Evolutie. Deel XV

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The loci of evolution: how predictable is genetic evolution?
Stern, D.L. and Orgogozo, V. (2008)
Evolution Volume 62, Issue 9, Pages 2155-2177


Abstract
Is genetic evolution predictable? Evolutionary developmental biologists have argued that, at least for morphological traits, the answer is a resounding yes. Most mutations causing morphological variation are expected to reside in the cis-regulatory, rather than the coding, regions of developmental genes. This "cis-regulatory hypothesis" has recently come under attack. In this review, we first describe and critique the arguments that have been proposed in support of the cis-regulatory hypothesis. We then test the empirical support for the cis-regulatory hypothesis with a comprehensive survey of mutations responsible for phenotypic evolution in multicellular organisms. Cis-regulatory mutations currently represent approximately 22% of 331 identified genetic changes although the number of cis-regulatory changes published annually is rapidly increasing. Above the species level, cis-regulatory mutations altering morphology are more common than coding changes. Also, above the species level cis-regulatory mutations predominate for genes not involved in terminal differentiation. These patterns imply that the simple question "Do coding or cis-regulatory mutations cause more phenotypic evolution?" hides more interesting phenomena. Evolution in different kinds of populations and over different durations may result in selection of different kinds of mutations. Predicting the genetic basis of evolution requires a comprehensive synthesis of molecular developmental biology and population genetics.

Conclusion
In the absence of a population genetics framework, evolutionary developmental biologists have inferred from (1) our current understanding of gene regulatory networks, (2) our understanding of gene structure and function, and (3) the extensive conservation of developmental genes, that mutations in the cis-regulatory regions of developmental patterning genes are likely to underlie most of phenotypic evolution. However, no single argument proposed so far provides definitive proof that cis-regulatory mutations constitute the predominant cause of phenotypic evolution. By considering development and population genetics simultaneously, a survey of published data suggests that patterns of genetic evolution are not entirely obscured by historical contingency. Population genetics and development must be considered simultaneously to make sense of the data.

It may be unhelpful to pose the coding versus cis-regulatory debate as a quantitative question: do coding changes explain more of phenotypic evolution than cis-regulatory changes? It may be more productive to turn the question around and ask what kinds of phenotypic changes are expected from particular coding versus cis-regulatory changes in specific genes. As we show, patterns in the currently available data imply that morphological and physiological traits are caused by different frequencies of coding and cis-regulatory changes. This is consistent with our molecular understanding of how coding and cis-regulatory changes might influence physiology and morphology.

We also found that different spectra of evolutionarily relevant mutations segregate within populations and between species. Interspecific differences in morphology seem to be more often caused by cis-regulatory changes than intraspecific variation. This result is not predicted by a traditional neo-Darwinian view of the contribution of intraspecific variation to interspecific differences. Instead, it appears that evolution over longer time scales results in fixation of a specific subset of the genetic variation contributing to intraspecific phenotypic variation.

By fusing developmental and evolutionary genetics, evolutionary biologists may be able to predict, in a probabilistic sense, the mutations underlying phenotypic evolution. Fortunately, scientists are rapidly identifying the genetic causes of phenotypic evolution, providing abundant data for testing new predictions about the genetic basis of evolution.

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New Ant Species Discovered In The Amazon Likely Represents Oldest Living Lineage Of Ants

A new species of blind, subterranean, predatory ant discovered in the Amazon rainforest by University of Texas at Austin evolutionary biologist Christian Rabeling is likely a descendant of the very first ants to evolve.

The new ant is named Martialis heureka, which translates roughly to "ant from Mars," because the ant has a combination of characteristics never before recorded. It is adapted for dwelling in the soil, is two to three millimeters long, pale, and has no eyes and large mandibles, which Rabeling and colleagues suspect it uses to capture prey.

The ant also belongs to its own new subfamily, one of 21 subfamilies in ants. This is the first time that a new subfamily of ants with living species has been discovered since 1923 (other new subfamilies have been discovered from fossil ants).

Rabeling says his discovery will help biologists better understand the biodiversity and evolution of ants, which are abundant and ecologically important insects.

"This discovery hints at a wealth of species, possibly of great evolutionary importance, still hidden in the soils of the remaining rainforests," writes Rabeling and his co-authors in a paper reporting their recent discovery in the Proceedings of the National Academy of Sciences.

Rabeling collected the only known specimen of the new ant species in 2003 from leaf-litter at the Empresa Brasileira de Pesquisa Agropecuária in Manaus, Brazil.

He and his colleagues found that the ant was a new species, genus and subfamily after morphological and genetic analysis. Analysis of DNA from the ant's legs confirmed its phylogenetic position at the very base of the ant evolutionary tree.

Ants evolved over 120 million years ago from wasp ancestors. They probably evolved quickly into many different lineages, with ants specializing to lives in the soil, leaf-litter or trees, or becoming generalists.

"This discovery lends support to the idea that blind subterranean predator ants arose at the dawn of ant evolution," says Rabeling, a graduate student in the ecology, evolution and behavior program.

Rabeling does not suggest that the ancestor to all ants was blind and subterranean, but that these adaptations arose early and have persisted over the years.

"Based on our data and the fossil record, we assume that the ancestor of this ant was somewhat wasp-like, perhaps similar to the Cretaceous amber fossil Sphecomyrma, which is widely known as the evolutionary missing link between wasps and ants," says Rabeling.

He speculates that the new ant species evolved adaptations over time to its subterranean habitat (for example, loss of eyes and pale body color), while retaining some of its ancestor's physical characteristics.

"The new ant species is hidden in environmentally stable tropical soils with potentially less competition from other ants and in a relatively stable microclimate," he says. "It could represent a 'relict' species that retained some ancestral morphological characteristics."

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Op zondag 28 september 2008 19:28 schreef digitaLL het volgende:
In het volgende filmpje een experiment met een chimp. Hij onthoudt een reeks van 9 getallen willekeurig verspreid feilloos binnen een fractie van een seconde. Mensen hebben enkele seconden nodig en hebben met 5 getallen al moeite en doen het zeker niet foutloos.

The human ape 6/10

In een ander fragment van deze docu is ook te zien dat kinderen erg vatbaar zijn voor mythologie een nutteloze handeling bijvoorbeeld repeteren ze zonder kritisch te zijn, een chimp daarentegen doorziet dat en slaat zo'n handeling over.

The human ape 4/10
The human ape 5/10

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In an outing in the Georgia woods, Kanzi touched the symbols for "marshmallows" and "fire." "Given matches and marshmallows, Kanzi snapped twigs for a fire, lit them with the matches and toasted the marshmallows on a stick."

Paul Raffaele, at Savage-Rumbaugh's request, performed a Maori War Dance for the Bonobos. This dance includes thigh-slapping, chest-thumping, and hollering. Almost all the bonobos present interpreted this as an aggressive display, and reacted with loud screams, tooth-baring, and pounding the walls and floor. All but Kanzi, who remained perfectly calm, and conveyed in Bonobo language (interpreted by Savage-Rumbaugh to Raffaele) that he knew that no threat was meant, but that the performance should be apart from the other bonobos so as not to upset them. So a private performance in another room was successfully, peacefully and happily carried out.

Sue Savage-Rumbaugh has observed Kanzi in communication to his sister. In this experiment, Kanzi was kept in a separate room of the Great Ape Project and shown some yogurt. Kanzi started vocalizing the word "yogurt" in an unknown "language"; his sister, who could not see the yogurt, then pointed to the lexigram for yogurt.

Kanzi's accomplishments also include tool use and tool crafting. Kanzi is an accomplished stone tool maker and is quite proud of his ability to flake Oldowan style cutting knives. He learned this skill from Dr. Nick Toth, who is an anthropologist with the Stone Age Institute in Bloomington, Indiana. The stone knives Kanzi creates are very sharp and can cut animal hide and thick ropes.

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The Origin and Evolution of Religious Prosociality
Ara Norenzayan* and Azim F. Shariff

We examine empirical evidence for religious prosociality, the hypothesis that religions facilitate costly behaviors that benefit other people. Although sociological surveys reveal an association between self-reports of religiosity and prosociality, experiments measuring religiosity and actual prosocial behavior suggest that this association emerges primarily in contexts where reputational concerns are heightened.
Experimentally induced religious thoughts reduce rates of cheating and increase altruistic behavior among anonymous strangers. Experiments demonstrate an association between apparent profession of religious devotion and greater trust. Cross-cultural evidence suggests an association between the cultural presence of morally concerned deities and large group size in humans. We synthesize converging evidence from various fields for religious prosociality, address its specific boundary conditions, and point to unresolved questions and novel predictions.

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Conclusions, Outstanding Questions, and Future Directions

Many religious traditions around the world explicitly encourage the faithful to be unconditionally prosocial (1, 2); yet, theoretical considerations and empirical evidence indicate that religiously socialized individuals should be, and are, much more discriminating in their prosociality (2). Although empathy and compassion as social-bonding emotions do exist and may play a role in prosocial acts of religious and nonreligious individuals some of the time (41), there is little direct evidence to date that such emotions are systematically implicated in religious prosociality.

The preponderance of the evidence points to religious prosociality being a bounded phenomenon. Religion's association with prosociality is most evident when the situation calls for maintaining a favorable social reputation within the ingroup. When thoughts of morally concerned deities are cognitively salient, an objectively anonymous situation becomes nonanonymous and, therefore, reputationally relevant, or alternatively, such thoughts activate prosocial tendencies because of a prior mental association. This could occur when such thoughts are induced experimentally or in naturalistic religious situations, such as when people attend religious services or engage in ritual performance. This explains why the religious situation is more important than the religious disposition in predicting prosocial behavior.

Although religions continue to be powerful facilitators of prosociality in large groups, they are not the only ones. The cultural spread of reliable secular institutions, such as courts, policing authorities, and effective contract-enforcing mechanisms, although historically recent, has changed the course of human prosociality. Consequently, active members of modern secular organizations are at least as likely to report donating to charity as active members of religious ones (42). Supporting this conclusion, experimentally induced reminders of secular moral authority had as much effect on generous behavior in an economic game as reminders of God (27), and there are many examples of modern, large, cooperative, and not very religious societies (such as those in Western and Northern Europe), that, nonetheless, retain a great degree of intragroup trust and cooperation (43).

Any one study we have discussed can be subject to alternative accounts; therefore, specific evidence should be interpreted with caution. Nevertheless, convergent evidence is emerging from several disciplines using different methods and procedures that supply different pieces of the religious prosociality puzzle. Despite the recent scientific progress in explaining the effects of religion on prosociality, open and important questions remain. In particular, more research is needed to address the costliness of religious and nonreligious rituals, and few studies have attempted to quantify these costs in relation to prosocial behavior. The finding that religiosity evokes greater trust underscores the need for more experimental and theoretical research, including mathematical modeling, to establish the specific conditions under which costly religious commitment could evolve as a stable individual strategy and whether these models need to take into account intergroup competition. More broadly, the extent to which religion is implicated in human cooperation, and the precise sequence of evolutionary developments in religious prosociality, remain open to lively scientific debate. Further progress on these issues will require concerted collaboration among historians, archaeologists, social scientists, and evolutionary biologists.

In recent years, moral psychology has received a great deal of scientific attention (44), and although most of the studies reviewed here concern behavioral outcomes, the relation between religious prosociality and moral intuitions and reasoning is ripe for further investigation. More direct research on the possible role of prosocial motivations, such as empathy and compassion, in religious prosociality are needed. Finally, we have seen that religious prosociality is not extended indiscriminately; the "dark side" of within-group cooperation is between-group competition and conflict (45). The same mechanisms involved in ingroup altruism may also facilitate outgroup antagonism. This is an area of no small debate, but scientific attention is needed to examine precisely how individuals and groups determine who are the beneficiaries of religious prosociality, and who its victims.

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Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens
Nitzan Mekel-Bobrov,1,2 Sandra L. Gilbert,1 Patrick D. Evans,1,2 Eric J. Vallender,1,2 Jeffrey R. Anderson,1 Richard R. Hudson,3 Sarah A. Tishkoff,4 Bruce T. Lahn1*

The gene ASPM (abnormal spindle-like microcephaly associated) is a specific regulator of brain size, and its evolution in the lineage leading to Homo sapiens was driven by strong positive selection. Here, we show that one genetic variant of ASPM in humans arose merely about 5800 years ago and has since swept to high frequency under strong positive selection. These findings, especially the remarkably young age of the positively selected variant, suggest that the human brain is still undergoing rapid adaptive evolution

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Recent acceleration of human adaptive evolution
John Hawks, Eric T. Wang, Gregory M. Cochran, Henry C. Harpending , and Robert K. Moyzis

Genomic surveys in humans identify a large amount of recent positive selection. Using the 3.9M HapMap SNP dataset, we found that selection has accelerated greatly during the last 40,000 years. We tested the null hypothesis that the observed age distribution of recent positively selected linkage blocks is consistent with a constant rate of adaptive substitution during human evolution. We show that a constant rate high enough to explain the number of recently selected variants would predict (1) site heterozygosity at least tenfold lower than is observed in humans, (2) a strong relationship of heterozygosity and local recombination rate, which is not observed in humans, (3) an implausibly high number of adaptive substitutions between humans and chimpanzees, and (4) nearly 100 times the observed number of high-frequency LD blocks. Larger populations generate more new selected mutations, and we show the consistency of the observed data with the historical pattern of human population growth. We consider human demographic growth to be linked with past changes in human cultures and ecologies. Both processes have contributed to the extraordinarily rapid recent genetic evolution of our species.

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Researchers have found a possible new route taken by early modern humans as they expanded out of Africa to colonise the rest of the world.

A study published in the journal PNAS proposes a "wet corridor" through Libya for ancient human migrations.
Rivers once flowed from the central Saharan watershed all the way to the Mediterranean, the team explains.
This might have enabled modern humans to spread beyond their ancestral homeland about 120,000 years ago. The Sahara then covered most of North Africa, as it does now. So it would have presented a formidable obstacle for early modern humans wishing to cross from the south to the north of the continent.

Researchers had previously focused on the Nile Valley as the principal route of dispersal into other continents by early representatives of our species. Previous data show there was increased rainfall across the southern part of the Sahara between 130,000 and 170,000 years ago; in a gap between Ice Ages known as the last interglacial period.

The researchers, from the universities of Bristol, Southampton, Oxford, Hull and Tripoli in Libya, investigated whether these wetter conditions had reached a lot further north than previously thought. Radar images from space revealed fossil river channels crossing the Sahara in Libya, flowing north from the central Saharan watershed to the Mediterranean coast. Using geochemical tests, the scientists showed the channels were active during the last interglacial. This would have created vital water courses across an otherwise arid region, the researchers write in PNAS.

The central Saharan watershed is a range of volcanic mountains formerly considered to be the limit of this wetter region. Researchers analysed the forms, or isotopes, of different chemical elements in snail shells from two sites in the fossil river channels and from the shells of planktonic microfossils in the Mediterranean.
Despite being hundreds of kilometres from the volcanic rocks of the Saharan watershed, the tests revealed a distinct volcanic signature to these shells, which was quite different to rocks from surrounding sites. The scientists concluded that water flowing from the volcanic mountains of the central Sahara was the only possible source of this signature.

"It's a possible route that the early modern humans could have taken," lead author Anne Osborne, from the earth sciences group at Bristol, told BBC News. Similarities in the style of stone tools being made in Chad and Sudan with those manufactured in Libya during this key period, lend the theory some support, say the scientists. "We now need to focus archaeological fieldwork around the large drainage channels an palaeo-lakes to test these ideas," said co-author Dr Nick Barton, from the University of Oxford. Although it is unclear which routes they took to get there, Homo sapiens had reached the Levant by around 100,000 years ago, where their remains are known from Es Skhul and Qafzeh in Israel.

However, this appears to have been an early, failed foray outside Africa by modern humans. By 75,000 years ago, Neanderthals had replaced our species in the region.

Then, about 45,000 years ago, modern humans reoccupied the area. Genetic evidence suggests that populations living outside Africa today are the descendents of a migration which originated in the east of the continent between 60-70,000 years ago. Some of these pioneers probably crossed the Red Sea at the Bab-el-Mandab straits, taking them from the Horn of Africa across to the Arabian Peninsula.

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Zhang, F. et al. (2008) A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers. Nature, 455, 1105-1108.

Recent coelurosaurian discoveries have greatly enriched our knowledge of the transition from dinosaurs to birds, but all reported taxa close to this transition are from relatively well known coelurosaurian groups1, 2, 3. Here we report a new basal avialan, Epidexipteryx hui gen. et sp. nov., from the Middle to Late Jurassic of Inner Mongolia, China. This new species is characterized by an unexpected combination of characters seen in several different theropod groups, particularly the Oviraptorosauria. Phylogenetic analysis shows it to be the sister taxon to Epidendrosaurus 4, 5, forming a new clade at the base of Avialae6. Epidexipteryx also possesses two pairs of elongate ribbon-like tail feathers, and its limbs lack contour feathers for flight. This finding shows that a member of the avialan lineage experimented with integumentary ornamentation as early as the Middle to Late Jurassic, and provides further evidence relating to this aspect of the transition from non-avian theropods to birds.

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Op zondag 26 oktober 2008 17:52 schreef Aslama het volgende:
Vertel mij maar de evolutie van het DNA van niets tot een paar miljard baseparen die samen de code vormen voor een species. Ja in je eigen woord :-)
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Op maandag 27 oktober 2008 19:18 schreef Aslama het volgende:

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Beschrijf dan alleen van wat al zo duidelijk is van het bewijs van de evolutie op het gebied van het DNA. Dit moet toch niet zo moeilijk zijn daar de evolutie overduidelijk is bewezen.