This is just to let you know that I'll be going on a wee hiatus to attend the annual Writers' Retreat held by my publisher, Oghma Creative Media, in the lovely Ozark Mountains. So I'll be away for two weeks, and will be back in the saddle on Monday, August 12. Please keep sending me ideas and links, making comments on posts, and so on -- I always love hearing from my readers.
Until then, hoist high the banner of skepticism!
The lovely thing about science is that you never have a reason to stop learning.
I just retired after teaching biology for 32 years, and the area of biology I studied the most (and enjoyed teaching the most) was evolution and phylogeny. I'm not a researcher, and nowhere near a specialist (I've been called a "dabbler" and a "dilettante," and I don't think they were meant as compliments), but I think that about those topics I'm at least Better Than the Average Bear.
So I was a little surprised yesterday to run into a group of ancient mammals I had honestly never heard of. They're called docodonts, and technically I misspeak by calling them "mammals;" they're mammaliforms, which sounds like a species of alien on Doctor Who but isn't. The docodonts and other mammaliforms are cousins of modern mammals, seem to have left no living descendants, and are more like mammals than they are like any other extant group. Take, for example, this docodont, Castorocauda (the name means "beaver-tail"):
[Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Castorocauda BW, CC BY 3.0]
The reason this comes up is the discovery of a mid-Jurassic docodont whose skeleton shows some remarkably mammal-like features. This little guy, called Microdocodon (evidently named by someone who believes in keeping things simple and obvious) was around 165 million years ago, which (for reference) is a good hundred million years before the non-avian dinosaurs became history.
What's interesting about Microdocodon is that it had a mammalian hyoid bone -- unique in our skeleton as the only bone that does not articulate with another bone. It's a horseshoe-shaped bone that connects to the tongue, epiglottis, larynx, and muscles that support the neck, and gives us our ability to chew, swallow, keep an open airway while we're asleep -- and talk.
In non-human mammals, it's all about the first three, and it's thought that the evolution of the hyoid bone was instrumental in improving the range of food mammals could eat, since the ability to chew meant they weren't confined to swallowing big chunks of food at once.
"It is a pristine, beautiful fossil. I was amazed by the exquisite preservation of this tiny fossil at the first sight," said Zhe-Xi Luo, a professor of biology at the University of Chicago and lead author of the study, which appeared in Science last week. "We got a sense that it was unusual, but we were puzzled about what was unusual about it After taking detailed photographs and examining the fossil under a microscope, it dawned on us that this Jurassic animal has tiny hyoid bones much like those of modern mammals... Now we are able for the first time to address how the crucial function for swallowing evolved among early mammals from the fossil record. The tiny hyoids of Microdocodon are a big milestone for interpreting the evolution of mammalian feeding function."
The most amazing thing about all this is that Microdocodon catches evolutionary remodeling of a pre-existing skeleton right in midstream. "Hyoids and ear bones are all derivatives of the primordial vertebrate mouth and gill skeleton, with which our earliest fishlike ancestors fed and respired," said Bhart-Anjan Bhullar, postdoctoral scholar at Yale University and co-author of the paper. "The jointed, mobile hyoid of Microdocodon coexists with an archaic middle ear -- still attached to the lower jaw. Therefore, the building of the modern mammal entailed serial repurposing of a truly ancient system."
So that's our lens into the past for today, and a look at a group of mammal relatives that until I read this paper, I didn't even know existed. All of this making me question how anyone can think science is boring. If after studying and/or teaching science over the past forty years I can still find something new and astonishing, you have to appreciate science's capacity for inducing awe -- and wonder what new discoveries lie ahead.
The subject of Monday's blog post gave me the idea that this week's Skeptophilia book recommendation should be a classic -- Konrad Lorenz's Man Meets Dog. This book, written back in 1949, is an analysis of the history and biology of the human/canine relationship, and is a must-read for anyone who owns, or has ever owned, a doggy companion.
Given that it's seventy years old, some of the factual information in Man Meets Dog has been superseded by new research -- especially about the genetic relationships between various dog breeds, and between domestic dogs and other canid species in the wild. But his behavioral analysis is impeccable, and is written in his typical lucid, humorous style, with plenty of anecdotes that other dog lovers will no doubt relate to. It's a delightful read!
[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]
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