Jeff's Lunchbreak

The other night, we went out to eat with some friends. I forget why, but for whatever reason my daughter was going through, with our help, trying to think up a mammal for every letter of the alphabet (aardvark, bear, cat...) Well, for P she picked platypus, so when the game was all over, it got us to talking about them. And I foget exactly how the next part came up, but the guy I was talking to brought up that he couldn't see how they were related to other mammals, and that he really doubted the whole theory of evolution. I tell ya what - get a couple beers in me and then tell me you don't accept evolution, and just see what type of conversation gets going. Boy, was it fun. Unfortunately, I don't think I did much convincing. It had nothing to do with the beer, but a whole lot to do with the fact that discussions like that are basically my word vs. your word. Considering that I'm not a biologist or in any related field, and it makes my word worth that much less. So, I decided to write up an e-mail to send him, along with links to lots of sources backing it up. Once I got through with typing it, I figured that it made for a decent general introduction to evolution. Maybe at some point I'll clean it up and make a good essay out of it, but even in its rough e-mail form, I figure it makes for a decent blog entry. So, if you want to read it, go head below the fold.

I realize that for a blog entry, most people wouldn't consider 7 printed pages as "brief." However, for a concpet like evolution, for which there are countless journal articles published every month, and entire popular books devoted to a field as narrow as the evolution of language in a single lineage, 7 pages does seem fairly short. Also, while I would normally include verbatim copies of e-mails in block quotes, this is long enough that I figured I'd make it easier to read by posting it without a block quote.

Disclaimer: I am not a biologist.

[start of e-mail]

That was a good discussion the other night at Buffalo Wild Wings, but it's a pretty difficult topic to address by just talking about. I figured I'd send some follow up information so I could list sources, and you don't have to take my word for some of the things I was saying.

First, I guess I should address what is actually meant by "evolution." First, there's the idea of common descent with modification - the idea, for example, that a house cat and a lion both have a common ancestor, and that over many, many generations, one lineage evolved into Felix, while the other evolved into the king of the beasts. Then, there are theories as to how that happened. Natural selection, the most well known, and possibly the main driving factor, is one of those theories - explaining how certain mutations propagate while others are weeded out. There are also other theories, including sexual selection and genetic drift, not to mention theories on how speciation occurs, from allopatric to peripatric to parapatric to sympatric. And there are still further theories, like Lamarckian evolution, which have been discredited. It's important to separate common descent and proposed phylogenies (family trees) from the theories describing the mechanisms of evolution. It's a bit like gravity - separating the observation that all matter is attracted to other matter, from theories like relativity which describe the mechanisms of how that happens.

Next, I guess I should address how we can be confident about evolution in general. I'm going to cheat on that one and recycle something I already wrote. Thanks to my website, I got into an e-mail discussion with a guy that rejected evolution based on a literal interpretation of Genesis. We went back and forth a little bit, and I ended up expanding one of my responses to him into a full blown essay, which I've attached to this e-mail.

[06-Confidence in Historical Knowledge.2008-03-28.pdf - the essay attached to that e-mail]

You were also asking about our ancestors - what fossil evidence there was. I guess this is a good time to bring up another point - what fossils should we expect to find? Fossilization is a pretty rare event. When most organisms die, they get eaten and decomposed, and there aren't any recognizable remains. It takes a special set of circumstances for remains to get covered up quickly enough that they don't decompose, but gently enough that they don't get dashed to pieces, and it's even rarer still for this to happen to a nearly complete skeleton/tree/whatever type of organism, and not just bits and pieces. It's usually some form of sediment that gets deposited over the carcass, which then hardens into sedimentary rock, while the remains of the organism are replaced by minerals. So, the best places to find fossils are ancient lakes, swamps, riverbeds, seas - places like that. In places like jungles, where there are lots of animals and scavengers to eat the remains of dead animals, you expect even fewer fossils to form. Then, even if just the right circumstances existed for a fossil to form, we need to be lucky enough to find it. Remember, it's usually sediment deposition that helps form fossils. Depending on how long that environment was stable, those depositions can get pretty thick - just look at the chalk cliffs in Dover, England. So, after fossils were formed, we usually rely on some type of erosion to come back and expose the fossils. And then, on top of all that, somebody needs to be there to find the fossil once it is exposed, before erosion carries on further and destroys the fossil altogether. Given all that, you wouldn't expect to find fossils for every species that has ever existed.

The living great apes besides us all live in jungles. As per the above paragraph, you don't expect to find many fossils of them, or their jungle living ancestors. At some point, as the jungles in Africa shrank to be replaced by savannah, our ancestors moved to that new habitat. Since that habitat is more conducive to fossilization, you would expect to find more fossils for our ancestors than the other great apes, and in fact, we do. After a little Googling, I found these sites. They have nice graphics showing some of the skulls that have been found, and fitting them into speculative family trees. Using the word "speculative" here should not call into question the concept of common descent. It's simply that there are so many species, and the phylogeny is so complex, that it's hard to work out the exact details.

http://evolution.berkeley.edu/evosite/evo101/IIE2cHumanevop2.shtml (drawings - not photos - but easy to follow)
http://www.mc.maricopa.edu/dept/d10/asb/anthro2003/origins/hominid_journey/timeline.html (photos of skulls on a timeline)
http://primatediaries.blogspot.com/2007/08/apparently-not-very-long.html (more detailed drawings, easier to follow than photo version)

Let's see, we also discussed genetic mutation, which is really the raw material for evolution that natural selection acts upon. Here's the quick primer - to reproduce, organisms must replicate their DNA. We know this replication process isn't perfect, and that mutations occur on a regular basis, so that there will invariably be offspring with different genetic makeups than their ancestors. Since organisms have more offspring than the environment can support (in the case of many egg laying animals - hundreds of times more per generation), it just stands to reason that the best adapted organisms will survive more often, and go on to produce even more offspring. Considering how many individual animals have been alive throughout history, and how many times they've reproduced, there have been plenty of chances for beneficial mutations to occur. That's evolution in a nutshell.

I know one of the things we discussed was mutation rates, and how common they actually were. So, here's a link to a short page, citing two studies, listing those rates. In non-coding regions of DNA, humans have between 64-175 mutations per generation. In coding regions, this rate is a lot lower, down to about 1.6 per generation in humans. You'd expect the coding regions to have a much lower mutation rate, because harmful mutations there would most likely result in embryos that never made it to birth. They get weeded out very quickly.
http://www.talkorigins.org/indexcc/CB/CB100.html

One of the best brief explanations I've seen describing how DNA provides very striking evidence in favor of common descent was actually a comment on a blog. It even cites journal articles for sources, if you really want to research it more. The comment deals mostly with the genetics of chimps and humans. Note that his comment is addressed to a Mr. Lewis which most definitely is not me. This really is a very good explanation, and if you don't follow any of the other links in this e-mail, I'd recommend following this one.
http://scienceblogs.com/pharyngula/2006/11/handing_out_a_little_rope.php#c273929

Once last thing to bring up on genetics is a concept known as plagiarized errors. It seems that well over 3/4 of our genetic material is non-coding - it doesn't create proteins. Some of that may be important for spacing or other functions, but most of it really does seem to be worthless - just added baggage that gets copied every time a cell replicates. You can have mutations in those regions with practically no effect on the fitness of the organism - explaining the results of an above paragraph where mutations in our non-coding regions are so high. Outside of common descent, there's really no reason to expect that different species would have similar DNA sequences in the non-coding regions.

Furthermore, sometimes functional genes can be destroyed through genetic mutations. Since there really isn't any mechanism in our cells to clean up these types of mutations, the broken genes tend to persist. These regions, recognizable as broken versions of once functioning genes, are known as pseudogenes. One of the examples in the article I'm about to link to is the gene responsible for making ascorbic acid (Vitamin C), L-gulono-gamma-lactone oxidase, or GLO. Pretty much all mammals have this gene, allowing them to synthesize their own ascorbic acid. The only known exceptions are guinea pigs and primates. (The most likely explanation for how this mutation could become widespread is that when it happened, those animals were getting so much ascorbic acid through their diet, that losing the ability to synthesize it didn't harm those individuals, so natural selection didn't weed them out. It's even possible that by conserving energy by not producing that protein, they might have had a slight advantage.) Primates and guinea pigs are only distantly related as far as mammals go, so it seems likley that our common ancestor had a functioning copy of GLO, and the guinea pig and primate lineages had independent mutations that caused the loss of function of the gene. Scientists did go looking for those pseudogenes. First of all, they did find them in both guinea pigs and primates, which is one more bit of evidence for evolution (why would we have pseudogenes if they weren't inherited from an ancestor with a functioning copy of the gene). Second, they found that the mutation that crippled GLO in guinea pigs and primates was a different mutation, and that primates all shared the same mutation - another finding which is to be expected from common descent.
http://www.talkorigins.org/faqs/molgen/

With all this talk of mutation, I guess I should give at least one example of an observed genetic mutation producing a new function. A species of bacteria had a mutation which allowed it to digest nylon:
http://www.nmsr.org/nylon.htm

And for one more example of observed evolution through mutation, just consider bacterial resistance to antibiotics:
http://aac.asm.org/cgi/content/full/46/2/267

To me, personally, our kinship to the other apes never gave me much of a problem. I mean, just look at this photo, with the head blurred out to emphasize the similarities in body plan:
http://www.jefflewis.net/graphics/my_family_album_edited_reduced.jpg

or here, with the head visible:
http://www.jefflewis.net/graphics/my_family_album.jpg

There doesn't appear to be a whole lot of difference between us and chimps, so it seems pretty easy to accept that we had a common ancestor. To me, the really interesting evolutionary stories are the ones where animals have evolved to survive in completely new environments - such as the transition from fish to tetrapods, land mammals to whales, land mammals to bats, non-avian dinosaurs to birds, etc. Okay, since this e-mails getting long enough as is, I'll just put some links for those:

Fish to Tetrapod:
http://www.pbs.org/wgbh/evolution/library/03/4/l_034_03.html
http://en.wikipedia.org/wiki/Tiktaalik
(I've got a good book about this, too, if you want to borrow it: http://www.amazon.com/At-Waters-Edge-Fingers-Whales/dp/0684856239) [note to blog readers - unless you live in Wichita Falls, no, I'm not going to loan you this book. Try your library.]

Mesonychid to Whale
http://www.edwardtbabinski.us/babinski/whale_evolution.html
(That same book from above covers this transition, as well.)

Bat Evolution:
http://scienceblogs.com/loom/2008/02/13/a_hairy_archaeopteryx.php

Non-avian Dinosaurs to Birds:
http://en.wikipedia.org/wiki/Origin_of_birds

Okay, getting away from all that theory, I just wanted to clarify a couple comments I made while we were talking. First, when we were discussing monotremes, I kind of pulled a number out of my ass (I told you so at the time), guessing that our last common ancestor with monotremes was probably on the order of around 100 million years ago. Well, I googled it, and found that my guess was short by about 60-80 million years. Somebody did a molecular study and come up with the following:
"The distance data support the view that the echidna and platypus lineages diverged from their last common ancestor at least 50 to 57 Ma (million years ago) and that monotremes diverged from marsupials and eutherian mammals about 163 to 186 Ma."
http://www.springerlink.com/content/j528128pt8546711/

160 million years is a long time - the end of the Cretaceous, when the last of the non-avian dinosaurs went extinct, was only 65 million years ago. That's plenty of time to allow for the evolution of a few novel features such as a poisonous leg barb, or a leathery bill.

The other one I'd like to clarify is that quote I was trying to remember. I found it online, "You must keep an open mind, but not so open that your brains fall out." It was actually made by a NASA engineer, James Oberg. While looking for it, I came across a very interesting article. It's not exactly related to evolution, but it is related to scientific thinking in general. It's written by the editor of a medical journal, explaining how they try to weed out crackpot pseudo-scientific papers from legitimate theories on the fringes of science. I thought you might find it interesting (one thing that caught my eye, which I'll have to research more, is that even though the mechanisms aren't understood, "the weight of the evidence appears to support the clinical efficacy of acustimulation for some indications.")
http://www.anesthesia-analgesia.org/cgi/content/full/104/2/247

Last thing, a couple suggestions for good places to browse through to learn a bit more about evolution. The first is a site that offers a good overview of evolution, but also devotes a lot of its pages to addressing many popular misconceptions associated with it (mostly those invented by people holding to a literal interpretation of Genesis):
http://www.talkorigins.org/

Berkeley's evolution site is also pretty good. It's more general, and doesn't spend as much time specifically dispelling myths and misconceptions:
http://evolution.berkeley.edu/

Okay, I know this e-mail got kind of long, but for one, evolution's been a subject that's really interested me for a while, so I tend to read up on it when I can. For another, to support the point I was trying to get across the other night, there really is overwhelming evidence supporting evolution, kind of like heliocentric theory, and this e-mail isn't even beginning to scratch the surface of that evidence.

So, if you've got any points, I'd be happy to discuss them. I don't think I'll have the time to write another e-mai this long, but a good discussion over a case of beer wouldn't be bad.

[end of e-mail]

Update 2008-03-31: I made a few changes to this entry, but nothing that significantly changed the meaning. Also, if you read the intro paragraph, it states that I wrote up an e-mail response to the guy, but not that I'd actually sent it. In fact, when I first posted the blog entry, I hadn't actually e-mailed the response - I was waiting on getting the guy's e-mail address. Why do I bring this up now? Well, the slight changes I made to this entry were incorporated into the e-mail before I sent it, so this modified entry is a verbatim copy of the e-mail that was actually sent.

Posted by Jeff on A, Mar 28 | Permalink | Comments (43) | TrackBacks (0)

I've added a new recipe for Easter bread to my How To page. This is the recipe my mom made while I was growing up and passed on to me. Other than that, there's no deep family significance - I think she got it out of a cookbook, which got it from a convent in Pittsburgh. And I realize it's a little late for this year, but honestly, it was while my daughter and I were making the bread this past weekend that the thought occured to me to add it to this site.

Posted by Jeff on A, Mar 27 | Permalink | Comments (41) | TrackBacks (0)

I will never again get a loan through Wells Fargo (at least not until all the other banks have similarly pissed me off and I have nowhere else to go).

When my wife divorced her ex-husband, she got full ownership of the house. The divorce papers stated so. She and her ex-husband signed a Special Warranty Deed, stating in detail that the house was hers, along with the loan, and all other monies (escrows, deposits) associated with the house. The deed was signed by a notary, and filed at the county courthouse. Everything was nice and official and legal.

Because of the fees that Wells Fargo would have charged to change the loan to her name, and because her ex-husband was renting and having the loan in his name wasn't doing him any harm, my wife didn't make it a top priority to get the loan in her name. However, when we decided to move last summer and put the house up on the market, we decided that we ought to get it done so that there weren't any problems when it came time to close on the house. Well, my wife talked to one of the loan officers at Wells Fargo, showed him the Special Warranty Deed, and he told her not to worry about it. He said the deed was official enough, and there was no reason to pay the fees since we were just going to to be selling the house, anyway. We thought we were in good shape, and figured everything would go smoothly when we finally sold the house. We were wrong.

Last month we finally did sell the house (to our relief, what with the housing market the way it is, and having to pay two mortgages), so my wife called Wells Fargo to make sure everything was okay. The loan officer she'd talked to before was gone - up and moved to a different state. Now, every time she tried to talk to somebody about the loan, she was told that since her name wasn't on it, they couldn't talk to her about it. They said we needed to get a Power of Attorney for the loan from her ex-husband. Well, we tried that, but he wasn't exactly very cooperative. My wife tried to tell them about the Special Warranty Deed. She offered to fax it to our local office, but the lady there told her that she wasn't even going to read it, that it would be a waste of their time since it wasn't the power of attorney letter. She even told my wife that maybe this was something she should have taken care of before trying to close on the house (remember - the previous Wells Fargo loan officer we talked to was the one that told us not to worry about changing the name on the loan).

My wife tried calling the national office, and didn't have much better luck there. Finally, after several calls with nobody wanting to even give my wife the time of day, at the end of the week we faxed them the Special Warranty Deed, along with a letter explaining why it should have been all they needed. The next week, when my wife called to check on the loan, they had no record of receiving the deed. But luckily, she had gotten someone helpful that time. He said he wasn't in the right department to look over legal paperwork, but to go ahead and fax it to him personally, and he'd hand deliver it to the legal department to make sure it got there. We were supposed to give the legal department 4 days to look it over. Well, this guy did get the document to the legal department like he'd said he would. But by this point, my wife had been going back and forth with the bank for a few weeks, and that fourth day we were supposed to give the legal department was also the day we were supposed to sign the paperwork to sell the house.

So, every day my wife called customer service to see if the legal department had looked it over, yet. I mean, it's pretty cut and dried, not much interpretation to do on it. Every day they told her the legal department had x many days left. So, finally, on the fourth day, the day we were supposed to close on the house, the legal department still hadn't looked it over. After a half an hour of "discussing," the guy she was talking to said he'd go grab the fax and look at it himself. When he got back on the phone, he said something to the effect of, "You know what, this document gives you full control over the loan. I'll go ahead and put your name on it." Nearly a month of arguing with customer service people until that moment. Argh.

At least we got it taken care of in time, we sold the house without a hitch, and all the tax/escrow checks got made out to my wife. Still, I was anything but impressed with the customer service at Wells Fargo. We did get two useful people, but the majority were incompetent, and one was just downright rude.

Well, once we started telling people our Wells Fargo story, they began telling us their horror stories, too. So, I'll add them here just to pile it on.

One lady recently lost her husband to cancer. The mortgage was in both of their names, so she called Wells Fargo to get the loan changed into her name only. They told her she needed a power of attorney letter from him. She said, "He's dead! What do you want me to do, go dig him up?" They also told her that now that the conditions of the loan had changed and he was no longer going to be on it, they could call the loan in. Assholes. Telling a grieving widow that on top of everything else she was going through, she might have to refinance her house, too. And just to put it in perspective, he was retired, and his pension would continue to give her the same payments she'd been receiving every month. Plus, she worked. Her income wasn't being changed at all.

The same month her husband died, this woman made a small mistake in the check for her mortgage payment. She'd made the exact same mortgage payment for years, a little higher than the minimum payment to get a little more of the principal paid off, and rounded off to an even number. This month, she wrote it down correctly in the part where you spell out the amount, but forgot the last few zeros in the part where you just write the numbers - it was 100 times less than it should have been. Well, instead of noticing the discrepancy between this check and all her other checks, or even noticing the discrepancy on the check itself between two different amounts specified, they cashed it for the smaller amount, didn't tell her anything, and charged her a penalty for not paying enough. When she noticed it the next month and called about it, they said they go by what's written in the numeral section, not the handwritten section. They didn't even refund the penalty.

Another person we know faced a similar threat when she got divorced. The loan was getting changed to her name only, and Wells Fargo threatened with calling in the loan on her, too, since the household monthly income was being changed. She also had a problem with one of her payments. Her grandmother was helping her out, and went by the bank to pay that month for her. The bank refused to take the payment from the grandmother since the check wasn't in our friend's name.

Just one note - I've never had any problems with the tellers at the branch I go to. They're all very friendly, and have been helpful in the past. It's their loan department in particular that has been such a pain.

Anyway, after our hassle with Wells Fargo, and hearing the hassles they've put our friends through, I very nearly refinanced the mortgage on our current house with another bank, but I'm not going to cut off my nose to spite my face. As much as I hate to keep on giving them interest payments, I'm not ready to pay a few thousand out of pocket to refinance with someone else. I'll just have to content myself with venting about it here, and vowing to never get another loan with them.

Small Update 2008-03-28: I replaced the original image of a Wells Fargo Stagecoach with an old photo of a stagecoach robbery. Yes, I'm still that bitter.

Posted by Jeff on A, Mar 21 | Permalink | Comments (46) | TrackBacks (0)

There's a new movie coming out called "Expelled," that maybe I'll get aruond to blogging about in more detail later (or maybe not). Its about the supposed close mindedness of the scientific community concerning Intelligent Design, how ID advocates have been unfairly discriminated against because of their views (I'm sure anyone reading this can guess how I feel about those two things), and supposedly even tries to link evolution to the Holocaust (actually, that last one does piss me off - it's an insult to all the people that suffered and died in that tragedy to use their memory for such a dishonest political purpose. Have they no shame?). Anyway, the biologist, blogger, and outspoken critic of ID/creationism, PZ Myers was interviewed for the movie (under false pretenses), and recently tried to attend one of the screenings. There was an online registration you had to complete before going, which he did. Well apparently, the producers had left specific instructions not to let Myers in, he was recognized him while he waiting in line, and was told to leave. Just imagine - a movie all about supposed suppression of free expression, asking a person they'd interviewed, to leave so that he couldn't see what they had to say or how he was being represented in their film. Oh, the irony. But that's not even the worst part. Myers was there with a few friends and family, one of whom was very notorious, who the security didn't recognize and was allowed to enter. Who, you ask. Well, go read Pharyngula to find out.

Posted by Jeff on A, Mar 21 | Permalink | Comments (42) | TrackBacks (0)

Here's a short entry for today. I'm probably one of the last people on the Internet to find this, but I thought I'd put it here on my blog for those people I know that don't frequent nerd sites very often (by find, I mean actually going to the site and reading through it - I'd already seen a few of the comics on other blogs before).

To get to the point, there's a very good web comic called xkcd (which apparently doesn't stand for anything in particular), which according to the site itself, is all about "romance, sarcasm, math, and language." He probably should have mentioned science, too. It's pretty funny, with a few random, interesting sketches thrown in, as well. I've put a handful of my favorites below the fold to give a taste of what it has, or you could just head on over there to check it out yourself. Don't forget to let your mouse hover over the images to read his comments.

One note before you click through to below the fold - one comic drops the f-bomb, so you've been warned. Also, before you go to his site, here's the warning he has, "this comic occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors)."

I apologize for the pixellation - some of the comics are wider than my blog's format allows, and rather than resizing the right way (saving the pictures, resampling them, and uploading them to my site), I took the easy way out, and simply changed their height and width properties in the img tag.

Donner

http://xkcd.com/30

Apple Jacks

http://xkcd.com/38

Love

http://xkcd.com/44

Secret Worlds

http://xkcd.com/52

Why Do You Love Me?

http://xkcd.com/58

National Language

http://xkcd.com/84

Paths

http://xkcd.com/85

Duty Calls

http://xkcd.com/386

Posted by Jeff on A, Mar 14 | Permalink | Comments (42) | TrackBacks (0)

A very small update for today, but an update, nonetheless. About a year ago, when I decided to sell my RX-7, I made a note of it on my RX-7 page. However, when I did sell the car, I forgot to update that page to say so. So, I've removed the note about the car being for sale, and added a paragraph explaining that I sold it, why I sold it, and that I still like it.

Posted by Jeff on A, Mar 14 | Permalink | Comments (40) | TrackBacks (0)

The full title of this book is At the Water's Edge : Fish with Fingers, Whales with Legs, and How Life Came Ashore but Then Went Back to Sea. It was written by Carl Zimmer, and as the long title suggests, is all about those two dramatic transitions of life evolving into such distinct environments. This book was great - one of the best non-fiction books I've read in a while. It was just the right blend of story telling, concepts, and evidence, and made for a very compelling read. In fact, I think I finished it in less than a week.

When I reviewed another book by Zimmer, the Smithsonian Intimate Guide to Human Origins, I commented that it wasn't very in depth. At only 176 pages, much of them filled with photos and illustrations, it was a little light on commentary. At the Water's Edge is very different in this regard. It's 304 pages, filled with small print, with only enough diagrams as are needed to illustrate a few key points. It's not a tome, by any means, but it certainly provides Zimmer with enough space to do this subject justice.

The book is divided into basically two halves - the first dealing with the transition from lobe finned fish to early tetrapods, and the second half dealing with the transition from mesonychids to dolphins and whales. As would be expected, both halves deal with the specifics of each of those cases - transitional forms that have been discovered, environmental pressures that would drive the transition, etc. However, mixed throughout the entire book are also sections on general theory. There's a nice section on development in the beginning, covering such topics as Hox genes and non-genetic factors; he describes exaptation; there's another section on cladistics; as well as sections on many other concepts related to evolution.

I learned quite a bit by reading this book. Even though I was already familiar with much of the general theory, Zimmer presented it in ways that made me think of things differently. He also introduced a few concepts, such as the evolutionary "quit point," that I hadn't thought of much before. Still, where I learned the most was in those specifics of the transitional forms between fish and tetrapods, and land mammals and whales.

I'll give one example of something very interesting I learned from this book. (In fact, this was the very first passage of the book that I read, when I first got it and was just thumbing through to see what it was like.) At some point, our ancestors must have developed lungs to breathe air, obviously. When we look at the world around us, most fish today cannot breathe atmospheric air - they rely on their gills to get oxygen from water, but also have organs similar to lungs called swim bladders, which they use to regulate their buoyancy. From that observation, you may be tempted to think that lungs are a modified swim bladder, which perhaps evolved to allow fish to survive in swamps or other oxygen poor environments. After all, what need would an ocean going fish have of lungs? I know that's what I had thought, but as it turns out, it's almost certainly wrong.

When you look at a phylogenetic tree of fish & tetrapods (such as the one on this page, which also has an excellent discussion on this topic), it becomes apparent that it's only one group of fish that has true swim bladders, while a few closely related groups have bladders that are open to air exchange, and most groups have lungs. It seems highly unlikely that swim bladders would have independently evolved into lungs in so many lineages, so the simplest explanation is that lungs came first, and later evolved into swim bladders in that one group. The thing is, that one group, the teleosts, or ray-finned fish, has become the most successful group of vertebrates on the planet, with over 20,000 extant species. Their success has biased our perception of what is normal concerning swim bladders vs. lungs.

After studying the phylogenetic tree, a person may still be left wondering what use lungs would be to fish. As it turns out, they can be quite useful. Obviously, there are all the living fish that have lungs (such as, as its name implies, the lungfish), or ray finned fish that have independently evolved means of breathing atmospheric oxygen (such as those staples of pet stores, bettas). Oxygen supplies are not as consistent in water as in the air, so it could be very advantageous for a fish to be able to get oxygen that way. Even in the ocean, oxygen levels can vary. There's another reason that I'd never even considered, which has to do with the circulatory system of a fish.

A fish's blood is pumped from the heart, to the gills where it picks up oxygen, through the body, and then back to the heart again. By the time the blood gets back to the heart, the other tissues have already absorbed most of the oxygen and there's not much left for the heart. So perhaps, lungs were a way for fish to supplement their oxygen intake, and be sure that the heart didn't become oxygen starved (more info can be found on this in an article by Zimmer in Natural History magazine, available online).

Finally, one may ask, if lungs were so useful to early fish, why would the teleosts have lost them? One explanation Zimmer offered, is that perhaps once airborn predators, like pteranodons, evolved, coming to the surface to grab a gulp of air became riskier behavior, and was no longer worth it. Perhaps it was because buoyancy control was that useful. There's also the fact that some teleosts have evolved a new way to keep their heart oxygenated - with coronary arteries that run from the gills straight to the heart. Maybe it was all these factors combined that caused teleosts to lose the ability to breath with their lungs/swim bladders, or perhaps some other reason we haven't thought of, yet. (Just as a note, sharks and rays diverged from bony fish around 420 million years ago. Sharks and rays have neither bladders nor lungs, indicating that the organs developed after that split. You'll also notice that means a gold fish is more related to us mammals than to sharks.)

In that introductory paragraph, I mentioned story telling. Zimmer does not simply present the theories and evidence for these transitions. He talks about the people involved in the discoveries, going all the way back to Sir Richard Owen (the man who coined the term dinosaur) all the way up to meeting Ted Daeschler on a rainy afternoon in Pennsylvania. He describes the personalities involved, and their contributions to our current understanding. You can see how these theories have been refined over time.

One last note, regarding the wonders of the electronic age. Carl Zimmer has a blog, The Loom, where he describes new scientific findings, or links to articles he's written that are being published elsewhere. It's one of the few blogs I'm sure to check at least weekly, since his articles are so interesting. Just recently, he's written three entries that complement this book very well: Whales: From So Humble A Beginning..., Return to the Dawn of Whales: Cousins Versus Grandparents, and On the Path Towards Leviathan.

I found this book to be extremely interesting, and very enjoyable to read. I would recommend it to anybody with the slightest interest in the history of life on this planet.

Edited 2011-06-28: Modified link to phylogenetic tree of fish & tetrapods to point to the WayBack Machine, since the original link was broken.

Posted by Jeff on A, Mar 7 | Permalink | Comments (42) | TrackBacks (0)

A very short entry for today (hopefully I'll get a real entry out later this week). Today is the day for the Texas Assessment of Knowledge and Skills test, better known as the TAKS test. These tests are very high stakes for elementary school students - the children must pass this one test today in order to graduate to the next grade level. If they bomb it, they're doomed to repeat their grade, no matter how good they might do in school otherwise. (update 2008-03-05- Actually, the students get 3 chances to pass.) My daughter and one of her cousins are taking the test this year, and they're both fretting over it. 3rd graders, almost as nervous as college students at finals time. There's also the major concern that with the importance of this single test, teachers focus on teaching their students how to do well on it, instead of trying to give them a more general quality education.

Anyway, I found a good blog from a Texas teacher discussing this, Education in Texas. Take a look specifically at this entry,
Time For Some State Sponsored Torture of 8 Year Olds. He also has a few others dealing with this issue.

Posted by Jeff on A, Mar 5 | Permalink | Comments (40) | TrackBacks (0)