25 years ago, according to a recent article in Science magazine, Richard Lenski put samples of E. coli bacteria into a dozen flasks filled with a solution of glucose and other nutrients, incubated them, stirred them, and every day removed 1 % and repeated the process, day after day, for 25 years (except for a brief interruption when he moved from one university to another). The author of the article, Elizabeth Pennisi, notes that Lenski’s bacteria
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Not stated is whether they manage to lose weight, nor whether they still get cavities or develop diabetes. But a recent article in Science shows that cockroaches evolved an aversion to glucose after glucose was used for a number of years as a poisoned bait. That is, the cockroaches developed an aversion to the bait rather than a resistance to the poison. The Science article is kind of written in Greek
In response to the anthropogenic assault of toxic baits, populations of the German cockroach have rapidly evolved an adaptive behavioral aversion to glucose (a phagostimulant component of baits).
but The New York Times has a nice summary and notes, almost as a throw-away, that the result might have application to diseases, such as malaria, that are spread by mosquitoes.
Memo to potential trolls: Yes, yes, we know—they are still cockroaches!!
… a new model/mechanism by which duplicated genes can retain the selection pressure to not succumb to deleterious mutations. They call it the innovation-amplification-divergene model (IAD).
IAD works like this: A gene initially has one function only (A). Then some genetic changes makes it also have a new function, b, which at first is not of too great importance. Then some environmental change favors the gene variants with the minor b-function (the innovation stage). This is then followed by duplication of the gene, such that there are now more than one copy that carries out A and b (the amplification stage). At this stage there is selection for more b, and at some point genetic changes in one of the copies results in a gene that is better at the new function, B. At this point, selection for the genes that do both A and b is relaxed, because the new gene (blue) carries out the new function. The original gene then loses the b function, and we are left with two distinct genes.
Michael Behe, of course, scoffs. Because the researchers did some manipulations that created conditions favorable to the evolution of the new function, Behe claims that
Needless to say, this ain’t how unaided nature works – unless nature is guiding events toward a goal.
Shucks. I guess every experimental manipulation ever performed has been an invalid method of studying some process. But as a PT crew member pointed out on the back channel, “this kind of shit happens all the time in nature.” See, for example, Gene duplication and the adaptive evolution of a classic genetic switch or Escape from adaptive conflict after duplication in an anthocyanin pathway gene.
An article in Friday’s Science magazine details how a team of scientists provided a calibration for carbon dating accurately to 50,000 years, or about 10 times the age of the earth according to many creationists.
Until now, carbon dating was accurate only to about 13,000 years, or the ages of the oldest trees. The Science article is fairly dense, but Science has provided a helpful Perspective, and Popular Science has a nice article as well.
It turns out that the concentration of 14C in the atmosphere varies from year to year, so calculations of the age of a specimen need to be corrected for this yearly variation; uncorrected calculations are not wrong, but they may be in error by hundreds of years. Until now, we have had no detailed record of the 14C concentration beyond the age of the oldest trees. Now, however, a team led by Christopher Bronk Ramsey of the University of Oxford has examined sediments in a Japanese lake and extended carbon dating to approximately 50,000 years. The lake was chosen because the bed of the lake is anoxic and its sediments are thought to have been stable and untouched by ice-age glaciers. The new calibration will be significant to archeology and studies of climate change. Read the 2 articles I have cited for more detail.
Not an earthshaking discovery, to be sure, but it shows how science progresses, step-by-step, while creationism merely stagnates.
Acknowledgment. Thanks to Rolf Manne of the University of Bergen, Norway, for alerting me to the importance of Bronk Ramsey’s article.
There has been a good deal of publicity recently about the sequencing of the Denisovan genome by Svante Pääbo’s group at the Max Plank Institute (see here and here for examples). Using brand new technology for sequencing single strands of DNA (single strands as opposed to the normal double-strand), the group was able to achieve a sequencing rate of 30x–every position in the genome was sequenced 30 times. That’s comparable to sequencing modern genomes.
While some of the coverage has focused on what can be inferred about the individual from whom the DNA was recovered (female, dark skin, brown eyes and hair) what is much more interesting are the relationships of the Denisovans to various modern human populations and to Neandertals. Also interesting is the identification of genetic changes that have occurred in modern humans, a number of the changes having to do with genes associated with brain function and nervous system development,
Since John Hawks has discussed the paper in some detail, I won’t, but will direct you to Hawks’ review of the research. One quotation from that piece–the final sentence–is worth repeating:
Evolution really is the fundamental principle of biology, but using evolution to learn about biology sometimes requires traveling through time. Ancient DNA gives us a time machine bringing new insights into reach.
I can hear the echo of Ken Ham’s minions mindlessly shouting “Were you there???” No, but this is the next best thing.
Evolution 2012 is starting tomorrow! This time it’s in Ottawa, representing the First Joint Congress on Evolutionary Biology – a meeting of the American Society of Naturalists (ASN), the Canadian Society for Ecology and Evolution (CSEE), the European Society for Evolutionary Biology (ESEB), the Society for the Study of Evolution (SSE), and the Society of Systematic Biologists (SSB).
Sadly, though, I can’t go this year. A good friend of mine is having her wedding right in the middle of the meeting. There’s only one wedding in someone’s life (well, hopefully!) and there are a lot of meetings, so I picked the wedding. I guess the wedding won’t be entirely evolution-free, seeing as the bride studies extinct giant sloths.
But at the moment I’m looking over the program for Evolution 2012 and experiencing a few missing-the-conference blues.
Ah, but here’s something to cheer me up. After you’ve been in science for awhile, you discover that you don’t even have to be at a meeting for your name to get into the program, due to the collaborations you are involved with! Here are the papers I’m a coauthor on:
Well, I just got interviewed about this, so I suppose I should blog it! Today a review paper is coming out in Nature entitled “Approaching a state shift in Earth’s biosphere” (Nature, UC Berkeley press release) It is getting a huge amount of press, in part because of the message, and in part because of the upcoming United Nations Rio+20 Earth Summit in Rio de Janeiro.
The message of the paper is that, while much is uncertain, we think that the biosphere – the global community of species and ecosystems – is heading for a “state shift”, or “tipping point”, due to human activity. More on what exactly this means in a moment.
So, apparently, do some robots. Well, simulated robots, anyway.
The TalkOrigins Archive has two articles (here and here) on observed instances of speciation. Now a recent PNAS paper describes speciation in Aspidoscelis, a genus of whiptail lizards. The paper is titled “Laboratory synthesis of an independently reproducing vertebrate species.” From the abstract:
Here we report the generation of four self-sustaining clonal lineages of a tetraploid species resulting from fertilization of triploid oocytes from a parthenogenetic Aspidoscelis exsanguis with haploid sperm from Aspidoscelis inornata. Molecular and cytological analysis confirmed the genetic identity of the hybrids and revealed that the females retain the capability of parthenogenetic reproduction characteristic of their triploid mothers. The tetraploid females have established self-perpetuating clonal lineages which are now in the third generation.
Read more at Nobel Intent, to which we tip our hat.
The Reverend Thomas Bayes died 250 years ago this month, in 1761. His famous “Essay Towards Solving a Problem in the Doctrine of Chances”, from which stems “Bayes’ Rule”, was published posthumously 247 years ago in 1764 by the Royal Society. A detailed review of the argument in modern notation is Edwards (1978) in the Scandanavian Journal of Statistics. Any of us scientists working today would be beyond lucky to have our work cited 250 later!
The R Revolutions blog highlights the anniversary and is posting videos explaining the significance of Bayesian thinking. Check it out!
Contrary to what creationists believe, evolutionary biologists don’t sit around in biology departments plotting to overthrow God and morality. We spend our time doing things like statistics and programming and specimen preparation and experimental manipulation and DNA sequencing and field observation, and then give and hear talks and discussions about this research. The main thing we are interested in is not “proving evolution”, it is discovering cool facts and devising hypotheses to explain them, and then devising tests of those hypotheses (typically, statistical tests, something which creationists almost always ignore). In short, it’s like any other science.
This paper is a case in point:
NATURE | REVIEW
Barnosky, Anthony D.; Matzke, Nicholas; Tomiya, Susumu; Wogan, Guinevere O. U.; Swartz, Brian; Quental, Tiago B.; Marshall, Charles; McGuire, Jenny L.; Lindsey, Emily L.; Maguire, Kaitlin C.; Mersey, Ben; Ferrer, Elizabeth A. (2011). “Has the Earth’s sixth mass extinction already arrived?” Nature 471(7336), 51-57. (DOI - Link)
The Sensuous Curmudgeon calls our attention to a new study by researchers at the University of Illnois and the Chinese Academy of Sciences that traces the evolution of a new function via gene duplication. Since I’m not a molecular guy, I’ll very briefly describe it and refer you to the news release and published paper (behind the PNAS paywall). Very briefly, the Antarctic eelpout has a gene that codes for an antifreeze protein, a member of a protein family called AFP III, that enables the eelpout to survive the freezing temperatures in Antarctic waters. It has been hypothesized on genetic homology grounds that the antifreeze gene evolved via duplication of a gene that codes for sialic acid synthase, a cellular enzyme, and subsequent selection for the antifreeze function in one of the duplicates via an escape from adaptive conflict process. From the linked news release:
“This is the first clear demonstration - with strong supporting molecular and functional evidence - of escape from adaptive conflict as the underlying process of gene duplication and the creation of a completely new function in one of the daughter copies,” Cheng said. “This has not been documented before in the field of molecular evolution.”
And from the Abstract:
We report here clear experimental evidence for EAC-driven evolution of type III antifreeze protein gene from an old sialic acid synthase (SAS) gene in an Antarctic zoarcid fish. We found that an SAS gene, having both sialic acid synthase and rudimentary ice-binding activities, became duplicated. In one duplicate, the N-terminal SAS domain was deleted and replaced with a nascent signal peptide, removing pleiotropic structural conflict between SAS and ice-binding functions and allowing rapid optimization of the C-terminal domain to become a secreted protein capable of noncolligative freezing-point depression. This study reveals how minor functionalities in an old gene can be transformed into a distinct survival protein and provides insights into how gene duplicates facing presumed identical selection and mutation pressures at birth could take divergent evolutionary paths.
As the Curmudgeon points out, this is precisely the kind of evidence that Disco ‘Tute attack mouse Casey Luskin asked for a year ago:
Many scientific papers purporting to show the evolution of “new genetic information” do little more than identify molecular similarities and differences between existing genes and then tell evolutionary just-so stories of duplication, rearrangement, and subsequent divergence based upon vague appeals to “positive selection” that purport to explain how the gene arose. But exactly how the gene arose is never explained. In particular, whether chance mutations and unguided natural selection are sufficient to produce the relevant genetic changes is almost never assessed.
There it is, Casey.
In Ediacaran roots extend deeper in time? Joe Meert described enigmatic fossil impressions that could be interpreted as Ediacaran metazoa (multi-celled animals) from strata some 100 million years older than previously known. Now Chris Nedin, a palaeontologist who has worked with Ediacaran and early Cambrian material, has a comprehensive post on his blog Ediacaran titled “770Ma Ediacara (?) Fossils from Kazakhstan (sadly no)”:
Two questions to be asked then. Are these deposits c. 770 million years old? Are these specimens examples of Ediacaran fossils?
I think the answer to the first question is yes, and the answer to the second question is no. I’ll explain below.
Leave comments here or there; Joe has already commented there.
A news article in today’s issue of Science suggests that global warming may drive many lizards to extinction. I have not read the technical article, which you may find here. According to the news article, Barry Sinervo of the University of California, Santa Cruz, and his colleagues suggest that lizards, which generally can tolerate high temperatures, may nevertheless suffer if the periods of high temperature grow longer. Specifically, if the lizards have to spend more time protecting themselves from the heat, then they become less fit because they must spend less time foraging for food. Sinervo and colleagues note that Mexico has lost 12 % of its lizard species in the last 35 years, and they suggest that 40 % of lizard populations could disappear and 20 % of lizard species could become extinct by 2080. Additionally, Sinervo says here that lizards that can move to higher elevations may end up outcompeting other species and driving them to extinction, so the 20 % figure may be conservative.
A common bleat from creationists is “Where are the millions of transitional fossils Darwin said there should be?” Martin Brazeau has an excellent post on taphonomy at The Lancelet reporting a paper in which folks let poor innocent critters rot in order to ascertain which anatomical features are likely to be preserved and which are likely to be lost before fossilization, and the implications for interpreting fossils of ‘soft’ tissues for phylogenetics. Comment there, please.
Hello from Kearney Nebraska, where I am lucky to be a speaker along with a great number of actually famous people at the University of Nebraska’s Evolution2009 conference. I am mostly offline at the moment, but I have been told that the Darwin Correspondence Project in Cambridge has just announced that I have won the prize for one of their competitions – finding the true source of a famous, but bogus, quote of Darwin. The quote goes as follows (there are many varieties):
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.
David Hone, a British paleontologist working in China who blogs at Archosaur Musings, has a fascinating post on tracking the reporting of a paper he recently published. Among other things, he was able to follow the ‘Chinese whispers’ or ‘telephone game’ transmission of the news stories by tracking errors that crept into the story as it was published here and picked up there:
Thus science stories can really pick up and spread this way, so although 24 hours after my press release I had only one mention in one paper, after 48 hours this was more than five and another 24 hours later this was more than twenty. One week later it’s up to about fifty and I am still getting new e-mails about this.
This spreading though is especially interesting as between the original press release(s), the paper itself and the blog post (and later interviews) I know which quotes and which information came from where and thus which errors or changes have come in at which stage and which media have picked them up from which other. It is noticeable therefore that one can track errors from report to report as they originate in one and then are copied to others (I tracked a spelling mistake of Tyrannosaurus as Tyrannosaurs across three generations of articles, and each time it appeared in basically the same sentence in the second paragraph of the report, each, theoretically written by a different journalist).
Shades of pseudogene phylogenies! Go and read it and enjoy it there, and comment there if you feel moved to do so to encourage him to keep ‘em coming.