http://knack.rnews.be/nie(...)45-article44376.htmlquote:"De mens is niet geprogrammeerd tot zelfzucht"
30/12/2009 09:00
Dit is een tijd voor empathie, betoogt Frans de Waal, de grote 'mensaapkundige' die in 2007 door het weekblad Time werd uitgeroepen tot een van de honderd invloedrijkste mensen van deze wereld, in zijn nieuwe boek. Niet hoewel, maar juist omdát we (zoog)dieren zijn.
DE WAAL: Wat ik in dit boek probeer te doen is aan te tonen dat wij mensen van nature dus in ieder geval empathie hébben, en dat we dat delen met heel veel zoogdieren.
Dat betekent ook dat als je een samenleving wilt die de menselijke natuur recht doet daar empathie en solidariteit bij horen, want die zijn deel van wie en wat we zijn. Ik kan niet preciezer zeggen hoe je dat dan aanpakt. Dat zijn maatschappelijke beslissingen, en dat horen ze ook te zijn.
Ik geloof niet dat je als bioloog kunt voorschrijven hoe de samenleving in elkaar gezet moet worden. Je kunt alleen wat aanwijzingen geven, en je moet je hoeden voor de naturalistische drogreden: dat iets deel is van de natuur, betekent nog niet dat het dus per definitie goed is. Maar ik verzet me tegen het idee dat vaak naar voren wordt gebracht, vooral in Amerika, dat wij van nature zelfzuchtig en competitief zijn, en alléén maar zelfzuchtig en competitief.
U werkt sinds 1981 in de VS. Merkt u daar andere reacties, met name uit religieuze hoek, op uw werk dan in Europa?
DE WAAL: Nou, creationisten zullen mijn boeken nauwelijks lezen, vermoed ik. Maar de Amerikanen zijn over het algemeen heel geïnteresseerd in mens-diervergelijkingen. Ze zijn daar de laatste twintig jaar veel opener in geworden, net zoals de Europeanen. Als je twintig jaar geleden zei: 'Het verschil tussen man en vrouw is genetisch bepaald' - o man, dat was een ellende in die tijd! Tegenwoordig kun je dat zeggen. En je kunt menselijk gedrag met apengedrag vergelijken. Destijds was dat nogal problematisch. Je kreeg al snel het verwijt sentimenteel te zijn, of in ieder geval niet objectief. Met die vergelijking op zich hebben trouwens ook creationisten meestal weinig problemen.
Maar ze hebben toch een onoverkomelijk probleem met de evolutionaire basis waarvan u bij die vergelijking uitgaat?
DE WAAL: Volgens mij ligt het toch anders dan bijvoorbeeld Richard Dawkins (Brits etholoog en vurig verdediger van de evolutietheorie, nvdr.) en dat soort mensen denken. Zij denken dat je creationisten ervan moet proberen te overtuigen dat het bewijsmateriaal voor de evolutie heel groot is. Wat ook zo ís, dat weet iedereen. Dawkins probeert dus rationeel, met bewijsmateriaal, de creationistische tegenstander ervan te overtuigen dat wij niet samen met de dino's op de aarde hebben rondgelopen. Maar volgens mij gaat het hier uiteindelijk niet om rationaliteit of bewijsmateriaal. Mensen in Amerika die echt gelovig zijn denken dat als we accepteren dat wij niet door God zijn geschapen dat automatisch betekent dat we álles kunnen doen en alle normen en waarden meteen het raam uit vliegen. Ze zijn bang dat het aanvaarden van de evolutietheorie tot moreel verval leidt. Het gaat hier om een heel diep gevoel van ongemak bij de gedachte dat wij het product van toevalsprocessen zijn.
Kunt u het nog wel vinden met Dawkins?
DE WAAL: Mijn ideeën zijn niet in strijd met Dawkins' ideeën, daar gaat het niet om. Maar als je het hebt over 'het zelfzuchtige gen', om Dawkins' beruchte metafoor aan te halen, dan denken heel veel mensen automatisch dat dat betekent dat wij geprogrammeerd zijn tot zelfzucht. En daar verzet ik me tegen. Die interpretatie is niet noodzakelijk wat Dawkins zelf bedoelde - integendeel zelfs - maar hij heeft het er wel naar gemaakt dát hij zo algemeen verkeerd begrepen wordt.
Herman Jacobs
Was weer een erg aardig boek van de Waal, zoals gebruikelijk.quote:Op woensdag 30 december 2009 19:29 schreef zakjapannertje het volgende:
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http://knack.rnews.be/nie(...)45-article44376.html
Nuquote:'Levensloze' eiwitten kunnen evolueren
Uitgegeven: 4 januari 2010 08:20
AMSTERDAM – Amerikaanse wetenschappers hebben ontdekt dat eiwitdeeltjes zonder genetisch materiaal op dezelfde manier kunnen evolueren als hogere organismen.
De wetenschappers van het Scripps Research Institute onderzochten de evolutie van prionen.
Dat zijn eiwitdeeltjes zonder enige DNA-structuur die ernstige infectieziektes kunnen veroorzaken in de hersenen.
Bij een experiment in het laboratorium verplaatsten de onderzoekers prionen uit hersencellen naar andere gecultiveerde celomgevingen.
Al snel bleek dat de eiwitdeeltjes zich ondanks de afwezigheid van DNA razendsnel aanpasten aan hun omgeving. Er ontstonden nieuwe soorten prionen die veel beter in de nieuwe cellen overleefden dan prionen die rechtstreeks uit de hersencellen kwamen.
Universeel
De resultaten van het experiment zijn gepubliceerd in het wetenschappelijk tijdschrift Science.
Volgens de onderzoekers bewijst het experiment dat prionen op dezelfde manier kunnen evolueren als virussen, ondanks het feit dat de eiwitdeeltjes niet zijn opgebouwd uit DNA of RNA.
“Dit betekent dat het patroon van evolutie zoals het werd beschreven door Darwin universeel is”, zo verklaart hoofdonderzoeker Charles Weissman op BBC News.
Nucleïnezuur
“In virussen wordt mutatie gelinkt aan veranderingen in de volgorde van het nucleïnezuur. Maar de evolutionaire aanpassing die we zien bij dit experiment voltrekt zich op het niveau van prionen en eiwitten”, aldus Weissman.
“Het is nu duidelijk dat er geen nucleïnezuur nodig is voor het proces van evolutie."
15-01-2010quote:Op donderdag 14 januari 2010 22:30 schreef ExperimentalFrentalMental het volgende:
14-01-2010
Een Y-splitsing in de stamboom
NY Timesquote:Genome Study Provides a Census of Early Humans
From the composition of just two human genomes, geneticists have computed the size of the human population 1.2 million years ago from which everyone in the world is descended.
They put the number at 18,500 people, but this refers only to breeding individuals, the “effective” population. The actual population would have been about three times as large, or 55,500.
Comparable estimates for other primates then are 21,000 for chimpanzees and 25,000 for gorillas. In biological terms, it seems, humans were not a very successful species, and the strategy of investing in larger brains than those of their fellow apes had not yet produced any big payoff. Human population numbers did not reach high levels until after the advent of agriculture.
Geneticists have long known that the ancestors of modern humans numbered as few as 10,000 at some time in the last 100,000 years. The critically low number suggested that some catastrophe, like disease or climate change induced by a volcano, had brought humans close to the brink of extinction.
If the new estimate is correct, however, human population size has been small and fairly constant throughout most of the last million years, ruling out the need to look for a catastrophe.
The estimate, reported in the issue on Tuesday of The Proceedings of the National Academy of Sciences, was made by a team of population geneticists at the University of Utah led by Chad D. Huff and Lynn B. Jorde.
The human population a million years ago was represented by archaic species like Homo ergaster in Africa and Homo erectus in East Asia. The Utah team says its estimate of 18,500 implies “an unusually small population for a species spread across the entire Old World.”
But that estimate would apply to the worldwide population only if there were inbreeding between the humans on the different continents. If not, and if modern humans are descended from just one of these populations, like Homo ergaster in Africa, then the estimate would apply only to that.
Richard G. Klein, a paleoanthropologist at Stanford, said it was hard to believe the population from which modern humans are descended was as small as 18,500 “unless they were geographically restricted to Africa or a small part of it.”
There is no independent way of assessing a genetics-based estimate of population size at this period, Dr. Klein said, although archaeologists have developed ways of assessing ancient populations of more recent times.
The Utah team based its estimate on the genetic variation present in two complete human genomes, one prepared by the government’s human genome project and the other by J. Craig Venter, the genome sequencing pioneer. The government decoded a single copy of a mosaic genome derived from a medley of people, apparently of European and Asian origin. Dr. Venter decoded both copies of his own genome, the one inherited from his father and the one from his mother.
The Utah team thus had three genomes to work with and looked at ancient elements known as Alu insertions, the youngest class of which appeared in the human genome around a million years ago. The amount of variation seen in the DNA immediately surrounding the Alu insertions gave a measure of the size of human population at that time.
Their estimate agrees almost exactly with an earlier one, also based on Alu insertions but with sparser data. The insertions tag ancient regions of the genome that are unaffected by the recent growth in population, Dr. Huff said.
quote:Draghi, J.A. et al. (2010) Mutational robustness can facilitate adaptation. Nature, 463, 463, 353-355.
Robustness seems to be the opposite of evolvability. If phenotypes are robust against mutation, we might expect that a population will have difficulty adapting to an environmental change, as several studies have suggested1, 2, 3, 4. However, other studies contend that robust organisms are more adaptable5, 6, 7, 8. A quantitative understanding of the relationship between robustness and evolvability will help resolve these conflicting reports and will clarify outstanding problems in molecular and experimental evolution, evolutionary developmental biology and protein engineering. Here we demonstrate, using a general population genetics model, that mutational robustness can either impede or facilitate adaptation, depending on the population size, the mutation rate and the structure of the fitness landscape. In particular, neutral diversity in a robust population can accelerate adaptation as long as the number of phenotypes accessible to an individual by mutation is smaller than the total number of phenotypes in the fitness landscape. These results provide a quantitative resolution to a significant ambiguity in evolutionary theory.
[..]
The relationship between robustness and evolvability is complex because robust populations harbour a large diversity of neutral genotypes that may be important in adaptation9, 10, 11. Although neutral mutations do not change an organism’s phenotype, they may nevertheless have epistatic consequences for the phenotypic effects of subsequent mutations12, 13, 14, 15, 16, 17, 18. In particular, a neutral mutation can alter an individual’s ‘phenotypic neighbourhood’, that is, the set of distinct phenotypes that the individual can access through a further mutation. Pioneering studies based on RNA folding and network dynamics suggest that genotypes expressing a particular phenotype are often linked by neutral mutations into a large neutral network, and that members of a neutral network differ widely in their phenotypic neighbourhoods1, 19, 20, 21. Numerous studies have documented the importance of neutral variation in allowing a population to access adaptive phenotypes5, 17, 18, 22, 23, 24, and neutral networks have consequently been proposed to facilitate adaptation9, 10, 11.
Here we analyse the relationship between robustness and evolvability using a population genetics model that specifies statistical properties of the fitness landscape.
[..]
Our results reveal a complex relationship between robustness and evolvability. In some situations, increasing robustness will decrease evolvability, whereas in other situations it will accelerate adaptation. The latter phenomenon can occur only when the number of phenotypes accessible to an individual, K, is smaller than the total number of alternative phenotypes in the landscape, P.
Bronartikel ScienceDailyquote:New Theory on the Origin of Primates
ScienceDaily, (jan 20 2010)
A new model for primate origins is presented in Zoologica Scripta, published by the Norwegian Academy of Science and Letters and The Royal Swedish Academy of Sciences. The paper argues that the distributions of the major primate groups are correlated with Mesozoic tectonic features and that their respective ranges are congruent with each evolving locally from a widespread ancestor on the supercontinent of Pangea about 185 million years ago.
Michael Heads, a Research Associate of the Buffalo Museum of Science, arrived at these conclusions by incorporating, for the first time, spatial patterns of primate diversity and distribution as historical evidence for primate evolution. Models had previously been limited to interpretations of the fossil record and molecular clocks.
"According to prevailing theories, primates are supposed to have originated in a geographically small area (center of origin) from where they dispersed to other regions and continents" said Heads, who also noted that widespread misrepresentation of fossil molecular clocks estimates as maximum or actual dates of origin has led to a popular theory that primates somehow crossed the globe and even rafted across oceans to reach America and Madagascar.
In this new approach to molecular phylogenetics, vicariance, and plate tectonics, Heads shows that the distribution ranges of primates and their nearest relatives, the tree shrews and the flying lemurs, conforms to a pattern that would be expected from their having evolved from a widespread ancestor. This ancestor could have evolved into the extinct Plesiadapiformes in north America and Eurasia, the primates in central-South America, Africa, India and south East Asia, and the tree shrews and flying lemurs in South East Asia.
Divergence between strepsirrhines (lemurs and lorises) and haplorhines (tarsiers and anthropoids) is correlated with intense volcanic activity on the Lebombo Monocline in Africa about 180 million years ago. The lemurs of Madagascar diverged from their African relatives with the opening of the Mozambique Channel (160 million years ago), while New and Old World monkeys diverged with the opening of the Atlantic about 120 million years ago.
"This model avoids the confusion created by the center of origin theories and the assumption of a recent origin for major primate groups due to a misrepresentation of the fossil record and molecular clock divergence estimates" said Michael from his New Zealand office. "These models have resulted in all sorts of contradictory centers of origin and imaginary migrations for primates that are biogeographically unnecessary and incompatible with ecological evidence."
The tectonic model also addresses the otherwise insoluble problem of dispersal theories that enable primates to cross the Atlantic to America, and the Mozambique Channel to Madagascar although they have not been able to cross 25 km from Sulawesi to Moluccan islands and from there travel to New Guinea and Australia.
Heads acknowledged that the phylogenetic relationships of some groups such as tarsiers, are controversial, but the various alternatives do not obscure the patterns of diversity and distribution identified in this study.
Biogeographic evidence for the Jurassic origin for primates, and the pre-Cretaceous origin of major primate groups considerably extends their divergence before the fossil record, but Heads notes that fossils only provide minimal dates for the existence of particular groups, and there are many examples of the fossil record being extended for tens of millions of years through new fossil discoveries.
The article notes that increasing numbers of primatologists and paleontologists recognize that the fossil record cannot be used to impose strict limits on primate origins, and that some molecular clock estimates also predict divergence dates pre-dating the earliest fossils. These considerations indicate that there is no necessary objection to the biogeographic evidence for divergence of primates beginning in the Jurassic with the origin of all major groups being correlated with plate tectonics.
http://knack.rnews.be/nie(...)45-article45310.htmlquote:Unieke fauna in Madagaskar spoelde aan
21/01/2010 09:00
De unieke fauna in Madagaskar, waaronder de exotische lemuren, dreef via natuurlijke vegetatie over zee naar het eiland, zeggen wetenschappers in het magazine 'Nature'.
De herkomst van de unieke lemuren, civetkatten, mangoesten en knaagdieren op Madagaskar is lang een mysterie geweest. Maar onderzoekers van de Purdue University in Indiana (VS) en de University of Hong Kong hebben nu ontdekt dat de voorouders van deze dieren het eiland zo'n 60 miljoen jaar geleden bereikten via drijvende stukken vegetatie, zoals boomstammen, die door de zeestromen werden meegevoerd.
'Drijftheorie'
70 jaar geleden suggereerde de paleontoloog George Gaylord Simpson al een gelijkaardige 'drijftheorie'. Dat zou verklaren waarom er enerzijds zo weinig diersoorten op het eiland aanwezig zijn en er anderzijds geen grote diersoorten voorkomen, omdat die te zwaar waren om zo'n reis te ondernemen.
Maar de theorie werd door wetenschappers lang gecontesteerd omdat de zeestromen rond het eiland van het eiland zijn weggericht.
Uit een computersimulatie blijkt echter dat de zeestromen vroeger heel anders waren. In de periode waarin de dieren aan land kwamen, zo'n 60 miljoen jaar geleden, waren de stromingen naar het land toe gericht. 20 miljoen jaar geleden verschoven de tektonische platen die Afrika en Madagaskar dragen, naar het noorden, waardoor de stroming veranderde.
Madagaskar brak 120 miljoen jaar geleden af van het Afrikaanse vasteland. Door zijn geïsoleerde ligging ontwikkelde het eiland een bijzondere biodiversiteit. Meer dan 90 procent van de zoogdieren, reptielen en amfibieën komen nergens anders voor.
Hele artikelquote:Evolution of Adaptive Behaviour in Robots by Means of Darwinian Selection
Ever since Cicero's De Natura Deorum ii.34., humans have been intrigued by the origin and mechanisms underlying complexity in nature. Darwin suggested that adaptation and complexity could evolve by natural selection acting successively on numerous small, heritable modifications. But is this enough? Here, we describe selected studies of experimental evolution with robots to illustrate how the process of natural selection can lead to the evolution of complex traits such as adaptive behaviours. Just a few hundred generations of selection are sufficient to allow robots to evolve collision-free movement, homing, sophisticated predator versus prey strategies, coadaptation of brains and bodies, cooperation, and even altruism. In all cases this occurred via selection in robots controlled by a simple neural network, which mutated randomly.
Genes do not specify behaviours directly but rather encode molecular products that lead to the development of brains and bodies through which behaviour is expressed. An important task is therefore to understand how adaptive behaviours can evolve by the mere process of natural selection acting on genes that do not directly code for behaviours. A spectacular demonstration of the power of natural selection comes from experiments in the field of evolutionary robotics [1],[2], where scientists have conducted experimental evolution with robots. Evolutionary robotics has also been advocated as a method to automatically generate control systems that are comparatively simpler or more efficient than those engineered with other design methods because the space of solutions explored by evolution can be larger and less constrained than that explored by conventional engineering methods [3]. In this essay we will examine key experiments that illustrate how, for example, robots whose genes are translated into simple neural networks can evolve the ability to navigate, escape predators, coadapt brains and body morphologies, and cooperate. We present mostly—but not only—experimental results performed in our laboratory, which satisfy the following criteria. First, the experiments were at least partly carried out with real robots, allowing us to present a video showing the behaviours of the evolved robots. Second, the robot's neural networks had a simple architecture with no synaptic plasticity, no ontogenetic development, and no detailed modelling of ion channels and spike transmission. Third, the genomes were directly mapped into the neural network (i.e., no gene-to-gene interaction, time-dependent dynamics, or ontogenetic plasticity). By limiting our analysis to these studies we are able to highlight the strength of the process of Darwinian selection in comparable simple systems exposed to different environmental conditions. There have been numerous other studies of experimental evolution performed with computer simulations of behavioural systems. Reviews of these studies can be found in [4]–[6]. Furthermore, artificial evolution has also been applied to disembodied digital organisms living in computer ecosystems, such as Tierra [7] and Avida [8], to address questions related to gene interactions [9], evolution of complexity [10], and mutation rates [11],[12].
bronquote:Seven habits of highly successful toads
Toads are an evolutionary success story. In a relatively short span of time, they diversified into around 500 species and spread to every continent except Antarctica. Now, Ines van Bocxlaer from Vrije University has uncovered the secrets of their success. By comparing the most home-bound toads with the most invasive ones, she has outlined seven qualities that enabled these amphibians to conquer the world. In a common ancestor, these seven traits came together to create an eighth - a pioneer's skill are colonising new habitats.
Some, like the harlequin toads, are restricted to such narrow tracts of land that they are vulnerable to extinction. Others, like the infamous cane toads, are highly invasive and notoriously resistant to extinction despite the best efforts of Australians and their sporting equipment. This diversity of lifestyles allowed Bocxlaer to search for characteristics shared by the most pioneering of toad species.
She compared over 228 species, representing just under half of all the known toads, and constructed a family tree that charts their relationships. She showed, as others before have suggested, that the family's fortunes kicked off in South America, around 35-40 million years ago. This was the start of their global invasion.
Seven qualities make for wide-ranging toads. For a start, the adults don't have the typical amphibian dependency on constant water or humidity. They have skins that can cope with the drier side of life, giving them a chance to seek out new habitats away from the safety net of moist environments. Secondly, they tend to have fat deposits near their groin, which act as a back-up energy source when food is scarce. Thirdly, they tend to be larger (meaning at least 5 centimetres in length), which also helps to conserve water. Larger animals have larger bladders so they retain more water, and they lose less of it because they have small surface areas for their size.
Fourthly, the most wide-ranging species have parotid glands, large sacs that are usually armed with poisons called bufotoxins. Those of the cane toads have claimed the lives of many would-be predators, and even some humans. The defensive benefits are obvious but they also help toads to, once again, break their water habit. The glands secrete molecules that are extremely attracted to water, allowing the animals to store large amounts in the dry season.
The final three traits all affect the toads' reproductive life. Some species have to lay their eggs in very specific locations. But the widest-ranging ones opportunistically lay in all sorts of environments as long as there is some water, such as the brief puddles that form during sporadic rainfall. Pioneering species also tend to have tadpoles that get their food from their environment, rather than from yolk or other food sources packaged by their parents. Finally, toads with the largest egg clutches (up to 45,000 in the great plains toad) are more widely distributed than those that lay few eggs, like the flathead toads that only lay five.
By their powers combined, these seven attributes make a toad optimally poised to expand its range. By mapping the presence of these traits across the toad family tree, Bocxlaer showed that they slowly accumulated in the earliest toads. The point where all seven had been checked off the list coincided with the dramatic expansion of the dynasty out of South America and into other continents.
As these ancestral species hopped across the world, so they diversified into new forms. As the toads reached new continents and colonised new niches, they rapidly gave rise to new species. In the Old World, several lineages independently lost their ancestors' globe-trotting abilities, in favour of being more specialised and locally adapted.
But many retained the pioneering qualities. Today, many toads still have all seven traits to the extent that even distantly related species look very similar. They're relatively large, land-living animals with fat deposits and parotid glands, and they opportunistically lay large clutches of eggs that hatch into independent tadpoles. That's certainly a fair description of the cane toad. Bocxlaer's study shows that this pest's remarkable skill at invading Australia was rooted deep in its ancestry, a "remnant of the period when toads colonised the world".
http://www.news.com.au/en(...)frfou0-1225835778798quote:Dr Satoshi Kanazawa, an evolutionary psychologist from the London School of Economics and Political Science, said the smarter a man is, the less likely he is to cheat on his partner.
His theory is based on the assertion that through evolutionary history, men have always been "mildly polygamous".
That has changed today, however, and Dr Kanazawa explained that entering a sexually exclusive relationship is an 'evolutionarily novel' development for them.
According to his theory, intelligent people are more likely to adopt what in evolutionary terms are new practices - to become "more evolved".
Therefore, in the case of fidelity, men who cannot adapt and end up succumbing to temptation and cheating are likely to be more stupid.
"The theory predicts that more intelligent men are more likely to value sexual exclusivity than less intelligent men," he explained.
According to his theory, the link between fidelity and intelligence does not apply to women because they have always been expected to be faithful to one mate - even in polygamous societies.
Naturequote:Changes in Hox genes’ structure and function during the evolution of the squamate body plan
Hox genes are central to the specification of structures along the anterior–posterior body axis1, 2, and modifications in their expression have paralleled the emergence of diversity in vertebrate body plans3, 4. Here we describe the genomic organization of Hox clusters in different reptiles and show that squamates have accumulated unusually large numbers of transposable elements at these loci5, reflecting extensive genomic rearrangements of coding and non-coding regulatory regions. Comparative expression analyses between two species showing different axial skeletons, the corn snake and the whiptail lizard, revealed major alterations in Hox13 and Hox10 expression features during snake somitogenesis, in line with the expansion of both caudal and thoracic regions. Variations in both protein sequences and regulatory modalities of posterior Hox genes suggest how this genetic system has dealt with its intrinsic collinear constraint to accompany the substantial morphological radiation observed in this group.
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