Ah sorry dan heb ik het verkeerd gelezen. Is die scientific american trouwens een beetje de moeite waard? Ben je lid of heb je er eentje ergens meegepikt?quote:Op dinsdag 1 mei 2007 01:17 schreef Cruoninga het volgende:
Heb hier de papieren (Nederlandstalige) versie van Scientific America voor me. Nummer 3 van 2007.
Kankercellen zijn niet de aanstuurder van de ontwikkeling van het brein, maar hebben er zijdelings van geprofiteerd door mee te snoepen van een eiwit dat nodig was om het brein te ontwikkelen.
http://www.physorg.com/news97825267.htmlquote:Gene mutation linked to cognition is found only in humans
The human and chimpanzee genomes vary by just 1.2 percent, yet there is a considerable difference in the mental and linguistic capabilities between the two species. A new study showed that a certain form of neuropsin, a protein that plays a role in learning and memory, is expressed only in the central nervous systems of humans and that it originated less than 5 million years ago. The study, which also demonstrated the molecular mechanism that creates this novel protein, will be published online in Human Mutation, the official journal of the Human Genome Variation Society.
quote:Research confirms theory that all modern humans descended from the same small group of people
he genetic survey, produced by a collaborative team led by scholars at Cambridge and Anglia Ruskin Universities, shows that Australia's aboriginal population sprang from the same tiny group of colonists, along with their New Guinean neighbours.
The research confirms the “Out Of Africa” hypothesis that all modern humans stem from a single group of Homo sapiens who emigrated from Africa 2,000 generations ago and spread throughout Eurasia over thousands of years. These settlers replaced other early humans (such as Neanderthals), rather than interbreeding with them.
http://www.physorg.com/news97857326.htmlquote:Until now, one of the main reasons for doubting the “Out Of Africa” theory was the existence of inconsistent evidence in Australia. The skeletal and tool remains that have been found there are strikingly different from those elsewhere on the “coastal expressway” – the route through South Asia taken by the early settlers.
Some scholars argue that these discrepancies exist either because the early colonists interbred with the local Homo erectus population, or because there was a subsequent, secondary migration from Africa. Both explanations would undermine the theory of a single, common origin for modern-day humans.
But in the latest research there was no evidence of a genetic inheritance from Homo erectus, indicating that the settlers did not mix and that these people therefore share the same direct ancestry as the other Eurasian peoples.
Weer een nieuwe stap in de discussie tussen enerzijds de wetenschappers die de "single origin and replacement hypothesis" verdedigen, en anderzijds de wetenschappers die.. niet zozeer meer het multiregionale model, maar wel een kleine mate aan hybridisatie met archaische mensensoorten (neanderthal, erectus) willen aantonen.quote:Op donderdag 10 mei 2007 10:16 schreef Monolith het volgende:
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http://www.physorg.com/news97857326.html
Ik denk dat je dan een stukje moet vertalen van talkorigines. Ik ken eigenlijk maar weinig nederlandse sites met een "bewijs" - "tegenbewijs" format over dit onderwerp.quote:Op maandag 14 mei 2007 08:12 schreef bigore het volgende:
We hadden dit weekend familieweekend, en de vader van me vriendin kwam naar me toe met een mooi gekopieerd stuk uit het boek, Moderne wetenschap in de bijbel van Ben Hobrink.
Het ging over Buitenissige dieren, de explosieve kever. Stond heel mooi in dat dat bewijs is dat evolutie nooit heeft kunnen plaatsvinden, ik probeer nu antwoord te vinden op een nederlandse site, maar er is niet bepaald veel over geschreven. Talkorigin heeft er wel een mooi stuk over wat ik uitgeprint heb, maar haar vader kan amper engels, dus ja...
Heeft iemand misschien een Nederlandse site voor zulk soort vraagstukken? Ik word namelijk telkens naar creationisten sites gestuurd in google.
Toch jammer, aangezien er talloze creationisten sites zijn in het Nederlands. Talkorigins, word dat beheerd door wetenschappers of door een stel n00bs?quote:Op maandag 14 mei 2007 10:10 schreef SpecialK het volgende:
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Ik denk dat je dan een stukje moet vertalen van talkorigines. Ik ken eigenlijk maar weinig nederlandse sites met een "bewijs" - "tegenbewijs" format over dit onderwerp.
Ze hebben om wiki maar even te quoten zeker wel een aardige status weten te verwerven:quote:Op maandag 14 mei 2007 15:13 schreef bigore het volgende:
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Toch jammer, aangezien er talloze creationisten sites zijn in het Nederlands. Talkorigins, word dat beheerd door wetenschappers of door een stel n00bs?
http://en.wikipedia.org/wiki/TalkOrigins_Archivequote:Awards
Talkorigins.org has gained many awards and achieved substantial recognition.[4]
In August 2002 Scientific American recognized Talkorigins.org for its "detailed discussions (some of which may be too sophisticated for casual readers) and bibliographies relating to virtually any objection to evolution that creationists might raise."[5]
The webpages of the National Academy of Science, Smithsonian Institute[6], The Leakey Foundation[7], the National Center for Science Education[8] and other organizations recommend Talkorigins.org.
Biomednet gave the Archive four stars.[specify]
The Archive is also referenced in college-level textbooks[9] and has had material from the archive incorporated into over 20 college or university courses.[10]
not so brainy....quote:Human ancestor not so brainy
By Will Dunham
A monkey-like animal seen as an ancestor of monkeys, apes and humans was not as brainy as expected, according to scientists who analyzed its nicely preserved 29-million-year-old skull.
The finding indicated that primate brain enlargement evolved later than once thought, the researchers said on Monday.
They analyzed a remarkably well-preserved fossilized skull of the little primate Aegyptopithecus zeuxis, which lived in the trees and ate fruit and leaves about 29 million years ago in warm forests in what is now an Egyptian desert.
A technique called microcomputerized tomography scanning -- a computerized X-ray method also called micro-CT -- allowed them to determine the dimensions of the animal's brain.
"What was astonishing is how small this brain is," Duke University primatologist Elwyn Simons, who led the study in the Proceedings of the National Academy of Sciences, said in a telephone interview.
"You can also see it's a pretty darn primitive brain. It would be small for a monkey or an ape," Simons added. "So it's telling us that the speed of achievement of brain enlargement in primates was a little slower than perhaps we had thought."
This skull of a small female was uncovered in a quarry southwest of Cairo in 2004. It was better preserved than another skull of a larger male of the species found in the same area in 1966.
Based on earlier finds, scientists had theorized the species had a relatively large brain. Instead, it had a brain that might have been even smaller than that of a modern lemur, a primate with primitive traits.
The condition of the earlier skull -- "smashed up," as Simons put it -- prevented the analysis possible with the newer one.
"YOU NEED TO BE SMARTER"
Simons said that when this primate lived, Africa was an island, limiting the competition for survival. Simons said brain enlargement may have evolved in this lineage after Africa became connected to Asia, bringing in more animals including new and dangerous predators.
"Brain-volume enlargement is favored under conditions of competition because you need to be smarter," Simons said.
Aegyptopithecus is sometimes called "Dawn Ape." Simons said it looked somewhat like an ape, particularly in its teeth and skull, and said it is thought to be close to the ancestry of monkeys, apes and humans.
"Because of the proportions of having a fairly robust chewing mechanism and a small brain, its skull looks like an ape's skull. It looks like a miniaturized gorilla," Simons said.
The new skull fits easily into a person's palm and is less than half the size of the 1966 skull. The researchers think it was from a female weighing perhaps 5.5 pounds (2.5 kg), while the earlier one was from a male more than twice as big.
They said this size difference between the sexes of this species is similar to that of gorillas.
Simons said that he previously overestimated its brain size based on features of the 1966 skull, which has a bigger snout and more pronounced crests. Those features now seem to be attributes of a male of the species.
Other aspects of its remains indicate it was branching off from its lemur-like ancestors.
For example, its skull indicates the brain's visual cortex was large, suggesting it had very good vision -- an important characteristic of higher primates. Its eye sockets also indicate it was active during the day. Many more primitive primates are nocturnal.
Hai specialk,quote:Op dinsdag 15 mei 2007 00:43 schreef SpecialK het volgende:
Grappig dat er in dit stukje een referentie wordt gemaakt naar de tanden van de schedel als zijnde "more apelike". Ik vraag me af of de verzwakking van onze kaken (want we hebben geen bijtkracht vergeleken met andere primaten) dus iets is wat tegelijkertijd met de grootte van de schedel is veranderd.
Zou de structuur van een grotere schedel in de weg zitten van de kaak ivbm het bot of de aanhechtingspunten of dikte van de spieren?
Epigenetica zou namelijk impliceren dat de moderne evolutionaire synthese incompleet of niet geheel correct is:quote:In Biology, epigenetics is the study of all heritable and potentially reversible changes in genome function that do not alter the nucleotide sequence within the DNA. When a cell undergoes an epigenetic change, it is the phenotype of the cell that is affected. Epigenetic events during embryo development lead to the differentiation of fetal cells. The combined processes of fetal development and cell differentiation are called epigenesis. The term is also sometimes used as a synonym for the closely related topic of chromatin remodeling.
bronquote:The philosophical implications of epigenetics have been discussed by scientists such as Eva Jablonka, Marion Lamb and Massimo Pigliucci, who cite epigenetic inheritance as one of a number of factors suggesting that the neo-darwinian synthesis of the early twentieth century is incomplete. Jablonka and Lamb suggest that the standard way of thinking about evolution, in terms of changes in the frequency of one or more isolated genes needs to be questioned, and that, contrary to long-held majority opinion, not all genetic variation is entirely random or blind - some may be regulated and partially directed and that the concept of heridity that is currently being used in evolutionary thinking is far too narrow. Pigliucci suggests, in Nature that If one accepts this bold, expanded version of heredity and evolution, it turns out that evolution can proceed very rapidly and phenotypic modification can precede genetic changes, and that changes at the genetic level will often simply stabilize adaptive modifications that are initiated through phenotypic plasticity, epigenetic control mechanisms, or behavioural and symbolic means; that this framework would greatly help to solve old problems in evolutionary biology, such as the origin of novel structures, and that the ultra-reductionist, gene-centred approach has (at least partially) failed.
The extent to which evolution operates at several different levels is the nub of Patrick Bateson's "friendly disagreement" with Richard Dawkins. In a critique of determinism Robert Winston suggests that epigenetic inheritance is an important factor in the inadequacy of the "selfish gene" and "DNA" metaphors.
de bron is wel de gratis kwaliteitskrant De Persquote:Op donderdag 24 mei 2007 08:34 schreef Invictus_ het volgende:
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Erm, nee. Neem die maar mee naar TRU.
Het zijn alleen geen echte vleugels: dat zijn namelijk uitgegroeide voorste ledematen. En deze kat heeft gewoon zijn voorpoten nog.quote:
Ik ga even muggenziften, maar wel met een doel. Ik zie namelijk te vaak misverstanden in evolutiediscussies onstaan door een verkeerd beeld van wat er met mutaties bedoeld wordt.quote:Op donderdag 24 mei 2007 08:31 schreef osho het volgende:
Chinese kat heeft vleugels
[afbeelding]
de vraag is natuurlijk in hoeverre dit geen photoshop ismaar anders is het best een leuke mutatie
ok, duidelijkquote:Op donderdag 24 mei 2007 17:59 schreef barthol het volgende:
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Ik ga even muggenziften, maar wel met een doel. Ik zie namelijk te vaak misverstanden in evolutiediscussies onstaan door een verkeerd beeld van wat er met mutaties bedoeld wordt.
Te vaak is het beeld dat een mutatie een fenotypische verandering is. Een lichamelijke bijzonderheid.
Eigenlijk net zo als die opmerking "maar anders is het best een leuke mutatie"
Het gesimplificeerde beeld van evolutie van evolutie wordt dan vervolgens een wereld waarin die "mutanten" via natuurlijke selectie met elkaar concureren via het principe van de "survival of the fittest". Maar bij evolutie wordt het accent door evolutionair biologen tegenwoordig veel meer op de genetica gelegd. Het bovenstaande beeld is verouderd en verre van compleet om de evolutie goed te begrijpen. Bij het begrip "mutatie" probeer ik wat puristisch te zijn en "Mutatie" en "het gevolg van een mutatie" strikt te scheiden. Een mutatie is puur een verandering in het DNA, Als een dier vreemde of nieuwe kenmerken gaat vertonen is het dier geen mutatie. Ook de lichamelijke kenmerken zijn niet een mutatie. Het kan wel "het gevolg" van een mutatie zijn. Een mutatie is slechts een verandering in het Dna, en dat met of zonder gevolgen voor hoe het dier eruitziet of functioneert.
Ik ben wat puristisch, maar ik merk vaak dat er in evolutiediscussies een miscommunicatie onstaat door verkeerde voorstellingen van wat er met mutaties bedoeld wordt. De opmerking in de quote vond ik een mooie gelegenheid om het nog een keer zo te verwoorden.
groet.
whahaquote:This week, the creationist Ken Ham and his organization, Answers in Genesis, are practicing the Big Lie.
Tja, het is de academische wereld die commentaar geeft op neo- (en old-school)creationisme. PZ is op moment ongeveer de Amerikaanse equivalent van Dawkins hoewel hij het zelf nog niet doorheeft.quote:Op zondag 27 mei 2007 22:40 schreef Ali_Kannibali het volgende:
Lekkere opening weer:
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whaha
* heel die text is echt ontzettend haatdragend zeg
quote:Remains of giant dinosaur found in China
By AUDRA ANG, Associated Press Writer
BEIJING - The remains of a giant, birdlike dinosaur as tall as the formidable tyrannosaur have been found in China, a surprising discovery that indicates a more complicated evolutionary process for birds than originally thought, scientists said Wednesday.
Fossilized bones uncovered in the Erlian Basin of northern China's Inner Mongolia region show that the specimen was about 26 feet long, 16 feet tall and weighed 3,000 pounds, said Xu Xing, a paleontologist at the Institute of Vertebrate Paleontology & Paleoanthropology in Beijing.
The height is comparable to the meat-eating tyrannosaurs. But the dinosaur, called Gigantoraptor elrianensis, also had a beak and slender legs and likely had feathers. It was 35 times larger than its likely close relation, the Caudiperyx, a small, feathered dinosaur species, Xu said.
That puts the Gigantoraptor's existence at odds with prevailing theories that dinosaurs became smaller as they evolved into birds and that bigger dinosaurs had less birdlike characteristics, he said.
"This is like having a mouse that is the size of a horse or cow," said Xu, who co-authored a paper on the finding published Thursday in the journal Nature. "It is very important information for us in our efforts to trace the evolution process of dinosaurs to birds. It's more complicated than we imagined."
The Caudiperyx and the Gigantoraptor belong to a group of dinosaurs called oviraptors, which tend to be human-sized or smaller. In recent years paleontologists have found turkey-sized, feathered representatives of the group, but they have never found anything close to the scale of Gigantoraptor.
"It's one of the last groups of dinosaurs that we would expect to be that big," said Mark Norell, curator of paleontology at the American Museum of Natural History in New York City.
But Philip Currie, a paleontologist at the University of Alberta, said the size of the Gigantoraptor would be a natural step in the evolutionary process of the oviraptors.
"Almost every group that has evolved has tended to evolve giant forms," Currie said.
Animals tend to become bigger with evolution because larger creatures have an easier time getting food, impressing potential mates and avoiding predators.
But size has disadvantages, too. Bigger animals need more food and territory. They have fewer offspring and reproduce less frequently than smaller animals do. That means they are particularly vulnerable when environmental conditions change, as they abruptly did about 65 million years ago. Just a few million years after Gigantoraptor evolved, it and every other dinosaur species on Earth became extinct.
On Wednesday, reporters were given a look at the Gigantoraptor's remains — two yellowing, rough-edged leg bones both a little over 3.2 feet long and believed to be those of a young adult.
It has not been determined whether the Gigantoraptor was a herbivore, which have small heads and long necks, or a carnivore, which have sharp claws. The dinosaur has both, Xu said.
Xu and his team, which discovered three other specimens in the fossil-rich Erlian Basin, were being interviewed by Japanese media in 2005 when they discovered the Gigantoraptor remains.
They had chosen a random site to illustrate how one of the previous fossils had been discovered and hit upon a bone while on camera, Xu said. The team originally thought that it belonged to a tyrannosaur because of its size, but realized upon examination that it was an oviraptor.
"It was an unexpected finding," Xu said.
___
Associated Press writer Matt Crenson in New York contributed to this story.
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