Feathers only rarely fossilize, so the distribution of feathers in dinosaurs is difficult to determine. Sometimes feathers mark the bones, though, and bones do preserve well. Here’s an example: the forearm of a Velociraptor retains an array of small bony bumps evenly spaced along its length. What could they be?
I got some email today with lots of constructive suggestions (See? Not all my email is evil!) for how we ought to change the education of biology students — such as by giving them a foundation in the history and philosophy of our science, using creationist arguments as bad examples so the students can see the errors for themselves, etc. — and it was absolutely brilliant, even the parts where he disagreed with some things I’d written before. Best email ever!
Of course, what helped is that I spent my summer “vacation” putting together a new freshman first semester course for biology majors that I’m teaching for the first time right now, and it’s exactly the course he described. It was eerie, like one of my future students had invented a time machine and come back into the past to tell me what to do. A lot of the course content is locked up behind a password-protected firewall, I’m afraid, but just to show you what I’m talking about, I’ll put the course schedule below the fold.
The vertebrate jaw is a product of evolution — we have a serially repeated array of pharyngeal structures as embryos (and fish retain them in all their bony glory as gill arches), and the anterior most arch is modified during our development to form the jaws. The fact that they’re serially repeated raises an interesting possibility: what if, instead of just the one developing into a jaw, others were transformed as well? You could have a whole series of jaws!
One animal has done exactly that. The moray eel has modified one of the more posterior pharyngeal arches into a second pair of jaws, with a set of muscles that can slide it forward to bite prey already held in the mouth.
When we look at the face of another person, we can recognize specific features that have familial resemblances. In my family, for instance, I can recognize a “Myers nose” that my grandmother and my father and some of my siblings and kids have, and it’s different than my wife’s or my mother’s nose. These are subtle differences in shape—a bit of a curve, a knob, a seam—and their inheritance suggests that these differences are specified somehow in the DNA. If you think about it, though…how can whether the profile of a nose is straight or curved be encoded in a linear stretch of nucleotides? The complicated answer is that it isn’t—morphology is a consequence of epigenetic interactions during development—but we know that the alleles present in the genome do contribute in some significant way to three-dimensional form. How?
We don’t know all the details. This is one of those huge research problems that has gaping holes, full of promise and interest, where we don’t understand exactly how all the pieces fit together. However, here’s an important point that is relevant to other, larger issues in evolution: even where we lack full information about mechanisms, we can roughly perceive the shape of the answer, and that helps us rule out many alternative explanations and guides us in the general direction of a more complete understanding.
People’s noses are a difficult subject for research; we don’t get to define human crosses, people tend to be a little snippy about telling them who to breed with and taking their genes apart, and humans are awfully slow to breed. Fish are better experimental animals, much more pliable and faster and more prolific in their breeding. Some fish, such as the African cichlids, also have highly diverse populations and species with easily recognized and often quite dramatic morphological differences—and we can explore how those differences are generated by genetic and molecular differences in development. In particular, we can start to figure out how fish jaws are shaped by developmental processes.
Once we’ve defeated the creationists (hah!), we’re going to have to manage the next problem: well-meaning but ill-informed animal rights activists. Nick describes a recent article that tries to claim we can reduce animal use in labs — and it even has a couple of respectable scientists signing on to that nonsense.
And it really is nonsense. We don’t understand everything that is going on inside animals, and to figure it out, we actually need to look inside them. There’s no other way. If you want to examine patterns of gene expression inside the developing mouse brain, you have to extract their brains (needless to say, a lethal process) and examine them with a host of tools. Isolated cells in a petri dish aren’t the same thing. To simulate something with a computer, you need to know the parameters of what you’re simulating.
Using our imaginations and inventing what we think might be going on rather easily leads to absurd results … and the way I recognized that they were absurd is that I’ve actually looked at the processes involved.
Look into this one, everyone: the Coalition on the Public Understanding of Science (COPUS), another attempt to coordinate efforts to improve public outreach and science education. They have some worthy goals:
- Building the COPUS network – Underpinning the COPUS effort is a growing network of organizations and individuals who share a common goal: engaging sectors of the public in science and increasing their appreciation and understanding of the scientific enterprise. Find out more about participating in the COPUS Network.
- Developing state-level benchmark science-indicator reports on the importance of science to the U.S. economy and standard-of-living
- Supporting a national effort to promote the public understanding of science in a year-long celebration: Year of Science 2009 (also available: Year of Science 2009 fact sheet [PDF])
- Integrating efforts with the Understanding Science website project currently under development at the University of California, Berkeley
If you’re involved with any kind of scientific outreach organization, register with them — they’ve got a long list of science groups. I particularly like the fact that they’re herding together a grassroots effort to celebrate a Year of Science in 2009, the Darwin bicentennial year, since there doesn’t seem to be any national leadership on the issue otherwise.
Some of you may have never seen an arthropod embryo (or any embryo, for that matter). You’re missing something: embryos are gorgeous and dynamic and just all around wonderful, so let’s correct that lack. Here are two photographs of an insect and a spider embryo. The one on the left is a grasshopper, Schistocerca nitens at about a third of the way through development; the one on the right is Achaearanea tepidariorum. Both are lying on their backs, or dorsal side, with their legs wiggling up towards you.
There are differences in the photographic technique — one is an SEM, the other is a DAPI-stained fluorescence photograph — and the spider embryo has had yolk removed and been flattened (it’s usually curled backward to wrap around a ball of yolk), and you can probably see the expected difference in limb number, but the cool thing is that they look so much alike. The affinities in the body plans just leap out at you. (You may also notice that it doesn’t seem to resemble a certain other rendition of spider development).
Aaargh. When will the media learn? National Geographic is running this ridiculous headline right now: New Fossil Ape May Shatter Human Evolution Theory, in which the reporter claims a discovery of some teeth could “demolish a working theory of human evolution.” It’s not true. Where is this nonsense coming from?
I read the article. It’s titled “A new species of great ape from the late Miocene epoch in Ethiopia.” The exciting news is that the “combined evidence suggests that Chororapithecus may be a basal member of the gorilla clade, and that the latter exhibited some amount of adaptive and phyletic diversity at around 10-11 Myr ago.” It concludes with a suggestion that we need to do more research in sediments appropriate to Miocene apes. There aren’t an exploding paradigms or revolutions suggested.
I read the associated news article in Nature. It’s titled “Oldest gorilla ages our joint ancestor.” It says that this discovery pushes back the time of divergence of the gorilla lineage from our own. This is just ordinary science.
Now read the blogs — they’re doing a much better job of evaluating this work than the traditional media. For one thing, they’re actually looking at it critically. Afarensis points out that these are only a few teeth, and it’s awfully thin grounds for a substantial revision of the timeline. John Hawks makes a similar point, but also highlights the fact that there is an unresolved problem — we need to reconcile paleontological and molecular dates. Even John Wilkins, a “mere” philosopher, weighs in sensibly that teeth are plastic characters in phylogeny, and deplores this peculiar media habit of taking a recalibration of a historical detail as a major reformulation of theory. All these discussions are sober and interested and most important of all, accurate.
The lesson is clear: when you see some wild and crazy claim of scientific revolutions and the demolition of long-held theories, go immediately to the science blogs for some clear-eyed sanity and informed evaluation from experts.
Yesterday’s discussion of future biological advances that will piss off the religious right had me thinking about other innovations that I expect will happen within a few decades that might just cause wingnuts to freak out. First thing to come to mind is that it will be something to do with reproduction, of course, and it will scramble gender roles and expectations…so, how about modifying men to bear children? It sounds feasible to me. Zygotes are aggressive little parasites that will implant just about anywhere in the coelom — it’s why ectopic pregnancies are a serious problem — so all we need to do there is culture a bit of highly vascularized tissue in the male abdomen that will serve as a secure home for a few months. We’ll have to play some endocrine games, too, which may effect his love life but will also prepare him to lactate post-partum. There’s the minor anatomical problem that the vagina is a unique tissue, and no, the urethra is not homologous or analogous (fortunately; we wouldn’t want to have to push an 8 pound baby through the penis, even if female hyenas can manage it) — but that’s what c-sections are for. Given money, time, and a few weird volunteers, it could be done.
The next question is, has it been done? Are there any other vertebrates that have males doing the hard work of pregnancy? There were the gastric brooding frogs, which one would think could have made the leap easily — the eggs were just swallowed and developed in the stomach — but only the mothers seemed to have done the job. They’re all extinct, anyway. Male frogs of the genus Rhinoderma brood their young in their mouths, but this is after external fertilization and development, so they’re actually simply holding larvae in a safe place — and they’re also endangered. The precedents aren’t promising.
There is an extremely interesting and successful example, though: the syngnathid fishes, sea horses and pipefish. In all 232 species, the female lays her eggs in a specialized male structure called the brood pouch, where they are fertilized and develop. It’s a true male pregnancy!
It’s nice to see these casual references to PZ Myers, as if anyone would have heard of me:
The lab is at 101 Theory Drive, a developer’s idea of a scientific street name that Lynch found presumptuous.
It is a mark of the difficulty of life sciences — biology and its many descendants — that to call something a theory is to honor, not slight it. Theory, evolutionary biologist P.Z. Myers has written, is what scientists aspire to. Lynch, for all of his bombast, was respectful of the intellectual protocols of his science.
“I would have called it Hypothesis Drive,” he said.
The article is part of an interesting series on research into learning and memory, that is also unfortunately marred by some casual sexism on the part of its subject. See, Zuska, you just had to ruin it for me!
P.S. I think of myself as more of a developmental biologist than evolutionary biologist, but OK, I am very interested in evolutionary issues.
