Tag Archives: Evolution

How do snails coil?

Typically, snails coil as they grow. The exact shape and characteristics of the coil are known to be a combination of genetic and environmental factors, depending on the snail. There is an interesting story involving snails and the young Jean Piaget. Piaget is famous for his work in psychology, but before that, when he was quite young, he worked with birds and mollusks. His work was published and otherwise disseminated and experts in these areas, unaware that he was a teenager, assumed he was an adult expert on natural history. Anyway, Piaget studied, among other things, a group of snail species in the Alps that had a diverse range of shapes from roundish to more elongated. It appeared that these snails were well adapted to their environment. Elongated snails, which are more delicate than round ones, lived in low energy environments such as lakes, while the round ones were found in quickly running water, where being round gave more mechanical protection from getting bashed about.

As part of his research he collected specimens of these snails from lakes and various streams, and raised them in aquariums. When the snails of the various species grew up in the aquariums, they all looked like each other (they looked like the still water lake snails); the morphology that separated these different species in the wild vanished in the lab. It turned out that the snails differentiated via some sort of reaction to their environment. What seems to have been an excellent example of Darwinian adaptation was actually an excellent example of norm of reaction (the range of variation a given genotype produces in various environments).

Piaget also studied a group of plants in the same region that exhibited the same phenomenon; viny, bushy, tree-ish, etc. forms were the same species growing in different habitats. Between the snails and the plants, Piaget is said to have more or less given up on “Darwinism.” He was wrong, of course. Rejecting Darwinian concepts of evolution gave Piaget the chance to become a very famous psychologist but he lost the opportunity to explore and publish on a key feature in evolutionary biology, reaction norms.

ResearchBlogging.orgBut enough of reaction norms. Most of the morphological differences between snail species is probably more genetic than it is environmental, despite Piaget’s bad luck in choice of model species. Some years ago I had the pleasure of working with fresh water snail expert Pete Williamson, and from him I learned that one way to differentiate among species of snails was to develop a polynomial formula that described the shape of the coiled shell. One could then measure a number of individuals and assign variance terms to each element of the polynomial, and in this way test hypotheses about differences between species or subspecies, or evolutionary change over time. Pete’s work on African fresh water snails was one of the first examples of punctuated equilibrium to be worked out in a major taxon following Gould and Eldridge’s definition of that concept. He also was able to pin down various “turnover” events when a number of species went extinct and new ones arose that associated in time with key events in human evolution in East Africa. (I talk about Pete in some of my Congo Memoirs, starting with this one. He’s piloting the boat we were in that sank in Lake Edward.)

And all this leads us to a new paper, published in BioMed Central’s open access journal EvoDevo. The press release I received this morning seems quite good so I’ll just reproduce it below. The paper, being Open Access, is available here. (Let me know if that link does not work for you!)

Snail shell coiling programmed by protein patterning

Snail shells coil in response to an lopsided protein gradient across their shell mantles, finds research in BioMed Central’s open access journal EvoDevo. In contrast the shell mantle of limpets, whose shells do not coil, have a symmetrical pattern of the protein Decapentaplegic (Dpp).

There are many hundreds of different kinds of gastropods (slugs snail and limpets) – second only in number of species to insects. They have adapted to live on land as well as in fresh water and marine environments, and have altered their physiology to survive in different habitats and to exploit different niches. The ancestral snail is thought to have had a coiled shell but during evolution some snails have lost their shells to become slugs, and some, limpets and false limpets, have independently lost the ability to coil their shells.

In order to find out why some gastropods have straight and some have coiled shells researchers from the University of Tokyo looked at the pattern of Dpp during shell growth. Dpp was first identified in fruit flies where it is necessary for the correct development of limbs, wings and other organs – decapentaplegic describes the 15 things missing in the absence of the gene dpp. Dpp is also found in the shell gland of gastropods, an early structure which begins to form a developing shell. However its presence in the mantle, which takes over shell production as the animal develops, was unknown.

In all four animals tested, limpets Patella vulgata and Nipponacmea fuscoviridis, and the right-hand coiled pond snail Lymnaea stagnalis along with a sinistral coiled lab-developed snail, dpp expression matched shell shape. There was also a Dpp protein gradient spreading away from this which was also symmetrical in limpets but had left/right asymmetry for the pond snails, matching the handedness of shell coiling.

Keisuke Shimizu, who led this study, commented, “This molecular mechanism driving for shell coiling persists from early developmental stages though adult life as the shell is replaced. It also provides an explanation for how shell coiling has been lost several times during the evolution of gastropods by the relatively easy loss of asymmetric Dpp.”

Here’s a picture:

Snail Evolution
Snail Evolution

Shimizu, K., Iijima, M., Setiamarga, D., Sarashina, I., Kudoh, T., Asami, T., Gittenberger, E., & Endo, K. (2013). Left-right asymmetric expression of dpp in the mantle of gastropods correlates with asymmetric shell coiling EvoDevo, 4 (1) DOI: 10.1186/2041-9139-4-15

If a spider is in an Oreo Cookie, then evolution is true!

You know about the Atheists Nightmare, right? Also known as the Evolutionists Nightmare. No? It goes like this:

That’s pretty darn convincing. Until someone opens up some closed thing and there is some new species in there, then EVOLUTION IS MADE UP!!!1!!!

Well, it turns out, Evolution is True. Some guy on the internet opened up an Oreo Cookie and inside was a new organism that could only be there IF IT EVOVED IN SIDE THE COOKIE!!1!! Look here’s a picture:

spider evolved inside oreo cookie
PROOF THAT EVOLUTION IS TRUE: This spider evolved inside this Oreo Cookie!

A fake you say? A falsehood you say? Sorry, but Snopes was unable to disprove that this spider appeared spontaneously inside this cookie. Indeed, we all know that stuff that can’t happen happens all the time. If anything, Snopes will declare something false even when they can’t, so clearly, this spider did evolve in this Oreo Cookie.

Evolution. It’s real.

BTW, if this happens to you and creates a spider problem in your house, we can fix that.

New Evidence that the Bible is Wrong on Evolution

I find the following bit of video to be very interesting. The letter itself, which they read at the beginning, is instructive of why many people are creationists or otherwise anti-science. They are afraid to go to hell. The idea that a person will go to hell for believing in science is something you have to be taught. The people who teach this should … well, they can go to hell, as far as I’m concerned. Continue reading New Evidence that the Bible is Wrong on Evolution

A Remarkable Convergence of Species: The Deadliest Sea Snake

ResearchBlogging.orgSea snakes are true snakes that look a little like eels because of their horizontally flattened rudder-like tails, and they spend a lot of time…for most species, their entire lives…in the ocean. Only one species seems to be able to move on land at all. They seem to all be venomous, some extremely so. They are all tropical or near-tropical, and there are numerous species distributed among about 15 genera.

One species is Enhyrina schistosa, known as the Beaked Sea Snake, or the Hook-Nosed Sea Snake. It lives in the waters near Indonesia and Australia. This is known to be the most venomous of all of the sea snakes, and a certain number of people are bitten by them. In fact, most people who die of sea snake bites were bitten by Enhyrina schistosa. How many people get bitten by them? Hard to say. In Australia, between 1942 and 1950, 56 people died from sea snake bites. What is the meaning of that number? Hard to say; it is just one of those esoteric bits of information one finds in Wikipedia. These snakes probably don’t bite very many people, but when they do, you have a problem.

The Beaked Sea Snake feeds mainly on spiny catfish and blow fish, and as such benefits from have a large gape. Selection for the large gape has altered the morphology of this snake in a way that probably contributes to it’s beaked nose and a couple of other features that are used to distinguish it from other sea snakes and thus identify it to species. The problem is, this selection pressure seems to have caused two distinctly different groups of snakes (actually, three … see below) to converge on a single morphology. So, what we have been calling Enhyrina schistosa, the beaked sea snake, is clearly two distinct species that look enough alike to have been confused as one. This is destine to be a classic example of evolutionary convergence.

This is all being reported in a paper due out soon in Molecular Phylogenetics & Evolution by Kanishka D.B. Ukuwela, Anslem de Silva, Mumpuni, Bryan G. Fry, Michael S.Y. Lee and Kate L. Sanders. Caroline Bird of the University of Queensland Communications Office provided some background and the great snake picture.

From the abstract of the paper:

We present a striking case of phenotypic convergence within the speciose and taxonomically unstable Hydrophis group of viviparous sea snakes. Enhydrina schistosa, the ‘beaked sea snake’, is abundant in coastal and inshore habitats throughout the Asian and Australian regions … Analyses of five independent mitochondrial and nuclear loci for populations spanning Australia, Indonesia and Sri Lanka indicate that this ‘species’ actually consists of two distinct lineages in Asia and Australia that are not closest relatives. As a result, Australian ‘‘E. schistosa’’ are elevated to species status and provisionally referred to Enhydrina zweifeli. … Our findings have important implications for snake bite management in light of the medical importance of beaked sea snakes and the fact that the only sea snake anti-venom available is raised against Malaysian E. schistosa.

Have a look at this diagram:

Fig. 4. Bayesian multi-locus coalescent species tree. Asian and Australian Enhydrina schistosa lineages form separate and distantly-related clades (each with affinities to geographically proximate taxa). Nodes with Bayesian posterior probability >0.9 are indicated. Outgroup Hemiaspis damelii is not shown. (Scale bar = substitutions per site).

You can see the two populations, from Australia (top) and Southeast Asia (bottom), separated by numerous other species that look very different. And, if you look at just the Southeast Asian group, they cluster into two subgroups as well. Apparently this genetic divergence and grouping was not noticed by prior researcher dividing the snakes up into species and genera on the basis of morphology. Having said that, it is also true that the sea snakes are a bit dicy in their overall phylogeny, and are understudied. This, apparently, is being rectified.

There are other potential explanations for this pattern that should be considered, involving the genetics. It is possible to come up with a genetic tree that inaccurately represents the actual phylogeny of the species at hand. This study, however, used multiple methods and multiple DNA sites, involving both mitochondrial and nucleic DNA, so the species tree you see here is probably reasonably close to accurate, and the conclusion that Enhydrina schistosa consists of two groups that are not monophyletic is strong.

“This mixup could have been medically catastrophic, since the CSL sea snake antivenom is made using the venom from the Asian snake based on the assumption that it was the same species,” noted Bryan Fry, one of the study’s authors. “Luckily, the antivenom is not only very effective against the Australian new species but actually against all sea snakes since they all share a very stream-lined fish-specific venom.”

Wear a wet suit!


Ukuwela, K., de Silva, A., Mumpuni, ., Fry, B., Lee, M., & Sanders, K. (2012). Molecular evidence that the deadliest sea snake Enhydrina schistosa (Elapidae: Hydrophiinae) consists of two convergent species Molecular Phylogenetics and Evolution DOI: 10.1016/j.ympev.2012.09.031


Get the latest news about Sungudogo, the science fiction adventure story set in the Congo, which serves as a new Origin Story for the modern Skeptics Movement, HERE.

The Rocks Don't Lie (geology and flood myths)

The Rocks Don’t Lie: A Geologist Investigates Noah’s Flood by David Montgomery is new book on the Noachian flood. It is by a real life geologist and is not a creationist book. Might be a good gift for your annoying creationist relative.

Here is a write-up from the publisher:

In Tibet, geologist David R. Montgomery heard a local story about a great flood that bore a striking similarity to Noah’s Flood. Intrigued, Montgomery began investigating the world’s flood stories and—drawing from historic works by theologians, natural philosophers, and scientists—discovered the counterintuitive role Noah’s Flood played in the development of both geology and creationism. Steno, the grandfather of geology, even invoked the Flood in laying geology’s founding principles based on his observations of northern Italian landscapes. Centuries later, the founders of modern creationism based their irrational view of a global flood on a perceptive critique of geology. With an explorer’s eye and a refreshing approach to both faith and science, Montgomery takes readers on a journey across landscapes and cultures. In the process we discover the illusive nature of truth, whether viewed through the lens of science or religion, and how it changed through history and continues changing, even today.

… and here is a FREE COPY of a chapter of the book courtesy of the National Center for Science Education.

Oh, and in case you were wondering, no, it is not even close to true that “every culture has a flood myth.” But there is a falshood pertaining to that question: See “Every Culture Has A …

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Photo of the geology of Red Rock Canyon, Nevada by the author.

Interesting Intelligent Design and Evolution Spat Going On

Mike Haubrich, of Tangled Up in Blue Guy blog, has documented a discussion between a biologist, a commenter, and the Discovery Institute (a creationist “think” tank). No apes were harmed during this incident, but one of them may be rather embarrassed. It’s quite intresting, have a look: Cornelius Godsplains Science to a Scientist

Evolution Surrounded By Creationism? Arm Yourself with Books!

Suppose you are an intelligent, thoughtful person with a thirst for information, a desire to be challenged, and a tendency to not accept received knowledge at face value. You are embedded in a traditional Christian culture where most of your family, your child’s teachers and friends and those friends’ families, the people where you and your spouse work and most people in your social circles assume that Evolution is “only a theory” and should be taught, if at all, along side alternative theories such as that the earth is 6,000 years old and was created in seven days. But you don’t want that. You want your children to be educated using modern ideas, or at least, ideas that date to the mid to late nineteenth century and later, about how life works, where it comes from, and how it has changed over time both in terms of details (what was when and where) and process (how). But despite the fact that you are well educated and well read, you’ve not been exposed to that body of knowledge.

This will be a struggle, a fight even, against academic indolence, against strongly held opinions; An invasion across a sea separating two worlds … two world views. You might have to land on a beach somewhere. You hope, however, that this can be a surgical strike. You need to educate yourself on the basics of evolution. You need to find a way to talk your way out of confrontation should that happen. You need resources for your children. You may not realize it now, but you may also need training in Defense Against the Snark Arts, should you encounter paraprofessional creationists.

You need to arm yourself. With books.
Continue reading Evolution Surrounded By Creationism? Arm Yourself with Books!

Is the origin of life different from evolution?

I heard it said recently that “Evolution” and “Origin of life” are two separate issues. I know that this is a falsehood, and I’ll discuss in a moment how and why it is not true. But first, I checked around with a few people that I know and love, and found out that some of them assumed this was true. I think it is something that has been said enough times that if you are not personally engaged in the research or just don’t think about it enough, you can easily assume that this is what the experts say. But they don’t.
Continue reading Is the origin of life different from evolution?

Are The Miss USA Contestants more Pro Evolution than the United States Senate?

There’s been a fair amount of talk about the Miss USA interview question “should evolution be taught in schools,” and a fair amount of attention given to the answers provided by the contestants. For the most part, people have gotten mad at these women because they are both beautiful in a classic patriarchal-normative-way and are handmaidens or hobgoblins or whatever of the sexist system in which we live, and because they are all wrong about evolution and whether or not it should be taught in schools.

But, it is not so simple.

Continue reading Are The Miss USA Contestants more Pro Evolution than the United States Senate?

“If You Love Evolution, Tweet About It!” COE # 36

i-80e531b0d2456037296ea380dfc94a8a-_main_top_1872_Expression_F1142_327-thumb-300x300-65652.jpgWelcome to the Thirty Sixth Carnival of Evolution. The world of blog carnivals is in a state of flux and uncertainty these days, with the distinct possibility of a mass extinction just around the corner. One of the oldest, longest running, and most important carnivals, I and the Bird, issued its last issue only a few days ago, and the Keepers of the Carnival of Evolution themselves are said to be thinking about ways that this whole carnival thing can be made to work better. That could, I suppose, mean killing it and replacing it with something else. We are hopeful that this will not be something monstrous. Well, actually monstrous would be fine, I suppose, just highly unlikely to found a new species of scientific social networking.

With that thought in mind, I’d like you do to me a favor. If you are into evolution (which you probably are because you are reading this post) then help promote excellent evolution blogging. Do you have a facebook account? Good. Open up a selection of the following posts and if you like them or find them interesting, post them on your wall. Let your facebook friends see some of this interesting blogging. Do you tweet? Then tweet them! Oh, and go ahead and facebook-share and tweet this very carnival. Stumble, Digg, Reddit, Whatever. The idea is go get the word out that there is some interesting stuff to read, about evolution, on the intertubes. We want Evolution Blogging to be more linky and socially networked than other topics such as, well, creationism for example. This carnival is a pretty darn good listing of what has come out over the last few weeks across the blogosphere. So, your job as a lover of and promoter of evolution is to use this list of blog posts as a kind of todo list … working off this list, promote the posts.

I’ve taken a very straightforward approach to the carnival, which is my style; I let the posts speak for themselves. So, in the following listing you’ll see the title of each post and a brief excerpt. Click on the title to see the post. The categories into which I’ve divided the post make total sense and form a very good taxonomy of evolution blogging. For some of the posts. For others, the categories suck. It is not easy making categories for this sort of writing, as many of the posts are so darn multifarious, which is a good thing.

And now, the carnival:
Continue reading “If You Love Evolution, Tweet About It!” COE # 36

Universal remotes, evolution, sex, and sight

So Amanda had this TV. It had a remote. The remote sucked. It was broken. Then I moved in and with me came a universal remote. Lucky Amanda. I programmed the universal remote (a Radioshack 5 in 1) to handle the TV as well as a DVD player and a stereo. The remote handled everything. The old remotes hung around for a while occasionally being used, but then disappeared. Then we got a different DVD player and I had forgotten that the remote was a universal jobbie, so we just started using the remote for the DVD player Then we got an iPod cradle with speakers and a Roku. I purchased a Radio Shack switchbox during the Creation Science Fair at Har Mar in 2010 (some of you will remember that i did that, I was showing off a bit.) I ran the Roku to the TV via the switchbox. I ran the new DVD to the TV with the switch box. I got rid of the stereo (it was 99 percent broken). The switchbox was necessary because of the lack of connectors on the TV. While I was doing that, I also ran all of the audio outputs to the iPod cradle. And there was a Wii, so that ran through the switchbox to the TV as well as the iPod cradle.

So we had a TV remote that was originally a universal remote, but we forgot that it was a universal remote. We had a DVD remote. We had a Roku remote. We had a remote for the iPod cradle. We had a switchbox which was not have a remote but was kinda like a remote.

So…
Continue reading Universal remotes, evolution, sex, and sight

The Hopeful Monster Theory Returns Triumphant

Most evolutionary biologist have fully rejected the “hopeful monster theory” but it turns out they were wrong to do so.

Most mutations are deleterious, and are quickly weeded out of a population but in some cases not before they briefly cause hideous results that make everyone turn away in horror and disgust. But sometimes a hideous mutation can produce something new and amazing, something novel and wonderful, something never before seen and but which we could never imagine the world doing without. Here is an example:

Continue reading The Hopeful Monster Theory Returns Triumphant

How old is the earth, and how do we know?

How old is the earth?


Short answer: 4,540,000,00/H30 Earth-years, plus or minus 1%.

Long answer: We don’t know exactly because direct dating of the earliest material on the surface of the Earth will only tell use a minimum age; Prior to that, the Earth’s surface was probably molten, and even after that, it may be that the earliest non-molten material has been recycled into the planet’s interior by tectonic processes. Also, the earth is a big round ball of stuff that condensed into this shape from part of a large disk-shaped blob of stuff known as the Solar Nebula. When exactly, given this, did the Earth become the Earth? Since the process took millions of years, we can’t pinpoint the age of the Earth more exactly than a certain range.

What are the oldest rocks?

The oldest rock formations on Earth are between about 3.8 and 3.9 billion years old., but there are older bits of more ancient rocks that were incorporated into these early rocks, and they date to something closer to 4.4 billion years old. These and other early materials are dated primarily using a variety of parent-daughter radiometric techniques, with the most effective for this time period being a lead-lead system.

Since rock from the time of the Earth’s formation isn’t available (because it didn’t really exist or was gobbled up in the fiery beginnings of the big round ball) the preferred method of dating the Earth is to calculate the age of meteorites. The earliest meteorites essentially date the condensation of materials in the solar system into the planets, and thus, the date of these meteorites indicates the date of the early Earth. (The Earth existed prior to this condensation in the form of whatever parts of the early solar nebula would eventually condense into this particular planet, of course.)

Meteorites from other planets?

Some meteorites are known to be fragments of Mars, so the oldest dates among these can also verify the date of accretion of material into planets in our solar system.

Rocks from the moon have not been remelted or otherwise messed up by tectonic processes and therefore would provide an excellent estimate of the age of the Earth as well. Also, since there is no real weathering of rocks on the moon, methods other than parent-daughter decay can be used, such as Fission Track dating (the older a rock, the more cosmic rays pass through it, blasting tiny little tracks in the otherwise homogeneous matrix).

Zeroing in on the age of the earth

There are hundreds of published dates of various older materials, but the following table gives a reasonable summary of some of the more important dates, culled from various sources (see list of references below):

i-2416ee0f1d5ce9b6c98e162e41b0c09c-Age_Of_Earth_Data.jpg

If we chart this on a graph, we see one date that is much earlier than all the other dates, and a few that are younger.

i-9e501755c6fa4a6e7706e5935210cefe-Age_Of_Earth_Graph.jpg

The younger dates are simply of materials that we don’t think date the Earth’s formation, but that we know would post date it by not much. These dates verify the earlier cluster of dates that would correspond to the actual formation of the planet. The single earlier date is an obvious outlier.

Taking this series of dates, notice that the oldest (non-outlier) dates are about four and a half billion years old. As stated in the short answer.

Further information about the age of the Earth:

Dalrymple, G. Brent. 2001. The age of the Earth in the twentieth century: a problem (mostly) solved. Geological Society, London, Special Publications 2001, v. 190, p. 205-221. Click Here.

Dalrymple, G. Brent. 2006. How Old is the Earth: A Response to “Scientific” Creationism. The TalkOrigins Archive. Click Here.

Norman, M. D., Borg, L. E., Nyquist, L. E., and Bogard, D. D. (2003) Chronology, geochemistry, and petrology of a ferroan noritic anorthosite clast from Descartes breccia 67215: Clues to the age, origin, structure, and impact history of the lunar crust. Meteoritics and Planetary Science, vol 38, p. 645-661.

Stassen, Chris. 2005. The Age of the Earth. The TalkOrigins Archive. Click here.

Wikipedia, Teh. 2010. Age of the Earth. Click here.

What is meant by “mosaic evolution” and other matters

A discussion of misconceptions in evolution … about missing links, or great chains of being, or teleology (the idea that evolution is goal-directed) has got to be the most fun you can have with your pants on. Pursuant to this, let’s sharpen and clarify our evolutionary theory mojo by considering the concept of “mosaic evolution” … what is it, and what isn’t it?

Of course, the concept of mosaic evolution, meant to clarify how evolution works, is often itself misunderstood. From Wikipedia:
Continue reading What is meant by “mosaic evolution” and other matters