of an interesting study. English scientists have isolated the protein responsible for the formation of hard-shelled eggs in chickens, a step forward in developmental science that could potentially yield applications for materials science. So, how to make sure this mildly interesting study grabs the attention of Joe Six-pack? Put out a press release to every major media outlet claiming to have solved the "age old problem" (really?) of which came first, the chicken or the egg?

The Chicken and the egg: Ancient mystery solved?

Not only is this silly eyeball-grabbing headline a blatant attempt to pander to the lowest common denominator and point out what a complete joke science reporting has become, it assumes the absolute worst about the reader's level of science comprehension and interest. And it's obviously completely wrong!

The articles in question "argue" that because a protein for forming eggshells is found inside chickens, this proves that the chicken came before the egg.

Not only is this severely flawed logic, you don't need a discovery to prove the answer one way or the other: If you really want an answer to this rhetorical philosophical conundrum, it's obvious using simple logic and knowledge of how evolution works.

Let's define some terms first. I think implicit in this old riddle is the fact that we're talking about chickens Gallus gallus and chicken eggs here, specifically.

Nothing in the report suggests that proteins for hard shells originated with modern chickens. In fact, we know from observation that all other bird species, including those more primitive than chickens, lay hard-shelled eggs (though as PZ Myers points out in the link below, they often use a different protein). We know based on fossil evidence that hard-shelled eggs were laid by not only non-avian theropods but also sauropods and ornithischians. In contrast, softer shelled eggs are found in crocodilians and pterosaurs. So we know that the hard-shelled egg this protein (or the genes coding for it or similar proteins) allows evolved among ornithodirans sometime after pterosaurs diverged but before ornithischian and saurischian dinosaurs split. So, let's ballpark it to the early-mid Triassic period for the appearance of hard-shelled eggs. Even allowing for the broadest possible definition of "chicken" (Galliformes), the earliest you can say chicken-like creatures walked he earth is the late Cretaceous, when the stem-anseriform Vegavis lived (so we know that the chicken line must have split from the duck line by that time).

That covers the hard shelled egg in general, which clearly came long before the chicken. What about modern chickens specifically and their eggs? This gets down to the biological species concept, of which there are many and they all overlap. Is a chicken anything that can successfully breed with any random clucker down at the farm? If so, we're getting into some sticky concepts of ring species and sub-species here, which just muddy the waters, especially when ancestral species are taken into account. Let's just say for our purposes, a "chicken" means the type specimen of Gallus gallus domesticus, and its specific genome. The species this bird belongs to, however you define it, diverged from an ancestral population that we can say was non-chicken. The relevant mutations or changes in allele frequency that define the line between chicken and non-chicken almost certainly did not occur inside the living adult non-chicken and were then passed on to its offspring in some kind of Lamarckian evolutionary event. Rather, they would have taken place in the cell divisions leading to the formation of the first true chicken egg.

Put more simply, a non-chicken did not spontaneously transform into a chicken via some kind of Fantastic Four style cosmic wave, and it did not spring spontaneously with all its essential chickenness in place from the head of Zeus. Rather, a non-chicken had to have laid an egg containing a chicken embryo. Can this be said to be a chicken egg, if it was laid by a non-chicken? I'd day yes, as it contains a chicken. Though ultimately, maybe this classic paradox is better left to philosophers after all.

PZ Myers of Pharyngula has done his own write-up on this travesty of science reporting and goes into more detail on the protein angle, well worth a read here. PZ says that "you simply can't make the conclusion the reporter was making here" but, given the prevalence of this exact conclusion in other articles from other news sources, everybody is simply copying one idiot science writer or, more likely, this conclusion was actively promoted by a press release. I can't decide which would be worse.

EDIT: This is getting hilarious. No, not the plethora of tragically inevitable comments from creationists, but watching the American media slowly realize that every single one of their science writers who allowed this nonsense to be repeated on their pages are being laughed at by people who took middle school biology, even in their own comments. Case in point: A single editor's note has been made on the CNN Article headline: "Maybe." Not, "Sorry, our so-called journalists are too stupid to recognize an obvious load of crap when they see it, or at the very least point out the crap being served to them in press release form. The people responsible have been fired and we're hiring a literate this time."

Just, "Maybe. Maybe not. Reality: you decide!"

*head-desk*

2 comments:

  1. Just a minor nit pick. Crocs have hard shelled eggs too. Though starting the evolution of the hard shelled egg for birds at around the Triassic is still probably valid, as this may have been a convergent evolution (much like the eggs of geckos and turtles).

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