Drifted Apart, Crammed Together

As organisms spread into new habitats, they diverge and differentiate to best adapt to their surroundings. But when separated species exploit similar niches, their body plans begin to converge, and they end up looking a lot like each other. Such is the case with Beaked Sea Snakes, uber-venomous consumers of spiny catfish and blowfish, long thought to be a single species but now shown by genetic analysis to be two. Meanwhile, PZ Myers considers the Creationist discipline of baraminology, which self-consciously strives to minimize the number of animals Noah needed to fit on his ark. Dr. Jean K. Lightner counts only 137 progenitors of modern mammals, meaning there has been an awful lot of evolution since the flood. Still, it’s hard to explain a Beanie Baby in the wild without invoking Intelligent Design.


Animal Bodies Rearranged

On Pharyngula, PZ Myers considers a computer model which posits that bones are simply exoskeletons turned inside-out. Myers writes “We know from the homology of the patterning molecules involved that vertebrates and invertebrates are upside-down relative to each other, so at some point an ancestor flipped.” Such major differences in body plan arise during embryonic development, driven by highly evolved genetic instruction. But the growth of internal and external skeletons depends on distinct biological mechanisms, leading PZ to call the dataless computer model “abiological and ahistorical bollocks.” PZ proves his point with the turtle, a vertebrate that also has an insect-like shell. He explains, “The ribs and vertebrae are ‘endoskeletal’, formed by chondrogenesis and ossification, while the scutes or plates of the shell are dermal bone,” and where they meet “represents the fusion of two kinds of bone.” But how did the turtle’s shoulder blades get inside its rib cage? Allow PZ to explain…

Divergent & Convergent Evolution

On ERV, Abbie Smith reports that scientists have discovered an entirely new branch of viruses in the boiling acid pools of Yellowstone National Park. By analyzing RNA segments from the pools, researchers inferred the existence of positive-strand RNA viruses with unknown genetic configurations. Smith writes, “These viruses are not just kinda new. They are really really different from the RNA viruses we already know about!” They infect primordial single-celled organisms called Archaea which thrive in the extreme heat of the pools. On the multicellular side of life, Dr. Dolittle shares the first pictures of “a new family of limbless caecilian amphibians” from India. Although they look like worms, “genetic testing and comparative analyses of their cranial anatomy show that they are in fact an ancient lineage of amphibians that first appeared ~140 million years ago.”  This seems like a clear example of convergent evolution–does living in the dirt lead one to look like an earthworm?  Or do these caecilians gain some advantage through resemblance?

Anticlimactic Research

A new paper published in the journal Animal Behavior tackles the origin of the female orgasm—does it have gender-specific advantages, or is it merely a byproduct of male adaptations? Having polled 10,000 twins about their orgasmic tendencies, researchers found “no significant correlation between opposite-sex twins and siblings” and therefore concluded that “selection pressures on male orgasmic function do not act substantively on female orgasmic function.” PZ Myers writes “the logic of this experiment falls apart at every level.” He points to the inevitable biases that affect self-reporting, and the fact that researchers asked male and female twins qualitatively different questions. PZ concludes, “I’d consider it extremely unlikely that female orgasm doesn’t use exactly the same genetic apparatus as male orgasm.” Greg Laden criticizes the research as well, writing “the reason that the Zietsch and Stanttila paper is wrong, in my view, is because it asks the wrong question in the wrong way with an incorrect understanding of what they are studying and why.” Greg says most researchers are (figuratively) blinded by the ejaculation of seminal fluid by males. And he offers some very interesting insights into the development of erogeneity in primates, and its refinement in the human species.

Evidence, Layer by Layer

Evidence that life on Earth is very old (and of humble origin) continues to accrue, but some beliefs are insurmountable. On EvolutionBlog, Jason Rosenhouse refutes the argument that the evolution of complex molecules and organisms is highly improbable. He notes that if we “imagine evolution proceeding by selecting genotypes entirely at random, then the probability is vanishingly small that we shall ever find one that produces a functional, complex organism.” But since natural selection only builds upon what works, it’s a smaller wonder that we’re here to argue about it. On Dispatches from the Creation Wars, Ed Brayton exposes “the problems that flood geology has trying to jam every single event recorded in nearly 700 million years of deposition into a single year.” Ed writes, “one has a hard time imagining how a group of dinosaurs were alive and going about their day, peacefully building nests to hatch their young on solid ground, in the midst of a global flood that had already deposited thousands of feet of sediment below them.” Who says the Word of God can’t be poetic?


On Dean’s Corner, Jeffrey Toney reports the winners of Google’s first Science Fair, and in all age groups the winner was a girl. They researched some very challenging and relevant topics: Lauren “studied the effect of different marinades on the level of potentially harmful carcinogens in grilled chicken,” Naomi “endeavored to prove that making changes to indoor environments that improve indoor air quality can reduce people’s reliance on asthma medications,” and Shree “discovered a way to improve ovarian cancer treatment for patients when they have built up a resistance to certain chemotherapy drugs.” On a mostly unrelated note, Josh Rosenau transcribed the responses of all 50 Miss USA contestants to the question, “Should evolution be taught in schools?” While most said we should teach “both sides,” winner Miss California said “I was taught evolution in my high school growing up, and I do believe in it, I mean I’m a huge science geek, so I like to believe in like the big bang theory, and you know, the evolution of humans you know, throughout, you know, time.” Amen to that, sister.

Chromosomes, X and Y

i-c391e5995011d135267ae80c0253f87d-somebuzz.jpgOn Neurotopia, Scicurious offers a refresher course on mitosis. This vital process occurs every time a cell divides, as centrosomes pull apart replicated chromosomes with microtubules. Normal cell mechanics limit this “molecular tug of war” to about 50 iterations, meaning we can’t keep splitting chromosomes forever. But we can use meiosis make some babies. On Gene Expression, Razib Khan explains that the X chromosome is relatively scarce since males only carry one copy of it, while all other chromosomes travel in pairs. This makes the X chromosome “more susceptible to stochastic fluctuations in frequency such as random genetic drift,” causing it to exhibit “greater between population variance” than the genome as whole. And on Not Exactly Rocket Science, Ed Yong stands up for X’s puny boyfriend the Y, a chromosome that once jettisoned “around 97% of its original genes.” These days, the human Y chromosome is definitely up to something, having racked up 310 million years worth of evolutionary change in the 6 million years since chimps and humans shared a common ancestor.

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