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Cambrian Explosion Explained, or Explained Away?

first_imgJames Valentine, an authority on early fossils, has just published a new 600-page book on the Cambrian explosion with the Darwinesque title, On the Origin of Phyla (U. of Chicago Press, 2004).  Stefan Bengtson (Swedish Museum of Natural History) reviewed it in the July 29 issue of Nature.1  He points out that “Darwin wisely called his best-known work On The Origin of Species; the origin of phyla is an even stickier problem, and Valentine deserves credit for tackling it at such breadth.”.  He is not sure, however, that Valentine succeeded in explaining “one of the most significant revolutions in the history of life, the Cambrian explosion.”    One complaint is that in all those pages Valentine said little about the ecology or physical environment in which the “explosion of body plans” took place.  Also, Bengtson is not convinced that the usual explanation is meaningful that a phylum is simply a clade (category) of all animals that diverged from a common ancestor when two body plans diverged in the remote past; “This avoids the question of how body plans arise and whether there may be others not represented by living forms,” he chides.  Worse, Valentine fell into a logical trap, he feels:Defining a body plan isn’t easy, however.  Valentine’s definition, for example, is dangerously circular: “an assemblage of morphological features shared among members of a phylum-level group”.  What does that mean, except that when we define a phylum we also define its body plan, or vice versa?  Valentine proposes to define the origin of a phylum by the acquisition of a key apomorphy – a unique derived trait.  This may be more subjective and less convenient than letting the total (stem and crown) group or the crown group define the phylum, but it gives due priority to biological significance over methodological convenience.  After all, we want to know how different kinds of organism evolve by natural selection, and how they interact with each other and with the environment.  They do that with their phenotypes, not their pedigrees.Bengtson also considers the suggestion that body plans represented “more or less the total number of possible solutions to the problem of being an animal, or whether there were numerous other possibilities that came into being but became extinct because of bad luck or bad design.”  (The evidence shows a decrease in body plans after the explosion due to extinction, not a gradual rise in diversity.)  But is this just explaining away the evidence?The pattern of diminishing evolutionary novelty subsequent to this event, he says, may have been due less to developmental constraints than to a saturation effect (candidates for new adaptive radiations were already available among existing body plans).  He also believes that the Cambrian explosion produced a lot more homoplasies (similar characters with independent origins) than most phylogenetic analyses suggest – in my view an extremely important point that calls for much more careful character evaluation than is commonly done.  He is clearly not impressed, then, by some recent attempts to use fossils to bridge gaps between phyla.If the reader is left wondering how the body plans arose in the first place, the final paragraph of this book review may not be all that satisfying.  How could environmental changes generate the information necessary to produce fins, eyes, jointed limbs, propulsion mechanisms, and so much more that is evidenced in the Cambrian fossils?Valentine seems most happy with intrinsic biological mechanisms for the rapid appearance of phyla.  Large parts of the book deal with developmental prerequisites (such as cell-type numbers and gene regulation) for the event.  Ecological interactions, such as predation, are given more cursory treatment.  As for the physical environment, he merely concludes, somewhat apologetically, that although physical environmental factors were “supremely important”, he does not see any evidence that extraordinary environmental events were causally connected with the Cambrian explosion.  Given that extraordinary environmental events did indeed occur shortly before the explosion, I would give the jury just a little more time to ponder the question.  But first I would make sure they had read this magnificent book.So how did the body plans arise in a geological blink of an eye?  This question was apparently not on the agenda.    Next day in Science,2 R. Andrew Cameron also reviewed Valentine’s book.  This review praised and criticized different things.  Cameron first dismisses the analogy “explosion,” primarily because he claims that molecular studies put the origin of the phyla farther back into the precambrian; consequently, he claims, it was “neither an explosion nor did it happen in the Cambrian,” although he does agree that the Chengjian fossils display “representatives of almost all major groups of animals” (see 07/20/2004 headline).  He mentions the possibility that ancestors were soft-bodied and small, resulting in a poor fossil record; “Perhaps the conditions of the Cambrian environment allowed the rapid appearance of hard skeletal parts, greatly favored fossilization, or both.”  But then he mentions the discovery of “fossil pre-Cambrian embryos from the Doushantuo Formation of southwest China, estimated to be 40 to 55 million years older than the base of the Cambrian,” so being soft and small did not hinder these specimens from becoming fossilized.    Cameron understands the problem of the Cambrian explosion, and claims it is more of a problem now than in Darwin’s day:The question of when and how higher taxonomic groups like phyla evolved differs markedly from the one Darwin addressed 145 years ago in The Origin of Species.  It is not simply different in scale but also in quality.  Although it is somewhat easier to see how changes in single genes can lead to differences among species that render some more capable of surviving in particular environments, it is more difficult to account for the many changes that lead to entirely different bodyplans as a simple accumulation of single-gene effects.  For example, marine stickleback fishes possess bony plates and spines that presumably prevent predation, while their freshwater relatives show a loss of this armor through changes that can be attributed to a single gene [see 06/18/2004 headline].  However, entire organ systems or embryonic germ layers, features that distinguish higher taxa, can be explained in terms of the gene regulatory networks whose architecture is hardwired into the genome.So the question for the origin of phyla is how did these hardwired gene regulatory networks arise?  Cameron claims that Valentine “does not incorporate a molecular model in his final synthesis,” so he offers one himself: major changes might arise through changes in regulatory genes like transcription factors.  Can he give us an example?  “For instance, a morphogenetic program may evolve with relatively minimal changes to establish a new spatial domain of expression for a cell-differentiation program, and the resultant animal has a new body part.”  He does not elaborate.    Cameron praises the first two sections of the book that discuss the origins of the phyla, descriptions of the phyla, and the fossil record.  The third section grapples with the evolution of the phyla.  This section is lacking, the reviewer thinks: “The pictures he delineates here reveal correlations uniting different levels of biological organization, but absent are firm statements about causal mechanisms from which predictions could be made.”    Cameron leaves us with one more concern.  “In view of the volatility of the ideas and the controversy that still exist in this particular area of evolutionary biology, one might argue that it is too early to explain the causes of the origin of phyla.  But as Valentine aptly points out, the time will never be exactly right: there are always more information to incorporate and more ideas to organize.”    Incidentally, Nature also reported discovery of an arthropod fossil that pushes its group, the Euthycarcinoids, back 50 million years into the Cambrian.  “Despite its antiquity and marine occurrence,” they admit with surprise, “the Cambrian species demonstrates that morphological details were conserved in the transition to fresh water.”1Stefan Bengtson, “The body-plan explosion,” Nature 430, 506 (29 July 2004); doi:10.1038/430506a.2R. Andrew Cameron, “Evolution: Hunting for Origins,” Science, Vol 305, Issue 5684, 613-614, 30 July 2004, [DOI: 10.1126/science.1100684].3Vaccari et al., “Cambrian origins and affinities of an enigmatic fossil group of arthropods,” Nature 430, 554 – 557 (29 July 2004); doi:10.1038/nature02705.Satisfied?  Apparently in 600 pages, Valentine did not answer the most basic and fundamental question, how did all this biological complexity emerge in a short time?  Pounding the earth with meteors and tidal waves and volcanoes won’t do it.  Invoking a new predator won’t create an elaborate escape mechanism in the prey; it might just mean the predator will eat everything and then starve.  Cameron’s folklore is simplistic: a regulatory gene mutates and presto!  A new body part!  Can duplicating some protuberance generate an eye?  Come on.    Let’s parse Cameron’s carefully-worded closing lines.  He said, “In view of the volatility of the ideas and the controversy that still exist in this particular area of evolutionary biology, one might argue that it is too early to explain the causes of the origin of phyla.”  Cameron, like Valentine is well aware of the pounding the Darwin Party is getting from the Intelligent Design Movement with the Cambrian Explosion hammer (see The Cambrian Explosion: Biology’s Big Bang by Meyer, Ross, Nelson and Chien (12/01/2003) available online at the Discovery Institute).  The Cambrian Explosion is only controversial because the Darwinians have no answer, and the creationists and ID proponents know it.  So he’s worried that Valentine’s new book is going to provide even more ammo to the enemy.  His coded message to the Darwin Party can be translated, “What do you think you are doing, Jim, letting the creationists know we’re up a creek?  Better to say nothing than to advertise our weaknesses!”    Does anyone see in either of these reviews any real, logical explanation for the explosive appearance of trilobites, worms, jellyfish, corals, and vertebrates, with any evidence to back it up?  Each of these organisms is composed of irreducibly complex cells, and organs made up of irreducibly complex parts.  When they first appear in the fossil record, they are already fully formed and operating.  If the world’s expert can’t explain this after 30 years of thinking about it, then maybe there isn’t an explanation – from a Darwinian viewpoint.  This requires some fresh blood from thinkers not wedded to a dying, outmoded, falsified model that is on the verge of extinction.  Any takers?(Visited 12 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img read more

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MK: In pursuit of liberty

first_imgA display on Solomon Mahlangu, who was hanged in 1979 at the age of 23. This headline refers to the 1980 Silverton Siege, when 25 people were taken hostage in Volkskas Bank, Silverton, Pretoria, by three ANC members who were later allshot dead.(Images: Lucille Davie) MEDIA CONTACTS • Sello Hatang  NMF communications manager  +27 11 547 5600• To arrange an appointment to view:  Ethel Arends  MNF records management specialist  +27 11 547 5676. RELATED ARTICLES • Tribute to Arthur Goldreich • Liliesleaf to sprout new hotel • Sharpeville remembered • SA, Angola strengthen ties • New ward opened for Smile WeekLucille DavieAfrican National Congress (ANC) military wing Umkhonto we Sizwe (MK) turns 50 this year, and in commemoration, the Nelson Mandela Foundation is hosting an exhibition highlighting the organisation during its active period.Movingly displayed in the foyer of the foundation’s offices in Houghton, the exhibition is titled In pursuit of liberty: legality vs justice. Its theme is “heroism, martyrdom and the ethical principles of South African liberation movements”.Visitors can learn about the struggle of MK cadres against apartheid.The exhibition has three main areas of focus – the Rivonia triallists and their capture at Liliesleaf; the story of Solomon Mahlangu who in 1979 became the first MK soldier to be executed by the government of the time; and the 1980 bank siege in Silverton, Pretoria, and the subsequent Soekmekaar and Silverton trials, which became the “turning point of the liberation struggle”.“The exhibition portrays how freedom fighters used the apartheid courts and police holding cells as sites of struggle,” said a press statement.“It evokes unpleasant memories of the turbulent apartheid years, but it can help those who were born after the dawn of democracy to understand the heavy price their forebears paid for democracy.”In pursuit of liberty runs until the end of 2011. Viewing is by appointment only.The South African Post Office, which is a participant in the exhibition, will issue a new set of stamps in support of its successful Legends of Freedom series and its 2009 Solomon Mahlangu stamp.The struggle for freedomIn a moving address at the exhibition’s opening, during which she sang a verse of a freedom song, Deputy Minister of Public Service and Administration Ayanda Dlodlo talked about her time in MK.“Ours was a just war and it should be celebrated,” she said. “It was a war that had to be fought to find freedom.”She described the “vigorous training” that she and many other young South Africans went through in the 1970s, after they left South Africa in the wake of the 16 June 1976 Soweto pupils’ uprising.Dlodlo thanked guest and respected advocate George Bizos, who defended Nelson Mandela, Walter Sisulu and Govan Mbeki in the Rivonia Trial, for his support during the struggle years.She also mentioned the citizens of various countries, including Angola, Mozambique, Russia, Sweden and Cuba, who welcomed exiled MK members within their borders. People like the late Zimbabwean politician Joshua Nkomo, music producer Quincy Jones, former Cuban president Fidel Castro, and the Reverend Jesse Jackson had also offered unfailing support to the ANC.“Whites were not our enemy, the system was the enemy,” she said.Dlodlo, who is also secretary-general of the Military Veterans Association, stressed that many comrades in exile were young – some were 18 and 19 years old. The women cadres in exile were called “flowers of our revolution”, a term originally coined by ANC leader in exile Oliver Tambo.Continuing the fightJames Mange, an MK commander who was arrested with Mahlangu and 12 others, described his experience of the trial, and how the death sentence hung over them.“There was no doubt in our minds that John Vorster would hang Solomon,” he said, referring to the state president at the time.Despite a two-year wait during which the government came under intense international pressure to repeal his sentence, Mahlangu went to the gallows in 1979. His hanging “just gave us strength and more determination,” added Mange.Mahlangu’s long incarceration had not broken his spirit, and his last words were reportedly: ”My blood will nourish the tree that will bear the fruits of freedom. Tell my people that I love them. They must continue the fight.”Like a number of struggle heroes, he posthumously received the National Order of Mendi for Bravery, in 2005.Mange, too, was sentenced to death while his comrades were sent to Robben Island, but this fate was commuted to a jail term of 20 years after an appeal.“We were afraid to disgrace the generation before us,” he said, and added that the present generation needs to learn about the sacrifices made by his generation, as they go forward into the future.Taking up armsUmkhonto we Sizwe is isiZulu and isiXhosa for “Spear of the Nation”. The movement played a major role in South Africa’s armed struggle.The decision to form MK was taken in mid-1961 in response to the government’s increasing and sometimes lethal determination to oppress non-white South Africans, despite the fact that resistance action had been peaceful until then. The ANC decided that it had no choice but to take up arms.MK’s founding members were, among others, former president Nelson Mandela and Joe Slovo, the secretary-general of the South African Communist Party.Other key members in cells around the country included Jack Hogson, Ahmed Kathrada, Arthur Goldreich, Chris Hani, Dennis Goldberg, Ronnie Kasrils, former president Thabo Mbeki, current president Jacob Zuma, Curnick Dlovu and Vuyisile Mini.MK announced its presence with a series of bomb attacks on government buildings on 16 December 1961 in Johannesburg, Durban and Port Elizabeth. Now the Day of Reconciliation, the 16 December public holiday formerly commemorated the Afrikaner defeat of the Zulus at the Battle of Blood River in 1838, and was known as the Day of the Covenant or Dingaan’s Day.The government promptly banned MK as a terrorist organisation, but this didn’t stop many cadres from receiving military training overseas. During its years of activity the organisation’s operations included sabotage of transport systems and power plants – including the Koeberg nuclear facility – attacks on police stations and military bases, and bomb blasts of varying intensity.Despite fierce resistance from the government and two states of emergency, the first one in 1960 and the second in 1986, the apartheid system eventually fell away.After 29 years MK suspended its armed struggle when the ANC and other organisations were unbanned in 1990, four years before South Africa’s first democratic elections. It was completely absorbed into the National Defence Force by 1994.A display on Solomon Mahlangu, who was hanged in 1979last_img read more

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Giving taxis a good name

first_imgEntrants from previous competitionshave become better drivers throughthe countrywide training opportunities.(Image: Arrive Alive) This year four of the country’s bestdrivers will win a snazzy Ses’ifikile taxi.(Image: Imperial Toyota)Janine ErasmusThousands of South African minibus taxi drivers who take pride in their work are competing for the coveted title of the country’s best.The Number One Taxi Driver competition has been running since 2004, with the 2011/2012 edition launched in December and the national finals scheduled to take place in June.The initiative was started by beverage company brandhouse, and is the flagship of its corporate social responsibility efforts to promote the responsible use of alcohol.With top brands such as Smirnoff, Amstel, Heineken and Captain Morgan in its portfolio, the company identified the taxi sector – with its vast reach into and influence on South African society – as the ideal target for the Number One competition.Working with Toyota South Africa, Caltex, the Department of Transport and the Road Traffic Management Corporation, brandhouse seeks to place responsible role models in the taxi industry, ready and able to inspire and educate their colleagues in road safety and good customer care.“The campaign is one of our key community enrichment programmes at brandhouse, aimed at not only promoting road safety within the minibus taxi industry but providing valuable skills to the drivers,” said brandhouse MD Gerald Mahinda.It’s a crucial part of the company’s efforts to make a meaningful difference in the lives of the communities that support it, he said. Over 25-million people use minibus taxis every day, and the general public opinion is that drivers are reckless and have very little regard for their passengers or fellow drivers.“Their bosses want money so they’re working under very strict conditions and it pushes them to go over emergency lanes and to drive recklessly,” said driving instructor Sthembiso Segolela, speaking at a testing session.Thousands of drivers to improve their skillsThe competition is promoted annually by distributing entry forms at taxi ranks, shopping centres and tollgates, and also through roadshows and other events, and has attracted thousands of hopefuls over the years.In this year’s competition, over 3 500 taxi drivers across the country have received training, in 53 testing sessions.The best of the best stand to win a 14-seater Ses’ifikile taxi, courtesy of Toyota – there will be four big winners this year – and each of the top provincial finalists will get petrol to the value of R50 000 (US$6 300)  from Caltex. To top all of that, six taxi owners will each win fuel worth R20 000 ($R2 500) and three will get a R15 000 ($1 900) fuel package.Participating drivers are tested on their theoretical and practical knowledge and are trained in advanced and defensive driving procedures, such as keeping a correct following distance, the safest way to stop, and driving in bad weather. The Toyota Advanced Driving Academy conducted the testing in all nine provinces and will also oversee the final round.Adjudicators are currently adding up the scores to identify the finalists from each province.Of the 27 shortlisted drivers, only nine will make it to the last round, but the remaining 18 will each receive R3 500 ($444) just for taking part, and will also take away invaluable skills learned along the way.The finals will take place at the Gerotek facility in Hartebeespoort, northwest of Johannesburg. A division of Armscor Defence Institutes, Gerotek is a multi-purpose organisation that encompasses consultation, training, testing and evaluation services to the industrial, military and commercial vehicle industries.The chance of a lifetimePrevious winners and now proud owners of their own vehicles have used the opportunity to put their entrepreneurial ideas into practice.Mpumalanga’s Raymond Ngomane, the 2010 winner, wanted to be a better driver, but also had his eye on the top prize. He said his life has changed dramatically since being named the country’s best taxi driver.“Through this initiative, I have managed to realise both of my wishes. I am now a proud and responsible taxi owner,” said Ngomane, who is the sole breadwinner for his family. His first passenger was his 89-year-old grandmother.The winner in 2008 was Godfrey Mosala from the North West province, and in 2009 it was Lunga Ronnie Tilolo from the Eastern Cape who drove off with the big prize.last_img read more

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App.net Hackathon: This Is The Energy Twitter Lost

first_imgTwitter, with its vague, airy blog posts masking stern new rules, is chasing away third-party developers. Here’s what a social tech company that loves its developers looks like: The first ever App.net Hackathon was held the weekend of October 20, and a bunch of independent programmers used the event to transform the service overnight.“I was really excited to meet all of these folks in person,” said App.net founder Dalton Caldwell. “I knew probably 80% of the people there by their username. Getting the chance to meet people that you have interacted with online is always fun.” Tags:#App.net Related Posts 8 Best WordPress Hosting Solutions on the Market A Great Start“Most hackathons I’ve attended in SF have a noticeable percentage of attendees that are there exclusively to headhunt technical cofounders or network for investor connections,” says Abraham Williams, who built the website follow button and worked on other such widgets. “Everyone at the ADN hackathon was there because they were personally passionate about the platform or the space. While number of people with alternative motives will increase with the popularity of ADN, last weekends experience was at least temporarily refreshing.”“The vibe was friendly and collaborative,” App.net’s Ben Friedland said. “It was less a hackathon (in terms of competition) and more a weekend working group, powered by soda and BBQ.”“The vibe was especially cool because of how many people are not local to SF,” added Caldwell. “I would guess at least 20% of the people there live in a foreign country, not to mention the folks that don’t live in the Bay Area but came to town specifically for it.”In keeping with the experimental spirit he and I discussed on video in September, Caldwell “was interested to see the scope and ideas of projects expand to different sorts of use cases. For instance, the group video watching app [Vidcast] and the lightweight blogging service.”To see more photos and hackathon projects, check out the App.net blog post.Here’s the video of all the presentations (warning: it’s an hour long):Video streaming by UstreamPhotos courtesy of App.net jon mitchell A Web Developer’s New Best Friend is the AI Wai… Apparchy In The U.S.A.One developer, Steve Streza, whose day job is building Pocket, build something downright subversive that I love. It’s called apparchy. It lets you break open the official Twitter clients for iPhone and iPad and use them for App.net instead.“The reason I made this is because, well, I could,” Streza explained. Twitter’s service can be swapped out for other domains in order to allow proxy access in places where Twitter is blocked, such as repressive countries. “But by putting a server in there which caught requests, made calls to the app.net API, and rewriting them as if they were from the Twitter API, [apparchy] fools the app into thinking that it’s getting tweets from Twitter.”I think this hack is delightful. Twitter used to be a developer’s playground, and third-party inventions made the service a global phenomenon. Now it’s cracking down. Enterprising developers like these, who used to build on Twitter, have turned to App.net, which is built to motivate developers to build great apps. Streza’s apparchy embodies that hacker spirit just for the pure joy of it.App.net co-founders Bryan Berg and Dalton Caldwell Top Reasons to Go With Managed WordPress Hosting Why Tech Companies Need Simpler Terms of Servic… Some of the hackathon projects helped flesh out the core features of App.net:Abraham Williams created an App.net follow button for websites that uses only a single line of code.Ketan Majmudar and Andrew Schmidt worked on an app called Pigeonhole, which tags and stars App.net posts so you can organize and find them later.Chad Etzel, who also develops the iOS App.net client Adian, built a service called ADN Blogs, which turns App.net posts into full-length blog posts, sharing a link and headline on App.net.Tony Million added an Explore feature to his excellent iPhone App.net client, Rivr, which uses the geolocation built into App.net, so users can see where posts come from on a map.last_img read more

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RED Cameras hit Apple and B&H Stores, and a First Look at HYDROGEN

first_imgThose who purchase the RED RAVEN 4.5K kit from Apple will receive a free copy of Final Cut Pro X and an iOS app. The foolcontrol app is exclusively for RED RAVEN Camera Kit owners. The app allows full control over the RAVEN when connected to the same network as your iOS device.You will soon be able to demo the RED RAVEN kit in select Apple Stores. It must be getting a little crowded these days, as DJI will also be selling select drones in Apple Stores as well. It should also be no surprise that the only suggested products for RED on the Apple site are a pair of Beats by Dre headphones and AirPods.This makes me wonder if the partnership may also have something to do with RED’s HYDROGEN phone. The device will take on the Apple iPhone, though RED already said the HYDROGEN was Android OS-based. Some already speculate that the partnership has to do with requests from RED for Apple to produce a better and more capable MacPro for professional video editors.Speaking of the HYDROGEN, the first look at the device also hit this week. Marques Brownlee got his hands on the new holographic smartphone from RED, and in this video, he walks you through the prototypes and tells us we should see a nearly finished product in the next month or so.For more about the RED cameras, you can check out RED cameras and accessories at B&H and the RED RAVEN kit at Apple. The first look at the RED HYDROGEN and RED DIGITAL CINEMA now offers their cameras and accessories on exclusive reseller sites.Top image via MKBHD and RED.It was only back in July that B&H announced that they would now carry RED cameras in their stores, and now RED has announced an exclusive deal to sell the RED RAVEN in the Apple Store.On B&H, you can find just about any RED accessories you may need. Cameras currently available on B&H include the EPIC-W HELIUM 8K S35 and the SCARLET-W DRAGON 5K.As for the Apple deal, Apple is now the exclusive dealer of the RED RAVEN —  a camera you couldn’t even buy on RED’s own site for the past few months.The RED RAVEN kit at Apple includes all of the following for $14,999.95:RED RAVEN 4.5K camera BRAINRED DSMC2 Touch LCD 4.7″ MonitorRED DSMC2 Outrigger HandleRED V-Lock I/O ExpanderRED 120 GB RED MINI–MAGTwo IDX DUO-C98 batteries with VL-2X chargerG-Technology ev Series RED MINI–MAG ReaderSigma 18-35mm F1.8 DC HSM | ArtNanuk heavy-duty camera caseFinal Cut Pro Xfoolcontrol for RAVEN Camera Kitlast_img read more

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