........or is there any taste in the white of an egg? Job 6:6
"Touted as an evolutionary explanation for bird egg shapes, a new hypothesis celebrating natural selection falls like Humpty Dumpty under a gentle breeze of questioning.
Natural selection is the hero of a paper in Science Magazine about bird eggs, and Phys.org was sure to make that clear in its write-up. “How eggs got their shapes: Adaptations for flight may have driven egg-shape variety in birds,” the bold headline announces. Read further in this article classified under evolution, and you see that a Professor of Organismic and Evolutionary Biology from Harvard used an evolutionary framework to determine the “implications of egg shape in an evolutionary and ecological setting.” This egg story is drenched in evolutionary seasoning, to make sure the reader won’t miss the taste.
The selection pressure that best explains its evolution comes from the characteristic we most associate with birds: flight.
This hypothesis predicts that species under strong selection for flight-related adaptations—such as migrants and aerial insectivores—should have elliptical or asymmetric rather than spherical eggs.
The authors use an index of aerodynamic wing shape as a proxy for such selection, and find that this is by far the best predictor of egg shape.
Why, then, are there no hot-air balloon–shaped eggs? Not only do they appear developmentally hard to produce, but perhaps they offer no obvious selective advantage over a spherical egg: They are still inconveniently wide, with little increase in volume.
Egg collecting is now deeply unfashionable and rightly illegal. But from its heyday in the late 19th to the mid-20th century, it has bequeathed to us data that can yield wonderful evolutionary insights, as Stoddard et al.‘s study underlines.
Can the evolutionary answer stand up to a gentle whiff of questioning? A running theme at CEH is
that natural selection is a vacuous concept masquerading as a scientific explanation. By failing to provide real concrete predictions that are testable, natural selection reduces to the Stuff Happens Law—the opposite of explanation. Whatever happens, “it evolved,” so that the explanation becomes a just-so story. Are these scientists and reporters playing make-believe again?
We should note first that egg shapes are examples of microevolution. Getting a chick to develop in 21 days that can hatch and fly is the big issue for evolution; egg shape and size seem very minor by comparison. We might compare the phenomenon to a magician pulling a rabbit out of a hat. Changing the shape of the hat or the size of the rabbit doesn’t matter as much as being able to do the trick itself. Furthermore, the evolutionary story fails to rule out creation or intelligent design, because advocates of those positions are perfectly happy to see variation in egg shape for different species, and are willing to admit some degree of change over time. So far, then, we don’t see the evolutionary story deserving of privileged status.
The biggest piece of evidence they adduce is the chart showing a correlation between flight behavior and egg shape. It’s an interesting pattern. Correlation, however, does not imply causation. Does the egg shape drive the female bird’s oviduct, or does the oviduct drive the egg shape? If aerodynamic efficiency makes natural selection drive egg shape, one would think it would also drive everything else about the bird, like beak shape and mass. But beaks among strong flyers vary all over the map (consider pelicans, hummingbirds, and Arctic terns). Females only lay eggs when they are not flying, furthermore (for good reason), and what about the males, who don’t have an oviduct? It’s not exactly clear why natural selection would have any influence on egg shape." CEH
Natural selection is the hero of a paper in Science Magazine about bird eggs, and Phys.org was sure to make that clear in its write-up. “How eggs got their shapes: Adaptations for flight may have driven egg-shape variety in birds,” the bold headline announces. Read further in this article classified under evolution, and you see that a Professor of Organismic and Evolutionary Biology from Harvard used an evolutionary framework to determine the “implications of egg shape in an evolutionary and ecological setting.” This egg story is drenched in evolutionary seasoning, to make sure the reader won’t miss the taste.
Can the evolutionary answer stand up to a gentle whiff of questioning? A running theme at CEH is
We should note first that egg shapes are examples of microevolution. Getting a chick to develop in 21 days that can hatch and fly is the big issue for evolution; egg shape and size seem very minor by comparison. We might compare the phenomenon to a magician pulling a rabbit out of a hat. Changing the shape of the hat or the size of the rabbit doesn’t matter as much as being able to do the trick itself. Furthermore, the evolutionary story fails to rule out creation or intelligent design, because advocates of those positions are perfectly happy to see variation in egg shape for different species, and are willing to admit some degree of change over time. So far, then, we don’t see the evolutionary story deserving of privileged status.
The biggest piece of evidence they adduce is the chart showing a correlation between flight behavior and egg shape. It’s an interesting pattern. Correlation, however, does not imply causation. Does the egg shape drive the female bird’s oviduct, or does the oviduct drive the egg shape? If aerodynamic efficiency makes natural selection drive egg shape, one would think it would also drive everything else about the bird, like beak shape and mass. But beaks among strong flyers vary all over the map (consider pelicans, hummingbirds, and Arctic terns). Females only lay eggs when they are not flying, furthermore (for good reason), and what about the males, who don’t have an oviduct? It’s not exactly clear why natural selection would have any influence on egg shape." CEH
