I think it's time we started being serious about the limitations of the RNA world as a possible explanation for the origin of life. It's simply not possible to imagine a scenario where the first catalysts are RNA molecules because that requires a primordial soups full of nucleosides and sugar molecules. It requires the spontaneous synthesis of nucleotides and their polymerization.
That ain't happening.
You can salvage the RNA world by postulating that it arose AFTER primitive metabolic pathways were established using peptide catalysts but that's the best you can do. There's a nice article in The Scientist that describes the problem [RNA World 2.0].
Here's a teaser ....
The RNA world, first posited by Francis Crick1 and others in the late 1960s, remains an attractive hypothesis. Many of the chemical hurdles that once challenged the laboratory synthesis of the molecule under presumed primordial conditions are being overcome, and in vitro evolution experiments are yielding RNA molecules that perform numerous functions, including copying themselves or other RNAs. "I don’t think there can be much doubt that RNA was a major central player as both a catalyst and an early replicator," says Nick Lane, a biochemist at the University College London whose research falls under the “metabolism first” label. "So the RNA world is absolutely correct, as far as I’m concerned, in that."
But the notion that RNA, on its own, spontaneously assembled and evolved on early Earth has fallen out of favor. More likely, whatever conditions spawned compounds as complex as nucleotides also generated other organics, perhaps early forms of modern amino acids and fatty acids, the constituent parts of proteins and membranes. "I’m not sure how many people anymore believe in a pure RNA world. I certainly don’t," says Lane. "I think the field has drifted away from that, and there’s now an acknowledgment it had to be ‘dirty.’ "
Changing Ideas About The Origin Of Life
Was the Origin of Life a Lucky Accident?
Monday's Molecule #231 [Monday's Molecule #231] was the Shine-Delgarno sequence found a few nucleotides upstream of the initiation codon in many bacterial mRNAs. It interacts (base pairs) with a sequence on the 3′ end of 16S RNA to help form the translation initiation complex. This means that bacteria can have polycistronic mRNAs (from operons) and internal translation initiation. The winners were Keith Conover and Nevraj Kejiou. That's two weeks in a row that an undergraduate from the University of Toronto has won. I will be taking them to lunch. I encourage undergraduates from far, far away to hurry up and send in an answer to this week's molecule!
This week's molecule (left) is covalently bound to the lysine side chain of a protein. It exists in two distinct configurations that can be interconverted by a well-known chemical reaction. Name the two different configurations (common names only) and explain the significance of the reaction.
Email your answer to me at: Monday's Molecule #232. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.
There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)
Saturday night was the night when most people in North American turned their clocks forward one hour for "Daylight Saving Time."1 TV, radios, and newspapers are whining about the fact that everyone was going to lose an hour's sleep. Some of the comments on my radio station advise people to avoid driving today (Monday) because you might be suffering from sleep deprivation.
This all seems very strange to me. Is it true that most people are so unfamiliar with traveling across time zones that turning your clock back one hour is a really big deal?
And what's this about losing one hour's sleep? When I got out of bed on Sunday morning it was about one hour later (on the clock) than the time I usually wake up on Sunday morning. I didn't lose an hour's sleep. The only people who lost an hour's sleep on Saturday night are those who wake up every Sunday morning to an alarm clock. Are you one of those people?
It's a little bit different on Monday morning when, I imagine, most people have to wake up to an alarm clock in order to get to work. I'm not one of those people. However, even on Sunday night the only way you lose an hour's sleep is if you went to bed an hour later than normal.
Somewhere along the way I have lost an hour of my day but it's not going to come out of sleep time. That would be silly. If I ever feel sleep deprived I'll just go to bed earlier.
How about the rest of you? Do you really give up an hour of sleep in the days following the shift to Daylight Savings Time?
More accurately known as "Daylight Shifting Time."
Later on today I'm giving a talk at Western University (London, Ontario, Canada)1 The subject is blogging.
I realized while preparing my talk that there were lots of things I didn't know for sure so here are some questions that you may be able to help with.
Most popular biology blogs
I don't know for sure which biology blogs are the most popular. I'm pretty sure that Pharyngula is still on top with respect to the number of views per day and I'm pretty sure that Why Evolution Is True is in the top ten but what about others? Do any of you know?
Best biology blogs
The best blogs aren't necessarily the most popular. I have my own opinion about the best blogs but my fear is that I've missed some blogs that I should be reading. What do you think? What are the best biology blogs?
Why do you read and comment?
I've talked to a lot of bloggers so I'm pretty sure I have a good idea about why we write blogs. But I realized that I was much less sure about why people read blogs and why people comment on blogs. What do you get out of reading blogs and why do you post comments? Do you think all scientists and science students should read the science blogs? (I don't.)
Have blogs changed anything?
Have blogs had much of an impact on science? I can think of a few examples such as the Arsenic Affair and the ENCODE Publicity Hype Fiasco where bloggers had an impact but I'm not sure these are significant in the log run. Is blogging just another kind of social interaction that really doesn't change the way science is done?
1. Formerly the University of Western Ontario. The talk is in the North Campus Building room 114 at 11:30 am.
THEME:
Transcription
The Journal of Biological Chemistry (JBC) publishes a little booklet of the "best of jbc." The latest copy arrived in the mail a few days ago and it alerted me to a paper published one year ago on the structure of Escherichia coli RNA polymerase σ70 holoenzyme (Murikami, 2013).1
The control of transcription initiation is a very important topic in biochemistry and molecular biology and the events in E. coli are the model for transcription initiation in all other species. We know more about RNA polymerase and promoter sites in E. coli than in any other species.
Monday's Molecule #230 (Jan. 27, 2014) [Monday's Molecule #230] was 2-carboxy-3-ketoarabinitol 1,5-bisphosphate. It's an intermediate in the reaction catalyzed by ribulose 1,5-bisphosphate carboxylase-osygenase (Rubisco), the key enzyme in the Carvin cycle. This is the molecule created by adding CO2 to the 2-carbon atom of ribulose 1,5-bisphosphate. The winners were Bill Gunn closely followed by the first correct answer from an undergraduate, Ariel Gershon. Ariel is a student at the University of Toronto so it looks like I'm going to have to buy a lunch.
This week's molecule (below) is a sequence. Name the sequence in red and briefly describe it's function.
Email your answer to me at: Monday's Molecule #231. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.
There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)
This month's Carnival of Evolution is hosted by a BIOCHEMIST (yeah!) named "Lab Rat" (S.E. Gould) at Lab Rat. Read it at 69th Carnival of Evolution: Darwin’s Day Edition.
Welcome to the 69th edition of the Carnival of Evolution! As February 12th was Darwin’s birthday, this is a Darwin’s Day carnival edition. To start with there’s a celebration of all things Darwinian at Synthetic Daisies, and a letter to the man himself for his 205th birthday.
The next Carnival of Evolution will be at ????
If you want to host a Carnival of Evolution please contact Bjørn Østman. Bjørn is always looking for someone to host the Carnival of Evolution. He would prefer someone who has not hosted before but repeat hosts are more than welcome right now! Bjørn is threatening to name YOU as host even if you don't volunteer! Contact him at the Carnival of Evolution blog. You can send articles directly to him or you can submit your articles at Carnival of Evolution although you now have to register to post a submission. Please alert Bjørn or the upcoming host if you see an article that should be included in next month's. You don't have to be the author to nominate a post.
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I forgot to post a link to last month's Carnival of Evolution. It was hosted by a computational biologist who posts at Byte Size Biology. Read it at Carnival of Evolution, February 2014 Edition.
Wow, I haven’t posted anything in quite a while. Things are busy outside blogoland. But committing this blog to the February edition of the Carnival of Evolution just made me do it, so here goes. We’ll do this by scales, bottom up.
The next Carnival of Evolution (#70, April, 2014) will be at some unknown place.
If you want to host a Carnival of Evolution please contact Bjørn Østman. Bjørn is always looking for someone to host the Carnival of Evolution. He would prefer someone who has not hosted before but repeat hosts are more than welcome right now! Bjørn is threatening to name YOU as host even if you don't volunteer! Contact him at the Carnival of Evolution blog. You can send articles directly to him or you can submit your articles at Carnival of Evolution although you now have to register to post a submission. Please alert Bjørn or the upcoming host if you see an article that should be included in next month's. You don't have to be the author to nominate a post.
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There was a time when sequencing a gene was just about all you needed to get a publication. Getting a high quality sequence of a typical protein-encoding gene (cDNA) took several years of work—almost sufficient for a Ph.D. thesis.
By the 1990's, that was routine and you needed much more to get a paper published. The genome era had begun and a good paper in a high impact journal required the complete sequence of an entire genome.
Today, you can't get a genome sequence published because it's so easy that undergraduates can do it.
David Smith of Western University (London, Ontario, Canada) laments the death of the genome paper while recognizing that sequencing has probably been abused (Smith, 2013). He makes some good points ...
One of the drawbacks of genome papers, however, is that they can create a mindset of sequence first, ask questions later. I once attended a Masters thesis defense where the external examiner asked the candidate why he sequenced the chloroplast genome of this particular species and what hypothesis was he trying to test. The student, looking startled, answered, "Because the genome hadn't been sequenced before and we didn't know what it looked like." After the defense, I overheard the examiner in the hallway venting to another professor. "We've created a culture of serial genomicists," she exclaimed. "Everyone's jumping from one genome sequence to the next, looking to score a major publication."
Regardless of this opinion, genome papers have provided much of the raw data that have shaped our view of genetics and evolution over the past 20 years. And they can also be a joy to read. Many of my favorite journal articles are genome papers. I remember, when I was a grad student in phycology, eagerly awaiting publication of the genome for Chlamydomonas—the superstar of green algae—and reading it incessantly once it was released, gleaning new insights each time through. There is something intimate and personal in learning about a species' genome. And similarly, if you are part of the team describing the genome, there is a feeling that you're giving the readers a first glimpse at an uncharted territory, with its unique landscape of genes, introns and intergenic regions.
But all of this may be coming to an end. Next generation DNA sequencing techniques have made it easy, fast and cheap to sequence genomes. Today, just about any scientist can walk out their laboratory doors, point to a living thing and say, “I will sequence you!” High-throughput technologies have flooded the academic market with genome papers. And the top journals have responded by only accepting papers describing the most novel, earth-shattering genomes. The less spectacular genomes, much like B-movies, go directly to video, or rather directly to GenBank. This sequencing-vs-publishing arms race has been going on for a long time.
...
Is it time to write the genome paper obituary? Maybe not quite yet. Every now and then they still claw their way into top journals. But the end is not far off, and when it does come, I'm sure that I speak for all of us genome geeks when I say, "Farewell, GP. It was fun while it lasted."
I still like to read genome papers but lately I've been put off by the lack of reliable information in most of those papers. One of things I'm interested in is the number genes, especially the number of unique genes. Unfortunately, the annotation usually relies on computer-generated gene predictions and those are notoriously unreliable.
Smith, D.R. (2013) Death of the genome paper. Frontiers in Genetics 4:1-2. [doi: 10.3389/fgene.2013.00072]
David Klinghoffer isn't impressed by the fact that the DNA of humans and bonobos is 98.6% identical in the areas that can be aligned. Here's what he says at: This Might Be the World's Most Underwhelming Evidence for Darwinian Evolution ...
Oh please. If there are any "creationists" out there who are running scared, they need not do so. The new article [by Chris Mooney] is titled "You Share 98.7 Percent of Your DNA with This Sex-Obsessed Ape," referring, of course, to the precious bonobo, a chimp-like ape famous for its progressive sexual habits. Just by itself, the genetic similarity between us and apes such as the bonobo is supposed to be of knockdown importance.
But what else would anyone expect, whether on a model of Darwinism, intelligent design, or creationism? Apes and humans are similar in many ways, and you don't need Darwinian evolution to see this.
This is a common argument from the IDiots. They assume that the intelligent designer created a model primate and then tweaked it a little bit to give chimps, humans, orangutans, etc. That's why the genomes of these species are so similar.
Unfortunately for them, there's a bit more to it than that. Their model of intelligent design also has to account for the fact that humans are more similar to chimps/bonobos than to gorillas and all three are about the same genetic distance from orangutans. This sequence data correlates with the fossil record over a period of about 10-15 million years.
It gets even worse for the IDiots. Evolutionary theory predicts that the rate of change should correspond to the mutation rate since most of the differences are due to neutral substitutions in junk DNA. We know that the mutation rate is about 130 mutations per generation based on our knowledge of biochemistry. This rate has been confirmed by direct sequencing of parents and children [Estimating the Human Mutation Rate: Biochemical Method] [Estimating the Human Mutation Rate: Direct Method].
If evolutionary theory (population genetics) is correct, and if David Klinhoffer and chimps/bonobos actually evolved from a common ancestor, then we should observe a correspondence between the percent similarity of Klinghoffer and chimps and the predicted number of changes due to evolution.
Let's see if it works.
The human and chimp genomes are 98.6% identical or 1.4% different. That difference amounts to 44.8 million base pairs distributed throughout the entire genome. If this difference is due to evolution then it means that 22.4 million mutations have become fixed in each lineage (humans and chimp) since they diverged about five million years ago.
The average generation time of chimps and humans is 27.5 years. Thus, there have been 185,200 generations since they last shared a common ancestor if the time of divergence is accurate. (It's based on the fossil record.) This corresponds to a substitution rate (fixation) of 121 mutations per generation and that's very close to the mutation rate as predicted by evolutionary theory.
Now, I suppose that this could be just an amazing coincidence. Maybe it's a fluke that the intelligent designer introduced just the right number of changes to make it look like evolution was responsible. Or maybe the IDiots have a good explanation that they haven't revealed?
Or maybe they're just IDiots who don't know what they are talking about.
Creationists are fond of mentioning people who are committed to creationism but still function as successful scientists. We saw an example in the debate between Bill Nye and Ken Ham. These creationist "scientists" are often physicians or engineers.
It seems obvious to most of us that engineers and physicians are not scientists. PZ Myers mentions this on his blog when he discusses the debate as reviewed by William Saletan: Saletan is at it again. Here's what PZ says ...
Engineers can practice real science, but an engineer is not the same thing as a scientist. I agree that creationists can be perfectly good engineers, but how can you trust the scientific acumen of someone who insists that the earth is only 6,000 years old? That says right there that they have no respect for the evidence. How can Saletan ignore Ham’s bogus distinction between historical and observational science, in which he flatly rejects any possibility of inference about the past from the present? This creationism is utterly incompatible with biology, anthropology, geology, astronomy, climate science, geochemistry, cosmology, and any other science that deals with cause and effect and history. These sciences apparently do not matter to Saletan, as long as engineers make satellites and doctors do surgery.
Saletan cites Ham’s videos as falsifying the claim that creationism is incompatible with science. Ken Ham makes a big deal of this, too.
This would be unremarkable except that Jason Rosenhouse disagrees [Saletan vs. Myers on Nye vs. Ham]. Here's what Jason says ...
Oh for heaven’s sake! Engineers are scientists. Full stop. Are you really that desperate to deny that a creationist could ever make a contribution to science that you will sink to this level of insult and idiocy? (Yes, it is insulting to suggest that engineers are not scientists.)
Engineers have a Bachelor's degree in engineering and they typically work for a construction company or in the IT department of a large corporation. They are not scientists. Full stop.
It's true that some engineers do science but usually they have a higher degree in engineering and usually they are academics. There's no possible way you could assume that all engineers are scientists just because they are licensed engineers and wear the ring. I'm sorry, Jason, but you are wrong.
Similarly, the typical physician has a private practice at a strip mall in the suburbs. They have an M.D. degree that can be earned right out of high school (in Europe). They are not scientists.
There are some physicians who are scientists and some of them have earned Nobel Prizes. They are the exceptions, not the rule. It's ridiculous to assume that everyone with an M.D. is a scientist.
Here's a five year old video where Richard Dawkins points to molecular phylogenies as powerful evidence of evolution. He wonders how any creationist could deny the evidence of evolution and suggest that "a mind like that is a disgrace to the human species."
He must have been thinking about Cornelius Hunter because Hunter has resurrected the video in order to show why Dawkins is wrong [Richard Dawkins: How Could Anyone "Possibly Doubt the Fact of Evolution"]. Watch the video and then read what Cornelius Hunter says. You'll recognize some elements of truth in his criticism but you'll also recognize a common creationist fallacy; namely, an inability to see the forest because you've been staring too long at the bark on trees.
What is amazing is the evolutionist’s high confidence and self-assuredness in such a blatant misrepresentation of science. It would be difficult to imagine a bigger falsehood. Phylogenetic incongruence is rampant in evolutionary studies. Conflicts exist at all levels of the evolutionary tree and throughout both morphological and molecular traits. This paper reports on incongruent gene trees in bats. That is one example of many. These incongruences are caused by just about every kind of contradiction possible. Molecular sequences in one or a few species may be out of place amongst similar species. Or sequences in distant species may be strangely similar. As one paper admitted, there is “no known mechanism or function that would account for this level of conservation at the observed evolutionary distances.” Or as another evolutionist admitted, the many examples of nearly identical molecular sequences of totally unrelated animals are “astonishing.”
An even more severe problem is that in many cases no comparison is even possible. The molecular sequence is found in one species but not its neighbors. When this problem first became apparent evolutionists thought it would be resolved as the genomes of more species were decoded. No such luck—the problem just became worse. Not surprisingly evolutionists carefully prefilter their data. As one paper explained, “data are routinely filtered in order to satisfy stringent criteria so as to eliminate the possibility of incongruence.”
Short genes that produce what are known as microRNA also contradict Dawkins’ high claim. In fact one evolutionist, who has studied thousands of microRNA genes, explained that he has not found “a single example that would support the traditional tree.” It is, another evolutionist admitted, “a very serious incongruence.”
Another paper admits that “the more molecular data is analysed, the more difficult it is to interpret straightforwardly the evolutionary histories of those molecules.”
And yet in public presentations of their theory, evolutionists present a very different story. As Dawkins explained, gene comparisons “fall in a perfect hierarchy, a perfect family tree.” This statement is so false it isn’t even wrong—it is absurd. And then Dawkins chastises anyone who “could possibly doubt the fact of evolution.” Unfortunately this sentiment is typical. Evolutionists have no credibility.
Gary Gutting interviews atheist Louise Antony in the New York Times [Arguments Against God]. Here's part of the interview ...
L.A.: Knowledge in the real world does not entail either certainty or infallibility. When I claim to know that there is no God, I mean that the question is settled to my satisfaction. I don’t have any doubts. I don’t say that I’m agnostic, because I disagree with those who say it’s not possible to know whether or not God exists. I think it’s possible to know. And I think the balance of evidence and argument has a definite tilt.
G.G.: What sort of evidence do you have in mind?
L.A.: I find the "argument from evil" overwhelming — that is, I think the probability that the world we experience was designed by an omnipotent and benevolent being is a zillion times lower than that it is the product of mindless natural laws acting on mindless matter. (There are minds in the universe, but they’re all finite and material.)
The argument from evil goes like this ...
- Assume that supernatural, omnipotent beings exist.
- Assume that they are kind and benevolent and they have the power and desire to create human societies that will be kind and good.
- Therefore, because evil is commonplace, one of the assumptions must be wrong.
An atheist is concerned about whether supernatural beings exist so why in the world would they pay any attention to the premises of this argument? If I were to accept the premise that supernatural omnipotent beings exist then the argument from evil simply leads to the conclusion that the supernatural beings are evil (like Satan) or they don't much care about us, like the Greek gods.
The argument from evil says nothing about whether gods exist or not. It only refers to particular kinds of gods and the only way an atheist should pay any attention to it at all is if they are willing to concede that some sort of gods must exist. Then, and only then, can they enter into a discussion about what kinds of gods exist. In that sense, the argument from evil is about as useful as the Courtier's Reply.
I wish atheists would stop discussing the argument from evil because all it does is show that some gods are possible while others are unlikely. I do not see why Louise Anthony finds the argument convincing because it's perfectly consistent with the existence of Satan.
It's also perfectly consistent the god of the Old Testament (see above). That god is exactly the sort of god that that would create a human society full of evil. Humans are behaving just like the god they worship. What's the problem?
A meeting on macroevolution was held at the Field Museum of Natural History in Chicago in October 1980. Normally these meetings would not attract much attention from the press but in this case there was an article published in Discover a month before the meeting took place that suggested something revolutionary was in the wind. Stephen Jay Gould discusses the episode in The Structure of Evolutionary Theory (pp. 981-986).
The article in Discover referred to "growing dissent from the prevailing view of Darwinism" and mentioned that there would be a meeting in Chicago. As a result of this article, a bunch of journalists turned up at the Chicago Macroevolution meeting expecting fireworks.
There was a lot of talk about punctuated equilibria at the Chicago meeting and how the ideas of Eldredge and Gould conflicted with the gradualism that was part of traditional Darwinian evolution. This is complicated stuff so it's no wonder that many journalists misinterpreted the discussion as support for the idea that evolution was being challenged as the creationists claimed.
My students wrote the midterm test today. Here are the questions. They had to answer the first question and 4 other questions (out of 5). How would you do?
- What’s the most important new thing about molecular evolution that you have learned in this course so far? Explain your answer by describing your "important new thing."
- If mutation rates are relatively constant then why does the molecular clock tick at different rates in different proteins?
- Many evolutionary biologists think that population genetics is the key concept in understanding evolution but biology students often complete several years of courses without ever learning about effective population sizes, mutation rates and the importance of random genetic drift. Why? Is it because population genetics is not a necessary key concept in evolution?
- Grad students at this university publish a journal called Hypothesis. A few years ago (2005) there was a student who wrote ...
I am a grad student, and long hours at the bench have got me thinking of other things lately, including the idea of marriage. I came up with a few criteria to direct me on my quest for a wife, and near the top of the list was that she needs to know what a gene is. I thought that this would be a reasonable thing to ask for. I like learning about how we and the rest of life work, and knowing how, in a general sense, cells are programmed to do what they do is a pretty good indicator of similar interest. My friends, however, disagreed with me, and on several occasions, as I shared my list, I feared that things were going to get violent. They argued that I will never get married with such a short-sighted and elitist attitude.
Imagine that you would only seek partners who knew what a gene was. What definition would you require and why?
- What’s the best evidence that a substantial amount of our genome is junk?
- Imagine that you are teaching a class and you ask students to calculate a mutation rate in humans based on what they know about biochemistry. What mistakes are they most likely to make and why?
