Tuesday, May 24, 2011

A distinct presence of African ancestry in Southern European, Middle Eastern and Jewish populations.


Population genetics reveals shared ancestries

More than just a tool for predicting health, modern genetics is upending long-held assumptions about who we are. A new study by Harvard researchers casts new light on the intermingling and migration of European, Middle Eastern and African and populations since ancient times.

In a paper titled "The History of African Gene Flow into Southern Europeans, Levantines and Jews," published in PLoS Genetics, HMS Associate Professor of Genetics David Reich and his colleagues investigated the proportion of sub-Saharan African ancestry present in various populations in West Eurasia, defined as the geographic area spanning modern Europe and the Middle East. While previous studies have established that such shared ancestry exists, they have not indicated to what degree or how far back the mixing of populations can be traced.

Analyzing publicly available genetic data from 40 populations comprising North Africans, Middle Easterners and Central Asians were doctoral student Priya Moorjani and Alkes Price, an assistant professor in the Program in Molecular and Genetic Epidemiology within the Department of Epidemiology at the Harvard School of Public Health.

Moorjani traced genetic ancestry using a method called rolloff. This platform, developed in the Reich lab, compares the size and composition of stretches of DNA between two human populations as a means of estimating when they mixed. The smaller and more broken up the DNA segments, the older the date of mixture.

Moorjani used the technique to examine the genomes of modern West Eurasian populations to find signatures of Sub-Saharan African ancestry. She did this by looking for chromosomal segments in West Eurasian DNA that closely matched those of Sub-Saharan Africans. By plotting the distribution of these segments and estimating their rate of genetic decay, Reich's lab was able to determine the proportion of African genetic ancestry still present, and to infer approximately when the West Eurasian and Sub-Saharan African populations mixed.

"The genetic decay happens very slowly," Moorjani explained, "so today, thousands of years later, there is enough evidence for us to estimate the date of population mixture."

While the researchers detected no African genetic signatures in Northern European populations, they found a distinct presence of African ancestry in Southern European, Middle Eastern and Jewish populations. Modern southern European groups can attribute about 1 to 3 percent of their genetic signature to African ancestry, with the intermingling of populations dating back 55 generations, on average—that is, to roughly 1,600 years ago. Middle Eastern groups have inherited about 4 to 15 percent, with the mixing of populations dating back roughly 32 generations. A diverse array of Jewish populations can date their Sub-Saharan African ancestry back roughly 72 generations, on average, accounting for 3 to 5 percent of their genetic makeup today.

According to Reich, these findings address a long-standing debate over African multicultural influences in Europe. The dates of population mixtures are consistent with documented historical events. For example, the mixing of African and southern European populations coincides with events during the Roman Empire and Arab migrations that followed. The older-mixture dates among African and Jewish populations are consistent with events in biblical times, such as the Jewish diaspora that occurred in 8th to 6th century BC.

"Our study doesn't prove that the African ancestry is associated with migrations associated with events in the Bible documented by archeologists," Reich says, "but it's interesting to speculate."

Reich was surprised to see any level of shared ancestry between the Ashkenazi and non-Ashkenazi Jewish groups. "I've never been convinced they were actually related to each other," Reich says, but he now concludes that his lab's findings have significant cultural and genetic implications. "Population boundaries that many people think are impermeable are, in fact, not that way."

Monday, May 23, 2011

Why We Walk Upright and Why Women Like Tall Men


Standing Up to Fight: Does It Explain Why We Walk Upright and Why Women Like Tall Men?

Complete article

A University of Utah study shows that men hit harder when they stand on two legs than when they are on all fours, and when hitting downward rather than upward, giving tall, upright males a fighting advantage.

This may help explain why our ape-like human ancestors began walking upright and why women tend to prefer tall men.

"The results of this study are consistent with the hypothesis that our ancestors adopted bipedal posture so that males would be better at beating and killing each other when competing for females," says David Carrier, a biology professor who conducted the study. "Standing up on their hind legs allowed our ancestors to fight with the strength of their forelimbs, making punching much more dangerous."

"It also provides a functional explanation for why women find tall men attractive," Carrier adds. "Early in human evolution, an enhanced capacity to strike downward on an opponent may have given tall males a greater capacity to compete for mates and to defend their resources and offspring. If this were true, females who chose to mate with tall males would have had greater fitness for survival."

Carrier's new study is being published May 18 in the online Public Library of Science journal PLoS ONE.

The idea is not new that fighting and violence played a role in making human ancestors shift from walking on all fours to walking on two legs. But Carrier's new study physically demonstrates the advantage of fighting from an upright, two-legged posture.

Carrier measured the force of punches by male boxers and martial arts practitioners as they hit in four different directions: forward, sideways, down and up.

A punching bag fitted with a sensor measured the force of forward and sideways punches. For strikes downward and upward, the men struck a heavy padded block on the end of a lever that swung up and down because it was suspended from an axle.

In either case, the men struck the target as hard as they could both from a standing posture and on their hands and knees.

The findings: for all punching angles, men hit with far more force when they were standing, and from both postures they could hit over twice as hard downward as upward.

Humans: Two-Legged Punching Apes?

The transition from four-legged to two-legged posture is a defining point in human evolution, yet the reason for the shift is still under debate. Darwin thought that our ancestors stood up so they could handle tools and weapons. Later scientists have suggested that bipedalism evolved for a host of other reasons, including carrying food, dissipating heat, efficient running and reaching distant branches while foraging in trees.

"Others pointed out that great apes often fight and threaten to fight from bipedal posture," says Carrier. "My study provides a mechanistic explanation for why many species of mammals stand bipedally to fight."

Carrier says many scientists are reluctant to consider an idea that paints our ancestors as violent.

"Among academics there often is resistance to the reality that humans are a violent species. It's an intrinsic desire to have us be more peaceful than we are," he says.

Nevertheless, human males and their great ape cousins -- chimpanzees, gorillas and orangutans -- frequently fight each other for territory and access to females.

The most popular theories about why we became bipedal are based on locomotor advantages -- increases in the efficiency of walking and running. However, research shows upright posture is worse for locomotion, contrary to what Carrier initially believed.

"If you're a chimpanzee- or gorilla-type ancestor that is moving on the ground, walking bipedally has a cost," he says. "It's energetically more expensive, it's harder to speed up and slow down, and there are costs in terms of agility. In every way, going from four legs to two is a disadvantage for locomotion. So the selective advantage for becoming bipedal, whatever it was, must have been important."

Nearly all mammals, including chimps and gorillas, move on all fours when they run or cover long distances on the ground. On the other hand, all sorts of four-legged animals stand up and use their front legs to fight. They include anteaters, lions, wolves, bears, wolverines, horses, rabbits and many rodents and primates.

Carrier believes that the usefulness of quadruped forelegs as weapons is a side effect of how forelegs are used for walking and running. When an animal is running with its body positioned horizontally, the forelegs strike down at the ground. By lifting the body to a vertical posture, animals can direct that same force toward an opponent.

In addition, quadrupeds are stronger pulling back with their forelimbs than pushing forward. That translates to a powerful downward blow when they rear up on their hind legs. These advantages, which grow directly out of four-legged movement, can be used most effectively by an animal that can stand easily on two legs.

Carrier predicted that animals would hit harder with their forelegs when their bodies were held upright than when they were horizontal, and that they would hit harder downward than upward. Although it would be ideal to test these hypotheses with four-legged animals, humans should still possess the advantages that led our ancestors to stand upright, and they are more practical test subjects.

The results were exactly what Carrier expected. Men's side strikes were 64 percent harder, their forward strikes were 48 percent harder, their downward strikes were 44 percent harder, and their upward strikes were 48 percent harder when they were standing than when they were on their hands and knees. From both postures, subjects delivered 3.3 times as much force when they hit downward rather than upward.

Do Women Want Men Who Can Fight?

While Carrier's study primarily deals with the evolution of upright posture, it also may have implications for how women choose mates. Multiple studies have shown that women find tall men more attractive. Greater height is also associated with health, social dominance, symmetrical faces and intelligence in men and women. These correlations have led some scientists to suggest that women prefer tall men because height indicates "good genes" that can be passed on to offspring. Carrier believes there is more to it.

"If that were the whole story, I would expect the same to be true for men -- that men would be attracted to tall women. But it turns out they're not. Men are attracted to women of average height or even shorter," he says.

The alternative explanation is that tall males among our ancestors were better able to defend their resources, partners and offspring. If males can hit down harder than they can hit up, a tall male has the advantage in a fight because he can punch down to hit his opponent's most vulnerable targets.

Carrier certainly isn't saying women like physically abusive men or those who get into fights with each other. He is saying that women like tall men because tallness is a product if the evolutionary advantage held by our ancestors who began standing upright to fight.

"From the perspective of sexual selection theory, women are attracted to powerful males, not because powerful males can beat them up, but because powerful males can protect them and their children from other males," Carrier says.

"In a world of automatic weapons and guided missiles, male physical strength has little relevance to most conflicts between males," he adds. "But guns have been common weapons for less than 15 human generations. So maybe we shouldn't be surprised that modern females are still attracted to physical traits that predict how their mates would fare in a fight."

Thursday, May 19, 2011

Archaeologists uncover oldest mine in the Americas


Archaeologists have discovered a 12,000-year-old iron oxide mine in Chile that marks the oldest evidence of organized mining ever found in the Americas, according to a report in the June issue of Current Anthropology.

A team of researchers led by Diego Salazar of the Universidad de Chile found the 40-meter trench near the coastal town of Taltal in northern Chile. It was dug by the Huentelauquen people—the first settlers in the region—who used iron oxide as pigment for painted stone and bone instruments, and probably also for clothing and body paint, the researchers say.

The remarkable duration and extent of the operation illustrate the surprising cultural complexity of these ancient people. "It shows that [mining] was a labor-intensive activity demanding specific technical skills and some level of social cooperation transmitted through generations," Salazar and his team write.

An estimated 700 cubic meters and 2,000 tons of rock were extracted from the mine. Carbon dates for charcoal and shells found in the mine suggest it was used continuously from around 12,000 years ago to 10,500 years ago, and then used again around 4,300 years ago. The researchers also found more than 500 hammerstones dating back to the earliest use of the mine.

"The regular exploitation of [the site] for more than a millennium … indicates that knowledge about the location of the mine, the properties of its iron oxides, and the techniques required to exploit and process these minerals were transmitted over generations within the Huentelauquen Cultural Complex, thereby consolidating the first mining tradition yet known in America," the researchers write. The find extends "by several millennia the mining sites yet recorded in the Americas."

Before this find, a North American copper mine dated to between 4,500 and 2,600 years ago was the oldest known in the Americas.

Saturday, May 14, 2011

Last Neanderthals Near the Arctic Circle?


Remains found near the Arctic Circle characteristic of Mousterian culture(1) have recently been dated at over 28,500 years old, which is more than 8,000 years after Neanderthals are thought to have disappeared. This unexpected discovery by an international multi-disciplinary team challenges previous theories. (2) Could Neanderthals have lived longer than thought? Or had Homo sapiens already migrated to Europe at that stage?

The results are published in Science of 13 May 2011.

The distinguishing feature of Mousterian culture, which developed during the Middle Palaeolithic (-300,000 to -33,000 years), is the use of a very wide range of flint tools, mainly by Neanderthal Man in Eurasia, but also by Homo sapiens in the Near East.

This culture is considered to be archaic, and not sufficiently advanced to allow Neanderthals to settle in the most extreme northern climates. It is thought to have brought about their demise some 33,000 to 36,000 years ago. They seem to have made way for modern humans, who appear to have occupied the whole of Eurasia thanks to their mastery of more advanced technologies.

A multi-disciplinary team of French CNRS researchers, working with Norwegian and Russian scientists, studied the Byzovaya site in the Polar Urals in northern Russia. Using carbon 14 dating and an optical simulation technique, the team was able to put an accurate date on sediments and on mammoth and reindeer bones abandoned on the site. The bones bore traces of butchering by Mousterian hunters.

The results intrigue scientists in more ways than one. They show that Mousterian culture may have lasted longer than scientists had originally thought. What's more, no Mousterian presence had ever been identified so close to the Arctic Circle. All other traces are at least 1000 km further south. Lastly, the Byzovaya site, in Eurasia, seems only to have been occupied once, approximately 28,500 years ago, which is over 8,000 years after Neanderthals were thought to have disappeared.

So this discovery raises many questions, not least about how Mousterian society was organised. Did Neanderthal Man live longer than thought? Or could these last bearers of Mousterian culture in fact have been Homo sapiens? If so, the theories explaining that Neanderthals died out because their culture was archaic would be put into question. The studies open up new perspectives on this turning point in human history.

(1) One of the distinctive features of Mousterian culture is the use of particular tools during the Middle Palaeolethic (-300,000 to -33,000 years), both by Neanderthals in Europe and by Homo sapiens in the Near East

(2) Including this one omly a few days old: Neanderthals Died out Earlier Than Previously Thought, New Evidence Suggests

Friday, May 6, 2011

Looking for Sodom: The North Side Story


Complete article and picture

For decades, scientists and scholars have been searching for the fabled cities of Sodom and Gomorrah and the "cities of the Plain", the cities that, according to the Biblical record, were destroyed anciently by God because of the great iniquity of their inhabitants. Recent archaeological investigations, including two currently in progress, are now raising some fascinating prospects that may possibly bring us closer to identifying the location and remains of at least one of these infamous cities, Sodom, the kingpin itself. One of these investigations may overturn long-held theories about where the infamous city was located.

The South Side Story

Traditionally, research has focused on the lands bordering the southeast end of the Dead Sea, where a narrow, arid alluvial plain abuts steeply rising highland areas. Many scholars have interpreted geographic and scriptural references documented in the Biblical account as pointing to this area:

And Lot lifted up his eyes, and beheld all the plain of Jordan, that it was well watered every where, before the Lord destroyed Sodom and Gomorrah, even as the garden of the Lord, like the land of Egypt, as thou comest unto Zoar.

Genesis 13:10

Using Zoar as their operative word, many scholars thus guided themselves by the Biblical and extra-Biblical accounts of Josephus and the ancient Madaba Map as locating Zoar at the southern end of the Dead Sea. Early investigations in the area of Zoar, however, turned up nothing. But a later expedition conducted by Paul Lapp and then continuing excavations beginning in 1975 by Thomas Schaub of Indiana University of Pennsylvania and Walter Rast of Valparaiso University after his death revealed some noteworthy finds. They explored and excavated the remains of four settlements dated to the Early Bronze Age. Excavations at the two largest sites, Bab edh-Dhra and Numeira, turned up a 7-meter stone wall and earlier mudbrick wall, shaft tombs, house remains, and a clear destruction layer. Numerous Early Bronze Age tombs discovered in the area have been suggested to represent burials of as many as 500,000 individuals. Based on the dating, both Bab edh-Dhra and Numeira were destroyed at the same time. Some scholars have proposed that the settlements were destroyed by natural causes. Bab edh-Drha, the largest of the sites, has been advanced by some as a possible candidate for Sodom and the smaller site of Numeira as Gomorrah. Conclusive evidence that the Biblical cities have been found? The jury is still very much out on this one...

The North Side Story

What is now emerging as the most promising new prospect for Sodom, according to a number of scholars, is a site called Tall el-Hammam located approximately 14 kilometers northeast of the Dead Sea in the fertile southern Jordan River Valley of Jordan. Nestled among lush agricultural fields, it is a mound (or Tall) that rises conspicuously from a ground space encompassing one square kilometer, a very large site by any comparison. Dr. Steven Collins of Trinity Southwest University began research related to Sodom by carefully examining the biblical text in Genesis, along with geographic study and intense, broad-based archaeological surveys. All indicators brought him to the location of Tall el-Hammam....Tall el-Hammam represents what is left of the hub of a Bronze Age city-state complex at the cross-roads of major trade routes, rising to prominence as the economic powerhouse in the southern Jordan Valley and influencing and possibly controlling a system of smaller settlements in the region. Generations of kings built palaces, temples, administrative centers, and massive fortifications and defensive walls at this location.

Questions beg for answers. Who were these people and how did they live? How did they relate to the other kingdoms of the Levant, Mesopotamia, and Egypt at the time?

...More detailed information about the Tall el-Hammam excavations and the discoveries can be found at http://www.tallelhammam.com/Tall_el_Hammam.html.