The cover story of New Scientist asks, “Was Darwin wrong?”, as if this were surprising news (he was wrong about many things) or as if the discovery of new details would somehow demolish the whole structure of evolutionary theory. I’ll let Larry Moran take care of this one.
It’s a symptom of creationist influence that journals would think that hyping a story that “150 year old theory gets revised!” is newsworthy. And, of course, the creationists are eating it all up.
Usually, Begley is reasonably good on science, but her latest piece is one big collection of misconceptions. It reflects a poor understanding of the science and of history, in that it confuses long-standing recognition of the importance of environmental factors in gene expression with a sudden reinstatement of Lamarckian inheritance, and it simply isn’t — she’s missed the point of the science and she has caricatured Lamarck.
Some water fleas sport a spiny helmet that deters predators; others, with identical DNA sequences, have bare heads. What differs between the two is not their genes but their mothers’ experiences. If mom had a run-in with predators, her offspring have helmets, an effect one wag called “bite the mother, fight the daughter.” If mom lived her life unthreatened, her offspring have no helmets. Same DNA, different traits. Somehow, the experience of the mother, not only her DNA sequences, has been transmitted to her offspring.
That gives strict Darwinians heart palpitations, for it reeks of the discredited theory of Jean-Baptiste Lamarck (1744-1829). The French naturalist argued that the reason giraffes have long necks, for instance, is that their parents stretched their (shorter) necks to reach the treetops. Offspring, Lamarck said, inherit traits their parents acquired. With the success of Darwin’s theory of random variation and natural selection, Lamarck was left on the ash heap of history. But new discoveries of what looks like the inheritance of traits acquired by parents–lab animals as well as people–are forcing biologists to reconsider Lamarckism.
She’s describing real and interesting phenomena, but it isn’t new and it isn’t revolutionary. These are results of plasticity and epigenetics, and we aren’t having heart palpitations over them (you’re also going to have a difficult time finding any “strict Darwinians” in the science community who are even surprised by this stuff). We load up pregnant women with folate and maternal vitamins and recommendations to eat well, and we tell them not to get drunk or smoke crack for a few months, because it is common sense and common knowledge that extra-genetic factors influence the health and development of the next generation. Genes don’t execute rigid, predetermined programs of development — they are responsive to the environment and can express radically different patterns in different contexts. The same genes build a caterpillar and a butterfly, the difference is in the hormonal environment that selects which genes will be active.
It’s the same story with the water fleas. Stressed and unstressed mothers switch on different genes in their offspring epigenetically, which lead to the expression of different morphology. It’s very cool stuff, but evolutionary biologists are about as shocked by this as they are by the idea that malnourished mothers have underweight babies. That environmental influences can have multi-generational effects, and that developmental programs can cue off of the history of the germ line, is not a new idea, especially among developmental biologists.
This is just wrong on evolution:
Water fleas pop out helmets immediately if mom lived in a world of predators; by Darwin’s lights, a population of helmeted fleas would take many generations to emerge through random variation and natural selection.
It misses the whole point. The population of water fleas have a genetic attribute that allows the formation of spines under one set of conditions, and suppresses them under others. This gene regulatory network did not pop into existence in a single generation! If it did, then Begley would have a big story, evolution would have experienced a serious blow, and we’d all be looking a little more carefully into this ‘intelligent design’ stuff. The pattern of gene regulation was the product of many generations of variation and selection; only the way it was expressed in a phenotype experienced a shift within a single generation.
It’s also not Lamarckism. It’s another of those short and simple-minded myths perpetuated by high-school textbooks that Lamarck and Darwin had competing explanations for the same phenomena. They did not. This story of giraffes stretching their necks is an example of the purported inheritance of acquired characteristics … and here’s some headline news, Darwin proposed exactly the same thing! Darwin did not have a solid theory of heredity, and he himself proposed a mechanism of pangenesis which permitted the inheritance of characters by use and disuse and by injury or malformation. The key difference is that Darwin proposed that these variations could lead to the formation of new species; Lamarck believed in the fixity of species, and thought that a species would merely express a constrained range of forms in differing environments.
Both were wrong. A concept called the Weismann barrier emerged in the late 19th century, which suggested that the only influences that can be transmitted across generations are those that affect the germ line, the cells that give rise to sperm and egg, and that modification of the somatic tissues alone would not propagate. This is correct, and it’s still true: nothing in these reports suggest anything but that when perturbed by environmental stressors, gametes can switch on different genetic programs.
I think epigenetics and plasticity are important and play a role in evolution, certainly, but these kinds of elaborations on how cells interact do not imply in any way that there is a revolution in evolution, or that evolutionary biology has had it all wrong, or that this is heresy in progress. It’s also annoying to see all the vague handwaving about discrediting a “Darwinian model” — what Darwinian model? These discoveries are about mechanisms of genetic inheritance, and Darwin didn’t have a valid mechanism in the first place. In that sense, the only real heresy that counted was Mendel’s.
First, a warning: this is a link to a good science article, but it’s hosted on the Suicide Girls site, which contains many pictures of young ladies with attitude and tattoos in a state of deshabille. You may discover you are blocked at work. But do persevere! It will be worth it even if you have no interest in naked women!
Anyway, one of the broad points of dissension in the discussion of the evolution of religion can be split along one general question: was religion directly adaptive in the evolution of humans, or was it more of a side-effect of other useful cognitive and social properties? I’m on the side of the side-effect gang, and so this article on the evolution of religion jibes nicely with my position. And I really like this simple analogy:
The reason religion is so successful is that it taps into our primal-brains in much the same way that a Big Mac does — only more so. Religion gained its foothold by hijacking the need to give purpose at a time when humans had only their imagination — as opposed to the evidence and reason that we have today — to fathom their world. Spirits and demons were the explanation for illnesses that we now know are caused by bacterial diseases and genetic disorders. The whims of the gods were why earthquakes, volcanos, floods and droughts occurred. Our ancestors were driven to sacrifice everything from goats to one another to satisfy those gods.
Greasy, fatty, substanceless, and not at all good for you…but it tastes so good, and it’s cheap and readily available everywhere. That’s religion and fast food.
So read the whole thing, even if you do have to wait until you get home tonight.
You should mark your calendars now…oh, wait, you’re all godless neodarwinist stooges, so you’ve already got Darwin Day colored in with circles and arrows and hearts. OK, so you should add an annotation if you live somewhere near Minneapolis, because the Bell Museum is sponsoring a special Darwin Day Cafe Scientifique, which will combine art and science to tell the story of evolution.
LIFE: A Journey Through Time
North American Premiere /Darwin Day Opening Event
Thursday, February 12, 2009, 7 to 9 p.m.
Bell Museum Auditorium
$10/ free to museum members and University studentsCelebrate the 200th anniversary of Charles Darwin’s birthday with a special preview of LIFE: A Journey Through Time. The event will feature top University biologists using Lanting’s photographs as a springboard to deliver a rapid-fire presentations relating their research on evolution to the images. From the big bang to the human genome, hear the newest theories on how life evolved and enjoy the North American premiere of one the world’s most celebrated photography exhibits. Think speed-dating – Darwin-style!
This event is also the premier of an exhibit of a stunning collection of nature photography. You should go to that, too.
LIFE: A Journey Through Time
February 14 – April 12, 2009The University of Minnesota Bell Museum of Natural History is proud to host the North American premier of this internationally acclaimed exhibit. LIFE: A Journey Through Time, interprets the evolution of life on Earth through photographer Frans Lanting. Lanting’s lyrical photos trace Earth’s history from the beginnings of primordial life to the ascent of mammals through otherworldly landscapes and breathtakingly intimate portraits of animals and plants engaged in million-year-old rituals. Many of the exhibit’s 62 photographs are matched with real animal, fossil, and plant specimens from the Bell Museum’s collection. Born in the Netherlands, Lanting serves on the National Council of the World Wildlife Fund and is a columnist for Outdoor Photographer and has received the BBC Wildlife Magazine’s Wildlife Photographer of the Year Award and the Sierra Club’s Ansel Adams Award for Conservation Photography.
One other special feature is that the speakers (I’m one of them) are going to present in Pecha Kucha style. This could be interesting, too.
Pecha Kucha (usually pronounced in three syllables like “peh-chach-ka”) was started in Tokyo, Japan in February 2003 by Astrid Klein and Mark Dytham as a designers’ show and tell event to attract more people to SuperDeluxe, their multi-media experimental event space they had set up in Roppongi.
The idea behind Pecha Kucha is to keep presentations concise, the interest level up and to have many presenters sharing their ideas within the course of one night. Therefore the 20×20 Pecha Kucha format was created: each presenter is allowed a slideshow of 20 images, each shown for 20 seconds. This results in a total presentation time of 6 minutes 40 seconds on a stage before the next presenter is up.
I’m planning to talk about the evolution of multicellularity…with 20 slides in 6 minutes and 40 seconds. We’ll see how that goes.
We’re one step closer to self-sustaining chemical replicators, similar to what would have existed a few billion years ago, before true cells evolved. Lincoln and Joyce have created a couple of relatively simple molecules that assemble themselves from even simpler precursors in a test tube.
It’s not as straightforward as the simplest scheme one might imagine. The simplest model would be for a single enzyme, E, to catalyze its own assembly from two smaller precursors, A and B. This formula would lead to a test tube full of A and B to be quickly converted to a test tube full of nearly nothing but E with the introduction of a single copy of E. The actual solution is a little more difficult to explain.
Those Brits keep showing us up by unashamedly trumpeting good science on television and radio. The BBC has a whole collection of media on Darwin right now, most of it good.
Most. One thing I simply do not get is the infatuation with the idea that evolution has stopped for humans. I am baffled at how anyone can take such an idea seriously, yet there’s Steven Jones again making this peculiar claim.
Spiders are amazingly sophisticated animals, and probably the premiere complex adaptation of modern spiders is the ability to spin silk. They have multiple internal glands that can produce multiple kinds of silk — webs contain different kinds, from structural strands to adhesive strands, and other kinds are used for spinning egg cases and for wrapping prey — and they are sprayed out through small spigots mounted on swiveling spinnerets, which are modified opisthosomal (abdominal) limbs. Obviously, these detailed features did not spontaneously appear all at once, but had to have evolved progressively. A couple of fossils have recently been described that reveal a) silk spinning is ancient, from at least the Permian, but that b) these early spiders did not have the full array of modern adaptations.
Here is a pair of fossils: Permarachne novokshonovi, from the Permian in Russia, and a more recent specimen, and Palaeothele montceauensis, from the Carboniferous in France. Both are eight-legged arthropods, and if you saw one scuttling about now you wouldn’t hesitate to call them spiders. There are some differences, though: Permarachne in particular shows a little less tagmosis, or fusion and specialization of segments, than we usually see in spiders, and it also has that prominent flagellum (which is completely different from a bacterial flagellum!), a long segmented ‘tail’ covered with sensory hairs that was probably a sense organ; it has no sign of a web-spinning function.
What about the production of silk and webs in these old spiders? Here’s another specimen, Attercopus fimbriunguis, a 376 million year old fossil. It’s a little less dramatic because these are fragments of cuticle that have been carefully extracted by dissolving the rocky matrix with acid; it means, unfortunately, that it is more fragmented, but the advantage is that now we can zoom in microscopically and see far more detail in the structure. What we can now see in pieces of the ventral plates of the opisthosoma are small spigots, and in a few cases, there are even strands of spider silk still extended from these pores. In F, there’s also a nice shot of a chelicera (fang) from the spider — it’s wicked sharp, but the small holes seem to be preservation artifacts, and there’s no sign that venom secretion, another important spider adaptation, has evolved yet.
One of the critical observations here is very simple: no spinnerets. These spiders did not have the modified limbs with sets of spigots that we see nowadays, but instead, had a series of spigots arrayed across the bottom of the abdomen. They almost certainly were not able to make webs: what they could have done was produce sheets of silk, of the kind that could be used to make egg cases or wrap around prey. These are another example of a transitional fossil, forms that have only some of the capabilities of a later organism.
(via Cheshire, who promises to have his own post on this paper soon.)
Selden PA, Shear WA, Sutton MD (2008) Fossil evidence for the origin of spider spinnerets, and a proposed arachnid order. Proc Nat Acad Sci USA 105(52):20781-20785.
This week, Nature magazine published a short list of recent important developments in evolutionary biology that support the theory of evolution, as a tool to help explain that evolution is definitely a dynamic and useful theory in our field and to demonstrate that the evidence is still growing. Here’s a short summary of the 15 stories the editors picked out, but you should also read the freely available article, 15 Evolutionary Gems. Teachers, put this in your classroom!
The discovery of Indohyus, an ancestor to whales.
The discovery of Tiktaalik, an ancestor to tetrapods.
The origin of feathers revealed in creatures like Epidexipteryx.
The evolution of patterning mechanisms in teeth.
The developmental and evolutionary origin of the vertebrate skeleton.
Speciation driven indirectly by selection in sticklebacks.
Selection for longer-legged lizards in Caribbean island populations.
A co-evolutionary arms race between Daphnia and its parasites.
Non-random dispersal and gene flow in populations of great tits.
Maintenance of polymorphisms in populations of guppies.
Contingency in the evolution of pharyngeal jaws in the moray.
Developmental genes that regulate the shape of beaks in Darwin’s finches.
Evolution of regulatory genes that specify wing spots in Drosophila.
Evolution of toxin resistance.
The concept of evolutionary capacitance: the idea that environmental stress can expose hidden variations that are then subject to selection.
Here’s an interesting new blog, Moneduloides, that seems to have an emphasis on human evolution, if you’re into that sort of thing, and it currently has a short list of good texts for Christmas presents. <moan> I’ve done absolutely no Christmas shopping at all this year, so if the economy tanks and my family hates me, it is all my fault. I just have to get out from under this stack of grading first.
