intellectual vanities… about close to everything

Egyptian perfume bottle. Could product branding have begun in ancient Egypt? (Credit: iStockphoto)

Prehistories of Commodity Branding

by David Wengrow

Commodity branding has been characterized as the distinguishing cultural move of late capitalism and is widely viewed as a historically distinctive feature of the modern global economy. The brand’s rise to prominence following the Industrial Revolution and the attendant shift of corporate enterprise towards the dissemination of image-based products have been further cited as contributing to the erosion of older forms of identity such as those based on kinship and class. However, comparisons between recent forms of branding and much earlier modes of commodity marking associated with the Urban Revolution of the fourth millennium BC suggest that systems of branding address a paradox common to all economies of scale and are therefore likely to arise (and to have arisen) under a wide range of ideological and institutional conditions, including those of sacred hierarchies and stratified states. An examination of the material and cognitive properties of sealing practices and the changing functions of seals in their transition from personal amulets to a means of labeling mass-produced goods helps to unpack the interlocking (pre)histories of quality control, authenticity, and ownership that make up the modern brand.

Scientists at the University of Reading have discovered that languages change and evolve in rapid bursts rather than in a steady pattern. The research investigates thousands of years of language evolution, and looks at the way in which languages split and evolve. It has long been accepted that the desire for a distinct social identity may cause languages to change quickly, but it has not previously been known whether such rapid bursts of change are a regular feature of the evolution of human language.

The findings show that initially, the basic vocabulary of newly formed languages develops and changes quite quickly, and this is then followed by longer periods of slower and gradual change.

Rapid bursts of change at the time of language splitting are important processes in language evolution, and the research has found that these account for between 10 and 33 % of the total divergence amongst the basic vocabularies of the language groups studied. The research used data to construct evolutionary tree diagrams to explore the relationships between languages. The diagrams describe the separate paths of evolution leading from a common ancestral language to a set of distinct languages at the tips of the tree.

Professor Mark Pagel from the University of Reading said “Our research suggests that rapid bursts of change occur in languages, and this reflects a human ability to adjust languages at critical times of cultural evolution, such as during the emergence of new and rival groups.

The emergence of American English took place when the American English Dictionary was introduced by Noah Webster. He insisted that ‘as an independent nation, our honor requires us to have a system of our own, in language as well as Government’. This illustrates that language is not only used as a means of communication, but it is also important for social functions, including promoting group identity and unity.”
Science 1 February 2008: 588 DOI: 10.1126/science.1149683
Languages Evolve in Punctuational Bursts
Quentin D. Atkinson,^1* Andrew Meade,¹ Chris Venditti,¹ Simon J. Greenhill,² Mark Pagel^1,3

Linguists speculate that human languages often evolve in rapid or punctuational bursts, sometimes associated with their emergence from other languages, but this phenomenon has never been demonstrated. We used vocabulary data from three of the world’s major language groups—Bantu, Indo-European, and Austronesian—to show that 10 to 33% of the overall vocabulary differences among these languages arose from rapid bursts of change associated with language-splitting events. Our findings identify a general tendency for increased rates of linguistic evolution in fledgling languages, perhaps arising from a linguistic founder effect or a desire to establish a distinct social identity.

¹ School of Biological Sciences, University of Reading, Reading RG6 6AS, UK.
² Department of Psychology, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
³ Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.

^* Present address: Institute of Cognitive and Evolutionary Anthropology, University of Oxford, Oxford OX2 6QS, UK.

To whom correspondence should be addressed. E-mail: m.pagel@reading.ac.uk

Researchers have discovered genetic evidence that human evolution is speeding up — and has not halted or proceeded at a constant rate, as had been thought — indicating that humans on different continents are becoming increasingly different.

“We aren’t the same as people even 1,000 or 2,000 years ago,” says University of Utah anthropologist Henry Harpending. That might explain, for example, part of the difference between Viking invaders and their peaceful Swedish descendants. (Credit: iStockphoto/Manuel Velasco)

“We used a new genomic technology to show that humans are evolving rapidly, and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago,” says research team leader Henry Harpending, a distinguished professor of anthropology at the University of Utah.

Harpending says there are provocative implications from the study, published online Monday, Dec. 10 in the journal Proceedings of the National Academy of Sciences:

– “We aren’t the same as people even 1,000 or 2,000 years ago,” he says, which may explain, for example, part of the difference between Viking invaders and their peaceful Swedish descendants. “The dogma has been these are cultural fluctuations, but almost any temperament trait you look at is under strong genetic influence.”

– “Human races are evolving away from each other,” Harpending says. “Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity.” He says that is happening because humans dispersed from Africa to other regions 40,000 years ago, “and there has not been much flow of genes between the regions since then.”

“Our study denies the widely held assumption or belief that modern humans [those who widely adopted advanced tools and art] appeared 40,000 years ago, have not changed since and that we are all pretty much the same. We show that humans are changing relatively rapidly on a scale of centuries to millennia, and that these changes are different in different continental groups.”

The increase in human population from millions to billions in the last 10,000 years accelerated the rate of evolution because “we were in new environments to which we needed to adapt,” Harpending adds. “And with a larger population, more mutations occurred.”

Study co-author Gregory M. Cochran says: “History looks more and more like a science fiction novel in which mutants repeatedly arose and displaced normal humans — sometimes quietly, by surviving starvation and disease better, sometimes as a conquering horde. And we are those mutants.”

Harpending conducted the study with Cochran, a New Mexico physicist, self-taught evolutionary biologist and adjunct professor of anthropology at the University of Utah; anthropologist John Hawks, a former Utah postdoctoral researcher now at the University of Wisconsin, Madison; geneticist Eric Wang of Affymetrix, Inc. in Santa Clara, Calif.; and biochemist Robert Moyzis of the University of California, Irvine.

No Justification for Discrimination

The new study comes from two of the same University of Utah scientists — Harpending and Cochran — who created a stir in 2005 when they published a study arguing that above-average intelligence in Ashkenazi Jews — those of northern European heritage — resulted from natural selection in medieval Europe, where they were pressured into jobs as financiers, traders, managers and tax collectors. Those who were smarter succeeded, grew wealthy and had bigger families to pass on their genes. Yet that intelligence also is linked to genetic diseases such as Tay-Sachs and Gaucher in Jews.

That study and others dealing with genetic differences among humans — whose DNA is more than 99 percent identical — generated fears such research will undermine the principle of human equality and justify racism and discrimination. Other critics question the quality of the science and argue culture plays a bigger role than genetics.

Harpending says genetic differences among different human populations “cannot be used to justify discrimination. Rights in the Constitution aren’t predicated on utter equality. People have rights and should have opportunities whatever their group.”

Analyzing SNPs of Evolutionary Acceleration

The study looked for genetic evidence of natural selection — the evolution of favorable gene mutations — during the past 80,000 years by analyzing DNA from 270 individuals in the International HapMap Project, an effort to identify variations in human genes that cause disease and can serve as targets for new medicines.

The new study looked specifically at genetic variations called “single nucleotide polymorphisms,” or SNPs (pronounced “snips”) which are single-point mutations in chromosomes that are spreading through a significant proportion of the population.

Imagine walking along two chromosomes — the same chromosome from two different people. Chromosomes are made of DNA, a twisting, ladder-like structure in which each rung is made of a “base pair” of amino acids, either G-C or A-T. Harpending says that about every 1,000 base pairs, there will be a difference between the two chromosomes. That is known as a SNP.

Data examined in the study included 3.9 million SNPs from the 270 people in four populations: Han Chinese, Japanese, Africa’s Yoruba tribe and northern Europeans, represented largely by data from Utah Mormons, says Harpending.

Over time, chromosomes randomly break and recombine to create new versions or variants of the chromosome. “If a favorable mutation appears, then the number of copies of that chromosome will increase rapidly” in the population because people with the mutation are more likely to survive and reproduce, Harpending says.

“And if it increases rapidly, it becomes common in the population in a short time,” he adds.

The researchers took advantage of that to determine if genes on chromosomes had evolved recently. Humans have 23 pairs of chromosomes, with each parent providing one copy of each of the 23. If the same chromosome from numerous people has a segment with an identical pattern of SNPs, that indicates that segment of the chromosome has not broken up and recombined recently.

That means a gene on that segment of chromosome must have evolved recently and fast; if it had evolved long ago, the chromosome would have broken and recombined.

Harpending and colleagues used a computer to scan the data for chromosome segments that had identical SNP patterns and thus had not broken and recombined, meaning they evolved recently. They also calculated how recently the genes evolved.

A key finding: 7 percent of human genes are undergoing rapid, recent evolution.

The researchers built a case that human evolution has accelerated by comparing genetic data with what the data should look like if human evolution had been constant:

• The study found much more genetic diversity in the SNPs than would be expected if human evolution had remained constant.
• If the rate at which new genes evolve in Africans was extrapolated back to 6 million years ago when humans and chimpanzees diverged, the genetic difference between modern chimps and humans would be 160 times greater than it really is. So the evolution rate of Africans represents a recent speedup in evolution.
• If evolution had been fast and constant for a long time, there should be many recently evolved genes that have spread to everyone. Yet, the study revealed many genes still becoming more frequent in the population, indicating a recent evolutionary speedup.

Next, the researchers examined the history of human population size on each continent. They found that mutation patterns seen in the genome data were consistent with the hypothesis that evolution is faster in larger populations.

Evolutionary Change and Human History: Got Milk?

“Rapid population growth has been coupled with vast changes in cultures and ecology, creating new opportunities for adaptation,” the study says. “The past 10,000 years have seen rapid skeletal and dental evolution in human populations, as well as the appearance of many new genetic responses to diet and disease.”

The researchers note that human migrations into new Eurasian environments created selective pressures favoring less skin pigmentation (so more sunlight could be absorbed by skin to make vitamin D), adaptation to cold weather and dietary changes.

Because human population grew from several million at the end of the Ice Age to 6 billion now, more favored new genes have emerged and evolution has speeded up, both globally and among continental groups of people, Harpending says.

“We have to understand genetic change in order to understand history,” he adds.

For example, in China and most of Africa, few people can digest fresh milk into adulthood. Yet in Sweden and Denmark, the gene that makes the milk-digesting enzyme lactase remains active, so “almost everyone can drink fresh milk,” explaining why dairying is more common in Europe than in the Mediterranean and Africa, Harpending says.

He now is studying if the mutation that allowed lactose tolerance spurred some of history’s great population expansions, including when speakers of Indo-European languages settled all the way from northwest India and central Asia through Persia and across Europe 4,000 to 5,000 years ago. He suspects milk drinking gave lactose-tolerant Indo-European speakers more energy, allowing them to conquer a large area.

But Harpending believes the speedup in human evolution “is a temporary state of affairs because of our new environments since the dispersal of modern humans 40,000 years ago and especially since the invention of agriculture 12,000 years ago. That changed our diet and changed our social systems. If you suddenly take hunter-gatherers and give them a diet of corn, they frequently get diabetes. We’re still adapting to that. Several new genes we see spreading through the population are involved with helping us prosper with high-carbohydrate diet.”

PNAS | January 8, 2002 | vol. 99 | no. 1 | 10-12

Commentary
In our genes

Henry Harpending^*, and Gregory Cochran Department of Anthropology, University of Utah, Salt Lake City, UT 84112; and Reconstruction Concepts, 6708 Loftus Northeast, Albuquerque, NM 87109

The D4 dopamine receptor (DRD4) locus may be a model system for understanding the relationship between genetic variation and human cultural diversity. It has been the subject of intense interest in psychiatry, because bearers of one variant are at increased risk for attention deficit hyperactivity disorder (ADHD) (1). A survey of world frequencies of DRD4 alleles has shown striking differences among populations (2), with population differences greater than those of most neutral markers. In this issue of PNAS Ding et al. (3) provide a detailed molecular portrait of world diversity at the DRD4 locus. They show that the allele associated with ADHD has increased a lot in frequency within the last few thousands to tens of thousands of years, although it has probably been present in our ancestors for hundreds of thousands or even millions of years. There is a repeat polymorphism in exon III of the gene at which a variable number of 48-bp motifs can occur. The common and probable ancestral allele has four repeats (4R), whereas the allele associated with novelty seeking and ADHD has seven (7R). Ding et al. (3) show that there are essentially two allele classes at the locus: most variants are easily derived from 4R by simple recombinations or mutations, whereas 7R differs from 4R by a minimum of seven events. This means either that the coalescence of the 4R and 7R allele classes is ancient or that 7R was generated by an extremely improbable mutation and recombination event more recently. At any rate the allelic diversity within the 4R class and the lack of linkage disequilibrium with markers around it show that it has been the common variant in our species for a long time. 7R alleles, with little diversity within the class and . . . [Full Text of this Article]

see also:

Evidence of positive selection acting at the human dopamine receptor D4 gene locus

Yuan-Chun Ding, Han-Chang Chi, Deborah L. Grady, Atsuyuki Morishima, Judith R. Kidd, Kenneth K. Kidd, Pamela Flodman, M. Anne Spence, Sabrina Schuck, James M. Swanson, Ya-Ping Zhang, and Robert K. Moyzis
PNAS 2002 99: 309-314. [Abstract] [Full Text]

Observations about the early formation of Earth may answer an age-old question about why the planet’s mantle is missing some of the matter that should be present, according to UBC geophysicist John Hernlund.

Earth is made from chondrite, very primitive rocks of meteorites that date from the earliest time of the solar system before the Earth was formed. However, scientists have been puzzled why the composition of Earth’s mantle and core differed from that of chondrite.

Hernlund’s findings suggest that an ancient magma ocean swirled beneath the Earth’s surface and would account for the discrepancy.

Over its 4.5 billion history, Earth’s layers of molten rock evolved and crystallized, cooling from a magma ocean (yellow) to the mantle (grey) around the planet’s core (orange). (Credit: Image courtesy of University of British Columbia)

“As the thick melted rock cooled and crystallized, the solids that resulted had a different composition than the melt,” explains Hernlund, a post-doctoral fellow at UBC Earth and Ocean Sciences.

“The melt held onto some of the elements. This would be where the missing elements of chondrite are stored.”

He says this layer of molten rock would have been around 1,000 km thick and 2,900 km beneath the surface.”

Hernlund’s study explores the melting and crystallization processes that have controlled the composition of the Earth’s interior over geological time. Co-authors are Stéphane Labrosse, Ecole Normale Superieure de Lyon and Nicolas Coltice, Université de Lyon.

The centre of Earth is a fiery core of melted heavy metals, mostly iron. This represents 30 per cent while the remaining 70 per cent is the outer mantle of solid rock.

Traditional views hold that a shallow ocean of melted rock (magma) existed 1,000 km below the Earth’s surface, but it was short lived and gone by 10 million years after the formation of Earth.

In contrast, Hernlund’s evolutionary model predicts that during Earth’s hotter past shortly after its formation 4.5 billion years ago, at least one-third of the mantle closest to the core was also melted.

The partially molten patches now observed at the base of the Earth’s mantle could be the remnants of such a deep magma ocean, says Hernlund.

Letter

Nature 450, 866-869 (6 December 2007) | doi:10.1038/nature06355; Received 21 May 2007; Accepted 2 October 2007

A crystallizing dense magma ocean at the base of the Earth’s mantle

S. Labrosse1, J. W. Hernlund2,4 & N. Coltice1,3

1. Laboratoire des sciences de la Terre, Ecole Normale Supérieure de Lyon, Université de Lyon, CNRS UMR 5570, 46 Allée d’Italie, 69364 Lyon Cedex 07, France
2. Équipe de Dynamique des Fluides Géologiques, Institut de Physique du Globe de Paris, 4 place Jussieu, 75252 Paris Cedex 05, France
3. Laboratoire des sciences de la Terres, Université Lyon 1, Université de Lyon, CNRS UMR 5570, 2 rue Raphael Dubois, 69622 Villeurbanne Cedex, France
4. Present address: Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.

Correspondence to: S. Labrosse1 Correspondence and requests for materials should be addressed to S.L. (Email: stephane.labrosse@ens-lyon.fr).

The distribution of geochemical species in the Earth’s interior is largely controlled by fractional melting and crystallization processes that are intimately linked to the thermal state and evolution of the mantle. The existence of patches of dense partial melt at the base of the Earth’s mantle, together with estimates of melting temperatures for deep mantle phases and the amount of cooling of the underlying core required to maintain a geodynamo throughout much of the Earth’s history, suggest that more extensive deep melting occurred in the past. Here we show that a stable layer of dense melt formed at the base of the mantle early in the Earth’s history would have undergone slow fractional crystallization, and would be an ideal candidate for an unsampled geochemical reservoir hosting a variety of incompatible species (most notably the missing budget of heat-producing elements) for an initial basal magma ocean thickness of about 1,000 km. Differences in 142Nd/144Nd ratios between chondrites and terrestrial rocks can be explained by fractional crystallization with a decay timescale of the order of 1 Gyr. These combined constraints yield thermal evolution models in which radiogenic heat production and latent heat exchange prevent early cooling of the core and possibly delay the onset of the geodynamo to 3.4–4 Gyr ago.

Evidence Suggests Vitamin D Deficiency Endangers Migrating Populations

Although most scientists believe tuberculosis emerged only several thousand years ago, new research from The University of Texas at Austin reveals the most ancient evidence of the disease has been found in a 500,000-year-old human fossil from Turkey.

The discovery of the new specimen of the human species, Homo erectus, suggests support for the theory that dark-skinned people who migrate northward from low, tropical latitudes produce less vitamin D, which can adversely affect the immune system as well as the skeleton.

Prior to this discovery in western Turkey, which helps scientists fill a temporal and geographical gap  in human evolution, the oldest evidence of tuberculosis in humans was found in mummies from Egypt and Peru that date to several thousand years ago.

Paleontologists spent decades prospecting in Turkey for remains of Homo erectus, widely believed to be the first human species to migrate out of Africa. After moving north, the species had to adapt to increasingly seasonal climates.

The researchers identified this specimen of Homo erectus as a young male based on aspects of the cranial suture closure, sinus formation and the size of the ridges of the brow. They also found a series of small lesions etched into the bone of the cranium whose shape and location are characteristic of the Leptomeningitis tuberculosa, a form of tuberculosis that attacks the meninges of the brain.

After reviewing the medical literature on the disease that has reemerged as a global killer, the researchers found that some groups of people demonstrate a higher than average rate of infection, including Gujarati Indians who live in London, and Senegalese conscripts who served with the French army during World War I.

The research team identified two shared characteristics in the communities: a path of migration from low, tropical latitudes to northern temperate regions and darker skin color.

People with dark skin produce less vitamin D because the skin pigment melanin blocks ultraviolet light. And, when they live in areas with lower ultraviolet radiation such as Europe, their immune systems can be compromised.

John Kappelman, professor of anthropology at The University of Texas at Austin, is part of an international team of researchers from the United States, Turkey and Germany who have published their findings in the Dec. 7 issue of the American Journal of Physical Anthropology.

It is likely that Homo erectus had dark skin because it evolved in the tropics, Kappelman explained. After the species moved north, it had to adapt to more seasonal climates. The researchers hypothesize the young male’s body produced less vitamin D and this deficiency weakened his immune system, opening the door to tuberculosis.

“Skin color represents one of biology’s most elegant adaptations,” Kappelman said. “The production of vitamin D in the skin serves as one of the body’s first lines of defenses against a whole host of infections and diseases. Vitamin D deficiencies are implicated in hypertension, multiple sclerosis, cardiovascular disease and cancer.”

Before antibiotics were invented, doctors typically treated tuberculosis by sending patients to sanatoria where they were prescribed plenty of sunshine and fresh air.

“No one knew why sunshine was integral to the treatment, but it worked,” Kappelman said. “Recent research suggests the flush of ultraviolet radiation jump-started the patients’ immune systems by increasing the production of vitamin D, which helped to cure the disease.”

View of the inside of a plaster cast of the skull of the newly discovered young male Homo erectus from western Turkey. The stylus points to tiny lesions 1-2 mm in size found along the rim of bone just behind the right eye orbit. The lesions were formed by a type of tuberculosis that infects the brain and, at 500,000 years in age, represents the most ancient case

American Journal of Physical Anthropology 7 Dec 2007 Early View DOI 10.1002/ajpa.20739
Brief Communication
First Homo erectus from Turkey and implications for migrations into temperate Eurasia
John Kappelman 1 *, Mehmet Cihat Alçiçek 2, Nizamettin Kazanc 3 4, Michael Schultz 5, Mehmet Özkul 2 4, evket en 6
1Department of Anthropology, The University of Texas, Austin, TX
2Department of Geological Engineering, Engineering Faculty, Pamukkale University, Denizli, Turkey
3Department of Geological Engineering, Engineering Faculty, Ankara University, Ankara, Turkey
4JEMIRKO, Turkish Association for Protection of Geological Heritage, Ankara, Turkey
5Zentrum Anatomie der Georg-August-Universität, Göttingen, Germany D-37075
6Laboratoire de Paléontologie du Muséum National d’Histoire Naturelle, Paris, France
email: John Kappelman (jkappelman@mail.utexas.edu)

*Correspondence to John Kappelman, The University of Texas at Austin, Anthrop and Archeol, 1 University Station C3200, Austin, TX 78712-0303, USA

Abstract
Remains of fossil hominins from temperate regions of the Old World are rare across both time and space, but such specimens are necessary for understanding basic issues in human evolution including linkages between their adaptations and early migration patterns. We report here the remarkable circumstances surrounding the discovery of the first fossil hominin calvaria from Turkey. The specimen was found in the Denizli province of western Turkey and recovered from within a solid block of travertine stone as it was being sawed into tile-sized slabs for the commercial natural stone building market. The new specimen fills an important geographical and temporal gap and displays several anatomical features that are shared with other Middle Pleistocene hominins from both Africa and Asia attributed to Homo erectus. It also preserves an unusual pathology on the endocranial surface of the frontal bone that is consistent with a diagnosis of Leptomeningitis tuberculosa (TB), and this evidence represents the most ancient example of this disease known for a fossil human. TB is exacerbated in dark-skinned peoples living in northern latitudes by a vitamin D deficiency because of reduced levels of ultraviolet radiation (UVR). Evidence for TB in the new specimen supports the thesis that reduced UVR was one of the many climatic variables presenting an adaptive challenge to ancient hominins during their migration into the temperate regions of Europe and Asia. Am J Phys Anthropol, 2007. © 2007 Wiley-Liss, Inc.

see also:

American Journal of Physical Anthropology Volume 134, Issue S45 , Pages 85 - 105

Research Article

Human pigmentation variation: Evolution, genetic basis, and implications for public health

Esteban J. Parra
Department of Anthropology, University of Toronto at Mississauga, Mississauga, ON, Canada L5L 1C6

email: Esteban J. Parra (esteban.parra@utoronto.ca) Correspondence to Esteban J. Parra, Department of Anthropology, University of Toronto at Mississauga, 3559 Mississauga Road North, Room 212 North Building, Mississauga, ON, Canada L5L 1C6

Pigmentation, which is primarily determined by the amount, the type, and the distribution of melanin, shows a remarkable diversity in human populations, and in this sense, it is an atypical trait. Numerous genetic studies have indicated that the average proportion of genetic variation due to differences among major continental groups is just 10-15% of the total genetic variation. In contrast, skin pigmentation shows large differences among continental populations. The reasons for this discrepancy can be traced back primarily to the strong influence of natural selection, which has shaped the distribution of pigmentation according to a latitudinal gradient. Research during the last 5 years has substantially increased our understanding of the genes involved in normal pigmentation variation in human populations. At least six genes have been identified using genotype/phenotype association studies and/or direct functional assays, and there is evidence indicating that several additional genes may be playing a role in skin, hair, and iris pigmentation. The information that is emerging from recent studies points to a complex picture where positive selection has been acting at different genomic locations, and for some genes only in certain population groups. There are several reasons why elucidating the genetics and evolutionary history of pigmentation is important. 1) Pigmentation is a trait that should be used as an example of how misleading simplistic interpretations of human variation can be. It is erroneous to extrapolate the patterns of variation observed in superficial traits such as pigmentation to the rest of the genome. It is similarly misleading to suggest, based on the average genomic picture, that variation among human populations is irrelevant. The study of the genes underlying human pigmentation diversity brings to the forefront the mosaic nature of human genetic variation: our genome is composed of a myriad of segments with different patterns of variation and evolutionary histories. 2) Pigmentation can be very useful to understand the genetic architecture of complex traits. The pigmentation of unexposed areas of the skin (constitutive pigmentation) is relatively unaffected by environmental influences during an individual’s lifetime when compared with other complex traits such as diabetes or blood pressure, and this provides a unique opportunity to study gene-gene interactions without the effect of environmental confounders. 3) Pigmentation is of relevance from a public health perspective, because of its critical role in photoprotection and vitamin D synthesis. Fair-skinned individuals are at higher risk of several types of skin cancer, particularly in regions with high UVR incidence, and dark-skinned individuals living in high latitude regions are at higher risk for diseases caused by deficient or insufficient vitamin D levels. Yrbk Phys Anthropol 50:85-105, 2007. © 2007 Wiley-Liss, Inc.

 What GWB’s manners do suggest, seems highly likely in the light of genetic research: Americans are Siberians by provenance. Native Americans should not feel offended by this, we all know, that the Bush Clan is not native to the Americas. Seriously now, did a relatively small number of people from Siberia who trekked across a Bering Strait land bridge some 12,000 years ago give rise to the native peoples of North and South America?

The U-M study, which analyzed genetic data from 29 Native American populations, suggests a Siberian origin is much more likely than a South Asian or Polynesian origin. (Credit: University of Michigan)

Or did the ancestors of today’s native peoples come from other parts of Asia or Polynesia, arriving multiple times at several places on the two continents, by sea as well as by land, in successive migrations that began as early as 30,000 years ago?

The questions — featured on magazine covers and TV specials — have agitated anthropologists, archaeologists and others for decades.

University of Michigan scientists, working with an international team of geneticists and anthropologists, have produced new genetic evidence that’s likely to hearten proponents of the land bridge theory. The study, published online in PLoS Genetics, is one of the most comprehensive analyses so far among efforts to use genetic data to shed light on the topic.

The researchers examined genetic variation at 678 key locations or markers in the DNA of present-day members of 29 Native American populations across North, Central and South America. They also analyzed data from two Siberian groups. The analysis shows:

o genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait — adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.

o a unique genetic variant is widespread in Native Americans across both American continents — suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources. The variant, which is not part of a gene and has no biological function, has not been found in genetic studies of people elsewhere in the world except eastern Siberia.

The researchers say the variant likely occurred shortly prior to migration to the Americas, or immediately afterwards.

“We have reasonably clear genetic evidence that the most likely candidate for the source of Native American populations is somewhere in east Asia,” says Noah A. Rosenberg, Ph.D., assistant professor of human genetics and assistant research professor of bioinformatics at the Center for Computational Medicine and Biology at the U-M Medical School and assistant research professor at the U-M Life Sciences Institute.

“If there were a large number of migrations, and most of the source groups didn’t have the variant, then we would not see the widespread presence of the mutation in the Americas,” he says.

Rosenberg has previously studied the same set of 678 genetic markers used in the new study in 50 populations around the world, to learn which populations are genetically similar and what migration patterns might explain the similarities. For North and South America, the current research breaks new ground by looking at a large number of native populations using a large number of markers.

The pattern the research uncovered — that as the founding populations moved south from the Bering Strait, genetic diversity declined — is what one would expect when migration is relatively recent, says Mattias Jakobsson, Ph.D., co-first author of the paper and a post-doctoral fellow in human genetics at the U-M Medical School and the U-M Center for Computational Medicine and Biology. There has not been time yet for mutations that typically occur over longer periods to diversify the gene pool.

In addition, the study’s findings hint at supporting evidence for scholars who believe early inhabitants followed the coasts to spread south into South America, rather than moving in waves across the interior.

“Assuming a migration route along the coast provides a slightly better fit with the pattern we see in genetic diversity,” Rosenberg says.

The study also found that:

• Populations in the Andes and Central America showed genetic similarities.
• Populations from western South America showed more genetic variation than populations from eastern South America.
• Among closely related populations, the ones more similar linguistically were also more similar genetically.

PLoS Genet 3(11): e185 doi:10.1371/journal.pgen.0030185

Genetic Variation and Population Structure in Native Americans. 

Wang S, Lewis Jr. CM, Jakobsson M, Ramachandran S, Ray N, et al. (2007) 

 We examined genetic diversity and population structure in the American landmass using 678 autosomal microsatellite markers genotyped in 422 individuals representing 24 Native American populations sampled from North, Central, and South America. These data were analyzed jointly with similar data available in 54 other indigenous populations worldwide, including an additional five Native American groups. The Native American populations have lower genetic diversity and greater differentiation than populations from other continental regions. We observe gradients both of decreasing genetic diversity as a function of geographic distance from the Bering Strait and of decreasing genetic similarity to Siberians—signals of the southward dispersal of human populations from the northwestern tip of the Americas. We also observe evidence of: (1) a higher level of diversity and lower level of population structure in western South America compared to eastern South America, (2) a relative lack of differentiation between Mesoamerican and Andean populations, (3) a scenario in which coastal routes were easier for migrating peoples to traverse in comparison with inland routes, and (4) a partial agreement on a local scale between genetic similarity and the linguistic classification of populations. These findings offer new insights into the process of population dispersal and differentiation during the peopling of the Americas.

Author Summary

Studies of genetic variation have the potential to provide information about the initial peopling of the Americas and the more recent history of Native American populations. To investigate genetic diversity and population relationships in the Americas, we analyzed genetic variation at 678 genome-wide markers genotyped in 29 Native American populations. Comparing Native Americans to Siberian populations, both genetic diversity and similarity to Siberians decrease with geographic distance from the Bering Strait. The widespread distribution of a particular allele private to the Americas supports a view that much of Native American genetic ancestry may derive from a single wave of migration. The pattern of genetic diversity across populations suggests that coastal routes might have been important during ancient migrations of Native American populations. These and other observations from our study will be useful alongside archaeological, geological, and linguistic data for piecing together a more detailed description of the settlement history of the Americas.

Is there an objective biological basis for the experience of beauty in art? Or is aesthetic experience entirely subjective? This question has been addressed in a new article by Cinzia Di Dio, Emiliano Macaluso and Giacomo Rizzolatti. The researchers used fMRI scans to study the neural activity in subjects with no knowledge of art criticism, who were shown images of Classical and Renaissance sculptures.

Brain activations in the contrasts “judged-as-beautiful vs. judged-as-ugly” and “judged-as-ugly vs. judged-as-beautiful” stimuli. Statistical parametric maps rendered onto the MNI brain template showing activity within left somatomotor cortex in the contrast of ugly vs. beautiful stimuli averaged across the three conditions. (Credit: Di Dio C, Macaluso E, Rizzolatti G,Image courtesy of PLoS One)

The ‘objective’ perspective was examined by contrasting images of Classical and Renaissance sculptures of canonical proportions, with images of the same sculptures whose proportions were altered to create a comparable degraded aesthetic value. In terms of brain activations, this comparison showed that the presence of the “golden ratio” in the original material activated specific sets of cortical neurons as well as (crucially) the insula, a structure mediating emotions. This response was particularly apparent when participants were only required to observe the stimuli; that is, when the brain reacted most spontaneously to the images presented.

The ’subjective’ perspective was evaluated by contrasting beautiful vs. ugly sculptures, this time as judged by each participant who decided whether or not the sculpture was aesthetic. The images judged to be beautiful selectively activated the right amygdala, a structure that responds tolearned incoming information laden with emotional value.

These results indicate that, in observers naïve to art criticism, the sense of beauty is mediated by two non-mutually exclusive processes: one is based on a joint activation of sets of cortical neurons, triggered by parameters intrinsic to the stimuli, and the insula (objective beauty); the other is based on the activation of the amygdala, driven by one’s own emotional experiences (subjective beauty). The researchers conclude that both objective and subjective factors intervene in determining our appreciation of an artwork.

The history of art is replete with the constant tension between objective values and subjective judgments. This tension is deepened when artists discover new aesthetic parameters that may appeal for various reasons, be they related to our biological heritage, or simply to fashion or novelty. Still, the central question remains: when the fashion and novelty expire, could their work ever become a permanent patrimony of humankind without a resonance induced by some biologically inherent parameters?

PLoS ONE 2(11): e1201. doi:10.1371/journal.pone.0001201

The Golden Beauty: Brain Response to Classical and Renaissance Sculptures.

Di Dio C, Macaluso E, Rizzolatti G (2007)

Abstract

Is there an objective, biological basis for the experience of beauty in art? Or is aesthetic experience entirely subjective? Using fMRI technique, we addressed this question by presenting viewers, naïve to art criticism, with images of masterpieces of Classical and Renaissance sculpture. Employing proportion as the independent variable, we produced two sets of stimuli: one composed of images of original sculptures; the other of a modified version of the same images. The stimuli were presented in three conditions: observation, aesthetic judgment, and proportion judgment. In the observation condition, the viewers were required to observe the images with the same mind-set as if they were in a museum. In the other two conditions they were required to give an aesthetic or proportion judgment on the same images. Two types of analyses were carried out: one which contrasted brain response to the canonical and the modified sculptures, and one which contrasted beautiful vs. ugly sculptures as judged by each volunteer. The most striking result was that the observation of original sculptures, relative to the modified ones, produced activation of the right insula as well as of some lateral and medial cortical areas (lateral occipital gyrus, precuneus and prefrontal areas). The activation of the insula was particularly strong during the observation condition. Most interestingly, when volunteers were required to give an overt aesthetic judgment, the images judged as beautiful selectively activated the right amygdala, relative to those judged as ugly. We conclude that, in observers naïve to art criticism, the sense of beauty is mediated by two non-mutually exclusive processes: one based on a joint activation of sets of cortical neurons, triggered by parameters intrinsic to the stimuli, and the insula (objective beauty); the other based on the activation of the amygdala, driven by one’s own emotional experiences (subjective beauty).

Tiny DNA Molecules Show Liquid Crystal Phases, Pointing Up New Scenario For First Life On Earth

A team led by the University of Colorado at Boulder and the University of Milan has discovered some unexpected forms of liquid crystals of ultrashort DNA molecules immersed in water, providing a new scenario for a key step in the emergence of life on Earth

A colorful microscope image showing that a solution of tiny DNA molecules has formed a liquid-crystal phase. The DNA molecules pair to form DNA double helices, which, in turn stack end-to-end to make rod-shaped aggregates that orient parallel to one another. (Credit: Michi Nakata)

CU-Boulder physics Professor Noel Clark said the team found that surprisingly short segments of DNA, life’s molecular carrier of genetic information, could assemble into several distinct liquid crystal phases that “self-orient” parallel to one another and stack into columns when placed in a water solution. Life is widely believed to have emerged as segments of DNA- or RNA-like molecules in a prebiotic “soup” solution of ancient organic molecules.

Since the formation of molecular chains as uniform as DNA by random chemistry is essentially impossible, Clark said, scientists have been seeking effective ways for simple molecules to spontaneously self-select, “chain-up” and self-replicate. The new study shows that in a mixture of tiny fragments of DNA, those molecules capable of forming liquid crystals selectively condense into droplets in which conditions are favorable for them to be chemically linked into longer molecules with enhanced liquid crystal-forming tendencies, he said.

“We found that even tiny fragments of double helix DNA can spontaneously self-assemble into columns that contain many molecules,” Clark said. “Our vision is that from the collection of ancient molecules, short RNA pieces or some structurally related precursor emerged as the molecular fragments most capable of condensing into liquid crystal droplets, selectively developing into long molecules.”

Liquid crystals — organic materials related to soap that exhibit both solid and liquid properties — are commonly used for information displays in computers, flat-panel televisions, cell phones, calculators and watches. Most liquid crystal phase molecules are rod-shaped and have the ability to spontaneously form large domains of a common orientation, which makes them particularly sensitive to stimuli like changes in temperature or applied voltage.

RNA and DNA are chain-like polymers with side groups known as nucleotides, or bases, that selectively adhere only to specific bases on a second chain. Matching, or complementary base sequences enable the chains to pair up and form the widely recognized double helix structure. Genetic information is encoded in sequences of thousands to millions of bases along the chains, which can be microns to millimeters in length.

Such DNA polynucleotides had previously been shown to organize into liquid crystal phases in which the chains spontaneously oriented parallel to each other, he said. Researchers understand the liquid crystal organization to be a result of DNA’s elongated molecular shape, making parallel alignment easier, much like spaghetti thrown in a box and shaken would be prone to line up in parallel, Clark said.

A paper on the subject was published in the Nov. 23 issue of Science. The paper was authored by Clark, Michi Nakata and Christopher Jones from CU-Boulder, Giuliano Zanchetta and Tommaso Bellini of the University of Milan, Brandon Chapman and Ronald Pindak of Brookhaven National Laboratory and Julie Cross of Argonne National Laboratory. Nakata died in September 2006.

The CU-Boulder and University of Milan team began a series of experiments to see how short the DNA segments could be and still show liquid crystal ordering, said Clark. The team found that even a DNA segment as short as six bases, when paired with a complementary segment that together measured just two nanometers long and two nanometers in diameter, could still assemble itself into the liquid crystal phases, in spite of having almost no elongation in shape.

Structural analysis of the liquid crystal phases showed that they appeared because such short DNA duplex pairs were able to stick together “end-to-end,” forming rod-shaped aggregates that could then behave like much longer segments of DNA. The sticking was a result of small, oily patches found on the ends of the short DNA segments that help them adhere to each other in a reversible way — much like magnetic buttons — as they expelled water in between them, Clark said.

A key characterization technique employed was X-ray microbeam diffraction combined with in-situ optical microscopy, carried out with researchers from Argonne and Brookhaven National Laboratories. The team using a machine called the Argonne Advanced Photon Source synchrotron that enabled probing of the “nano DNA” molecular organization in single liquid crystal orientation domains only a few microns in size. The experiments provided direct evidence for the columnar stacking of the nano DNA pieces in a fluid liquid crystal phase.

“The key observation with respect to early life is that this aggregation of nano DNA strands is possible only if they form duplexes,” Clark said. “In a sample of chains in which the bases don’t match and the chains can’t form helical duplexes, we did not observe liquid crystal ordering.”

Subsequent tests by the team involved mixed solutions of complementary and noncomplementary DNA segments, said Clark. The results indicated that essentially all of the complementary DNA bits condensed out in the form of liquid crystal droplets, physically separating them from the noncomplementary DNA segments.

“We found this to be a remarkable result,” Clark said. “It means that small molecules with the ability to pair up the right way can seek each other out and collect together into drops that are internally self-organized to facilitate the growth of larger pairable molecules.

“In essence, the liquid crystal phase condensation selects the appropriate molecular components, and with the right chemistry would evolve larger molecules tuned to stabilize the liquid crystal phase. If this is correct, the linear polymer shape of DNA itself is a vestige of formation by liquid crystal order.”
Science 23 November 2007:Vol. 318. no. 5854, pp. 1276 - 1279 DOI: 10.1126/science.1143826

End-to-End Stacking and Liquid Crystal Condensation of 6– to 20–Base Pair DNA Duplexes
Michi Nakata,^1* Giuliano Zanchetta,^2* Brandon D. Chapman,³ Christopher D. Jones,¹ Julie O. Cross,⁴ Ronald Pindak,³ Tommaso Bellini,² Noel A. Clark¹

Short complementary B-form DNA oligomers, 6 to 20 base pairs in length, are found to exhibit nematic and columnar liquid crystal phases, even though such duplexes lack the shape anisotropy required for liquid crystal ordering. Structural study shows that these phases are produced by the end-to-end adhesion and consequent stacking of the duplex oligomers into polydisperse anisotropic rod-shaped aggregates, which can order into liquid crystals. Upon cooling mixed solutions of short DNA oligomers, in which only a small fraction of the DNA present is complementary, the duplex-forming oligomers phase-separate into liquid crystal droplets, leaving the unpaired single strands in isotropic solution. In a chemical environment where oligomer ligation is possible, such ordering and condensation would provide an autocatalytic link whereby complementarity promotes the extended polymerization of complementary oligomers.

¹ Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309–0390, USA.
² Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Università di Milano, Milano, Italy.
³ National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA.
⁴ Advanced Photon Source, Argonne National Laboratory, Argonne, IL60439, USA.

^* These authors contributed equally to this work.

Deceased.

To whom correspondence should be addressed. E-mail: tommaso.bellini@unimi.it

see also:

MULTIPLE LIQUID CRYSTAL PHASES
OF DNA AT HIGH CONCENTRATIONS

Teresa E. Strzelecka
Michael W. Davidson & Randolph L. Rill
Department of Chemistry
and Institute of Molecular Biophysics
The Florida State University
Tallahassee, Florida 32306-3006, USA

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids^1-3. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions^4-8. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, `precholesteric’ mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to 10 µm. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.

Although specialized proteins are involved in many DNA packaging processes descriptions of mechanisms of DNA packaging must also consider the intrinsic tendency of the stiff DNA chain to fold when confined to a small volume. Stiff nonelectrolyte polymers form highly ordered, liquid crystalline phases above a critical concentration dependent on the persistence length^4-8. Formation of nematic or cholesteric liquid crystalline phases by semi-rigid polymers, such as polybenzyl-L-glutamate, in organic solvents has been studied in detail^7,8, and was predicted theoretically by Onsager⁴, Flory^5,6 and others. Much less is known about the behavior of semi-rigid polyelectrolytes. Because DNA, fibrous proteins and certain polysaccharides are polyelectrolytes involved in numerous supramolecular associations in vivo, an understanding of the phase behavior of these biopolymers is of fundamental biological importance.

Ordering of semi-rigid polymers at high concentrations occurs spontaneously to minimize the macromolecular excluded volume^4-8. Semi-rigid polyelectrolyte behavior is complicated by charge-shielding requirements. A strong polyelectrolyte is surrounded by a counterion layer, which determines the effective axial ratio and excluded volume^9-13. Because polymer phase behavior depends on the effective polymer dimensions, the critical concentration for DNA ordering is a sensitive function if ionic strength and counterion type.

Previous studies demonstrated that aqueous solutions of persistence length DNA (~500 Å), with 0.3 M NaCl as the supporting electrolyte, form biphasic liquid crystalline solutions containing spherulites at DNA concentrations (C_Ds) of 130-170 mg DNA ml^-1 at room temperature, and become fully liquid crystalline at higher C_D (refs 14-16). Phase transition boundaries were in good agreement with predicted rigid rod behavior when DNA was treated as a scaled rod with an effective radius of 21.5 Å at this ionic strength¹⁶. Here we report the phase behavior when DNA solutions over a range of C_Ds from 100 to 350 mg DNA ml^-1, as determined by solid-state ³¹P NMR spectroscopy, polarized light microscopy and by electron microscopy.Solutions showed a uniform liquid crystalline phase at C_Ds from 170 to 220 mg ml^-1. A C_D of 170-mg ml^-1 corresponds to an effective DNA volume fraction of 0.76, assuming 21.5 Å for the effective DNA radius¹⁶. Extrapolation to higher C_Ds yields an apparent effective volume fraction > 1.0 for C_Ds exceeding ~230 mg ml^-1. As DNA solutions were prepared with C_Ds over 300-mg ml^-1, there must be mechanisms for reducing the effective DNA volume fraction.Three potential mechanisms for reducing the effective DNA volume are evident: (1) a change to a more ordered phase, (2) a contraction of the counterion layer, or (3) a change in DNA confirmation/hydration. A phase change above C_Ds of 220-mg ml^-1 was indicated by a change in ³¹P resonance linewidth and shape(Fig. 1). At lower C_Ds, in the biphasic region, the resonance linewidth increased progressively with C_D until the solution became fully liquid-crystalline, then dramatically sharpened. Concurrently, the lineshape changed from lorenzian to an asymmetric form excepted from an aligned sample with some rotational averaging. Magnetic alignment of liquid crystalline DNA phases with the long molecular axes perpendicular to the field was reported eviously^16,17.

Figure 2(a&b)

Figure 2(c&d)

Figure 2(e&f)

Magnetic alignment of the mesophase in a biphasic solution is prevented because surface tension restricts the mesophase to spherulites in which DNA molecules are oriented tangentially to the spherical surface¹⁸. By analogy, we attribute lineshape changes at C_Ds slightly above 220-mg ml^-1 to formation of a biphasic solution in which two liquid-crystalline phases coexist. Magnetic alignment may be ineffective because of dynamic exchange of molecules between phases with different alignment properties. This conclusion was enforced by the behavior at yet higher C_Ds (Fig 1). The resonance remained broad at C_Ds from 229 to 240 mg ml^-1, then narrowed again at C_Ds of 250 and 275-mg ml^-1, suggesting formation of a second uniform, aligned phase. Resonance broadening indicative of another phase transition was again observed at a C_D of 309-mg ml^-1.Interpretations of lineshape changes in terms of phase transitions were supported by microscope examination. Liquid-crystalline phases are traditionally characterized by their microscopic textures as observed through crossed polarizers^19-21. Cholesteric liquid crystals, in which the long axes of the molecules lie in pseudo-planes that are slightly twisted with respect to each other, have periodic variations in refractive index and fringe patterns with spacing of P/2, where P is the cholesteric pitch. Many smectic liquid crystals show focal-conic fan textures due to ordering in a second dimension, and can be easily distinguished from nematic or cholesteric forms^20,21.Three distinct phases were observed simultaneously by placing a 100mg DNA ml^-1 sample on a slide and partially sealing the coverslip, allowing slow evaporation to create a gradient in C_D across the slide (Fig. 2 a,c). The low C_D mesophase was weakly birefringent and gave roughly circular patterns of broad alternating light and dark lines when viewed through crossed polarizers (Fig. 2 a,b). Rapid, small-scale changes in birefringence due to fluctuations in the nematic director were noted at high magnification (x400). The weak birefringence and director fluctuations imply a dynamic character of this phase. Thicker specimens of this phase had an `oily streak’ texture and could be magnetically aligned, but were easily perturbed when removed from the field.

Figure 3(a&b)

Figure 3(c)

We tentatively refer to the first mesophase as a `precholesteric’ phase. A weakly birefringent precholesteric mesophase in moderately concentrated samples of high relative molecular mass DNA was recently reported<sup>19</sup>. The textures of the latter phase were attributed to a three-dimensional helicoidal arrangement of DNA molecules somewhat analogous to the molecular arrangement in blue phases of small molecules. Microscopic textures we observed for the precholesteric phase of short DNA were unlike those reported<sup>19</sup>, suggesting that evolution of DNA phases may be molecular-length dependent.The periodic fringe and `oily streak’ textures of the first mesophase are reminiscent of a cholesteric phase, but they differed significantly from the classical cholesteric textures of the intermediate DNA mesophase, which was highly birefringent with very regular, finely spaced fringe patterns and was extensively aligned in a magnetic field (Fig. 2d). Freeze-fracture-etch electron microscopy and optical diffraction studies have confirmed that this intermediate phase is, in fact, cholesteric (M.W. Davidson and R. L. Rill, manuscript in preparation).Smectic phases have two-dimensional order, with the molecules arranged in planes at a defined angle to the preferred orientation direction of the long molecular axes. There are two common `natural’ textures of smectic a and several other smectic phases-a uniform, homeotropic texture with molecules oriented nearly perpendicular to the slide surface, and the focal-conic fan texture^20,21. Focal-conic and striated fan textures were observed for the highest concentration mesophase (s) in controlled drying experiments (Fig. 2 c,e, and f). Close examination of a 350 mg DNA ml^-1 sample confirmed that DNA forms a mesophase with molecular layering resembling that found in smectic phases of small molecules.Specimens observed immediately after placement on a slide usually exhibited a nearly uniform homeotropic texture. Batonnets initiated after a few hours, enlarged, and eventually merged to yield a classical focalconic fan texture (Fig. 3). Examination in the electron microscope of freeze-fracture-etch replicas confirmed that DNA molecules were arranged in layers, and that the long molecular axes were approximately perpendicular to the layer planes (Fig. 4). More definitive data are required to unambiguously relate this DNA phase to conventional smectics.

Figure 4

Using light and electron microscopy we observed several other textures in samples of ~300-400 mg ml^-1 (for example, compare Fig. 2 e,f), suggesting the existence of other higher-order phases. As DNA is chiral and packs hexagonally in crystals²², chiral phases could form which are analogous to the chiral smectic C phase, or to more ordered chiral hexatic phases of small molecules (for example, chiral smectic G or I (refs 20,21). These observations demonstrate that DNA in vitro can assume multiple-packing arrangements, which can be readily altered over small ranges of concentration. We expect that the phase behavior of DNA in vitro will also be a sensitive function of the ionic environment. Significant modulation of DNA packing in vivo may be accomplished by small changes in DNA concentration of counterion atmosphere. Similar principles may apply to the ordering of other biological polyelectrolytes.We thank Dr. Henry Aldrich of the University of Florida for assistance with freeze-fracture-etch methods and Drs. David Van Winkle and Francoise Livolant for advice on liquid crystal theory. This work was supported in part by the NIH.

REFERENCES

1. Du Praw, E.J. DNA and Chromosomes (Holt, Rinehart & Winston, New York, 1970).

2. Earnshaw, W.C. & Casjens, S.R. Cell 21, 319-331 (1980).

3. Sipski, W. & Wagner, T.E. Biopolymers 16, 573-582 (1977).

4. Onsager, L. Ann. N.Y. Acad. Sci.51, 627-659 (1949).

5. Flory, P.J. Proc. R. Soc. A234, 60-89 (1956).

6. Flory, P.J. in Polymer Liquid Crystals (eds. Ciferri, A., Krigbaum, W.R. & Meyer, R.B.) 103-112 (Academic, New York, 1982).

7. Robinson, C. Trans Faraday Soc. 52, 571-592 (1956).

8. Miller, W.A. Rev. Biophys. 29, 519-535 (1979).

9. Manning, G.S.Q. Rev. Biophys. 11, 170-246 (1978).

10. Stigter, D. Biopolymers 16, 1435-1448 (1977).

11. Stigter, D. J. phys. Chem. 82, 1603-1606 (1978).

12. Brian, A.A., Frisch, H.L. & Lerman, L. S. Biopolymers 20, 1305-1328 (1981).

13. LeBret, M. & Zimm, B. H. Biopolymers 23, 271-285 & 286-312 (1984).

14. Rill, R. L., Hilliard, P.R. & Levy, G.C. J. biol. Chem. 258, 250-256 (1983).

15. Rill, R.L. Proc. natn. Acad. Sci. U.S.A. 83, 342-346 (1986).

16. Strzelecka, T. E. & Rill, R. L. J. Am. chem. Soc. 109, 4513-4518 (1987).

17.. Brandes, R. & Kearns, E. R. Biochemistry 25, 5890-5895 (1986).

18. Lerman, L.S. Cold Spring Harbor Symp. quant. Biol. 38, 59-74 (1974).

19. Livolant, F. J. Physique 48, 1051-1066 (1987).

20. Demus, D. & Richter, L. Textures of Liquid Crystals (Verlag Chemie, New York, 1978).

21.Gray, G.W. & Goodby, J.W.G. Smectic Liquid Crystals (Heyden, Philadelphia, 1984).

22. Lerman, L.S. Wilkerson, L.S., Venable, J.H. J. molec. Biol. 108, 271-293 (1976).

The flood believed to be behind the Noah’s Ark myth kick-started European agriculture, according to new research by the Universities of Exeter, UK and Wollongong, Australia. New research assesses the impact of the collapse of the North American (Laurentide) Ice Sheet, 8000 years ago. The results indicate a catastrophic rise in global sea level led to the flooding of the Black Sea and drove dramatic social change across Europe.

Photo: According to press materials supplied by Shamrock — The Trinity Corporation, this satellite view shows Noah’s Ark jutting out from the snow on Mt. Ararat. Image Courtesy of Digital Globe Satellite photos of Mount Aratat, Turkey taken by commercial imaging satellite company Digital Globe released today are said to contain proof of the existence of the biblical Noah’s Ark.

The research team argues that, in the face of rising sea levels driven by contemporary climate change, we can learn important lessons from the past.

The collapse of the Laurentide Ice Sheet released a deluge of water that increased global sea levels by up to 1.4 metres and caused the largest North Atlantic freshwater pulse of the last 100,000 years. Before this time, a ridge across the Bosporus Strait dammed the Mediterranean and kept the Black Sea as a freshwater lake. With the rise in sea level, the Bosporus Strait was breached, flooding the Black Sea.

This event is now widely believed to be behind the various folk myths that led to the biblical Noah’s Ark story. Archaeological records show that around this time there was a sudden expansion of farming and pottery production across Europe, marking the end of the Mesolithic hunter-gatherer era and the start of the Neolithic. The link between rising sea levels and such massive social change has previously been unclear.

The researchers created reconstructions of the Mediterranean and Black Sea shoreline before and after the rise in sea levels. They estimated that nearly 73,000 square km of land was lost to the sea over a period of 34 years. Based on our knowledge of historical population levels, this could have led to the displacement of 145,000 people. Archaeological evidence shows that communities in southeast Europe were already practising early farming techniques and pottery production before the Flood. With the catastrophic rise in water levels it appears they moved west, taking their culture into areas inhabited by hunter-gatherer communities.

Professor Chris Turney of the University of Exeter, lead author of the paper, said: “People living in what is now southeast Europe must have felt as though the whole world had flooded. This could well have been the origin of the Noah’s Ark story. Entire coastal communities must have been displaced, forcing people to migrate in their thousands. As these agricultural communities moved west, they would have taken farming with them across Europe. It was a revolutionary time.”

Quaternary Science Reviews Volume 26, Issues 17-18, September 2007, Pages 2036-2041
doi:10.1016/j.quascirev.2007.07.003

Catastrophic early Holocene sea level rise, human migration and the Neolithic transition in Europe

Chris S.M. Turney^{a, b, ,} and Heidi Brown
^aSchool of Geography, Archaeology and Earth Resources, University of Exeter, Exeter, EX4 4RJ, UK
^bGeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia

Abstract

The collapse of the Laurentide Ice Sheet and release of freshwater 8740–8160 years ago abruptly raised global sea levels by up to 1.4 m. The effect on human populations is largely unknown. Here we constrain the time of the main sea level rise and investigate its effect on the onset of the Neolithic across Europe. An analysis of radiocarbon ages and palaeoshoreline reconstruction supports the hypothesis that flooding of coastal areas led to the sudden loss of land favoured by early farmers and initiated an abrupt expansion of activity across Europe, driven by migrating Neolithic peoples.
The rise in global sea levels 8000 years ago is in-line with current estimates for the end of the 21st century. Professor Chris Turney continued: “This research shows how rising sea levels can cause massive social change. 8,000 years on, are we any better placed to deal with rising sea levels? The latest estimates suggest that by AD 2050, millions of people will be displaced each year by rising sea levels. For those people living in coastal communities, the omen isn’t good.”

SFI researcher Samuel Bowles and colleague Jung-Kyoo Choi of Kyungpook National University in South Korea suggest that the altruistic and warlike aspects of human nature may have a common origin.

Altruism–benefiting fellow group members at a cost to oneself–and parochialism–hostility toward individuals not of one’s own ethnic, racial, or other group–are common to human nature, but we don’t immediately think of them as working together hand in hand. In fact the unexpected combination of these two behaviors may have enabled the survival of each trait according to Bowles and Choi.

They show that the two behaviors–which they term “parochial altruism”– may have in fact coevolved. On the face of it joining parochialism to altruism is puzzling from an evolutionary perspective because both behaviors reduce one’s payoffs by comparison to what one would gain by avoiding them.

Aggression consumes resources and risks death; altruism, particularly toward those with whom we have no direct relationship, has the effect of helping other genes advance at our expense. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to the success of these conflicts.

Using game theoretic analysis and agent-based simulations Bowles and Choi show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans neither parochialsim nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

“But even if a parochial form of altruism may be our legacy,” said Bowles, “it need not be our fate.” He pointed to the many examples of contemporary altruism extending beyond group boundaries, and the fact that hostility toward outsiders is often redirected or eliminated entirely in a matter of years.

Science. 2007 Oct 26;318(5850):636-640.

The Coevolution of Parochial Altruism and War.

Choi JK, Bowles S.

School of Economics and Trade, Kyungpook National University, 1370 Sankyuk-dong, Buk-gu, Daegu 702-701, Korea.

Altruism-benefiting fellow group members at a cost to oneself-and parochialism-hostility toward individuals not of one’s own ethnic, racial, or other group-are common human behaviors. The intersection of the two-which we term “parochial altruism”-is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one’s payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

see also:

Altruistic Rats: First Evidence For Generalized Reciprocal Cooperation In Non-humans