A Bit More Detail

• 80 Beats suggests that, contrary to expectations, the climate of northern Africa's Sahara region may have been pleasant enough to let early hominids migrate to the Mediterranean basin without being forced to follow the thin fertile strip of the Nile.


• At Acts of Minor Treason, Andrew Barton uses an artifact--his grandfather's old toolbox, a former ammunition box--to wonder about all the things in history that remain unknown, and how speculations about possibilities make alternative history interesting.


• blogTO points out that the current risible anti-drug campaign on the TTC--look, if you do drugs you'll no longer look pretty--is, in fact, risible.
  
• Centauri Dreams commemorates the dream of the generation starship, put forward by Leslie Shepherd in 1952.


• At Crooked Timber, John Quiggin thinks that it might be worthwhile for the United States, at least, to spend more money on education and health than on the military. In the past generation, American military expeditions haven't met very successful outcomes (cf Iraq, Afghanistan).


• Extraordinary Observations' Rob Pitingolo points to a recent study suggesting that, for nine major American cities, the outer suburbs are more dangerous than the inner cities. This, he points out, is a recent change.


• Far Outliers has an interesting excerpt relating to NGOs as "benevolent colonialists."


• The Grumpy Sociologist documents the apparently successful efforts of the National Basketball Association to boost that sport in first China then India, starting with high-profile stars from those countries (Yao Ming, say) to create perceived needs for those sports.


• Itching for Eestimaa suggests that turmoil in Estonia's Centre Party--a left-wing party with strong appeal to Russophones as well as to ethnic Estonians, beset by controversy suggesting that the leader has been accepting Russian money--is the product of a palace coup against the party's leader.


• Lawyers, Guins and Money's Charli Carpenter links to a Financial Times essay by Parag Khanna saying that the world is becoming "neo-medieval," the 21st century coming to resemble the 12th century. The analogy works, actually, save in the many, many ways in which the two centuries are fundamentally different. Argh.


• At NewAPPSBlog, Catarina Dutilh Novaes counsels prospective graduate students against making the jump if they'll go into debt, arguing that the exloitative nature of universities' employment of doctoral students in most countries just isn't worth the payoff: there aren't that many jobs, they don't pay that much.


• Savage Minds shows telepresence in action, with Filipino teachers of English animating avatars in out-of-the-way area of South Korea.


• Towleroad carries the news that, famed failed Tea Party candidate Christine O'Donnell is being investigated for using campaign funds to cover personal expenses like rent.


• Understanding Society's Daniel Little has an interesting post up about dystopian representations of Indians and Chinese cities in film.


• Windows on Eurasia suggests that, under Iranian influence, Shi'ite Islam is taking off in traditionally Sunni but Persian-speaking Tajikistan.

Put simply, our minds are not designed to allow us to have more than a very limited number of people in our social world. The emotional and psychological investments that a close relationship requires are considerable, and the emotional capital we have available is limited.

Indeed, no matter what Facebook allows us to do, I have found that most of us can maintain only around 150 meaningful relationships, online and off — what has become known as Dunbar’s number. Yes, you can “friend” 500, 1,000, even 5,000 people with your Facebook page, but all save the core 150 are mere voyeurs looking into your daily life — a fact incorporated into the new social networking site Path, which limits the number of friends you can have to 50.

What’s more, contrary to all the hype and hope, the people in our electronic social worlds are, for most of us, the same people in our offline social worlds. In fact, the average number of friends on Facebook is 120 to 130, just short enough of Dunbar’s number to allow room for grandparents and babies, people too old or too young to have acquired the digital habit.

This isn’t to say that Facebook and its imitators aren’t performing an important, even revolutionary, task — namely, to keep us in touch with our existing friends.

Until relatively recently, almost everyone on earth lived in small, rural, densely interconnected communities, where our 150 friends all knew one another, and everyone’s 150 friends list was everyone else’s.

But the social and economic mobility of the past century has worn away at that interconnectedness. As we move around the country and across continents, we collect disparate pockets of friends, so that our list of 150 consists of a half-dozen subsets of people who barely know of one another’s existence, let alone interact.

The researchers measured two social network factors in 58 adults. First, they calculated the size of a participant’s network, which is simply the total number of people who are in regular contact with the participant. Second, they measured the network’s complexity, based on how many different groups a participant’s contacts can be divided into. The authors then examined how well those two factors correlated with the size of a participant’s amygdala and hippocampus. The hippocampus served as a negative control, as it should not vary based on social networks.

Linear regression revealed a positive correlation in amygdala size with both social network size and complexity. This effect showed no lateralization, meaning both left and right amygdala volumes followed this relationship. In addition, the effect is relatively specific, as other social factors like life satisfaction and perceived social support failed to correlate with amygdala volume.

Social network size and complexity did not significantly correspond with the size of the hippocampus or other subcortical areas. The authors did find that three regions in the cerebral cortex of the brain (caudal inferior temporal sulcus, caudal superior frontal gyrus, and subgenual anterior cingulate cortex) might correlate with social networks. They propose that those regions might have evolved along with amygdala to deal with the complexities of growing social circles.

Researchers sequencing Neandertal DNA have concluded that between 1 and 4 percent of the DNA of people today who live outside Africa came from Neandertals, the result of interbreeding between Neandertals and early modern humans.

A team of scientists led by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig pieced together the first draft of the sequence—which represents about 60 percent of the entire genome—using DNA obtained from three Neandertal bones that come from Vindija cave in Croatia and are more than 38,000 years old. The researchers detail their analysis of the sequence in the May 7 Science.

The evidence that Neandertals contributed DNA to modern humans came as a shock to the investigators. “First I thought it was some kind of statistical fluke,” Pääbo remarked during a press teleconference on May 5. “We as a consortium came into this with a very, very strong bias against gene flow,” added team member David Reich of Harvard University. But when the researchers conducted additional analyses, the results all pointed to the same conclusion.

The finding contrasts sharply with Pääbo's previous work. In 1997 he and his colleagues sequenced the first Neandertal mitochrondrial DNA . Mitochondria are the cell’s energy-generating organelles, and they have their own DNA that is distinct from the much longer DNA sequence that resides in the cell’s nucleus. Their analysis revealed that Neandertals had not made any contributions to modern mitochondrial DNA. Yet because mitochondrial DNA represents only a tiny fraction of an individual’s genetic makeup, the possibility remained that Neandertal nuclear DNA might tell a different story. Still, additional genetic analyses have typically led researchers to conclude that Homo sapiens arose in Africa and replaced the archaic humans it encountered as it spread out from its birthplace without mingling with them.

But mingle they apparently did, according to the new study. When Pääbo’s team looked at patterns of nuclear genome variation in present-day humans, it identified 12 genome regions where non-Africans exhibited variants that were not seen in Africans and that were thus candidates for being derived from the Neandertals, who lived not in Africa but Eurasia. Comparing those regions with the same regions in the newly assembled Neandertal sequence, the researchers found 10 matches, meaning 10 of these 12 variants in non-Africans came from Neandertals. (Where the other two segments came from remains unknown.)

Intriguingly, the researchers failed to detect a special affinity to Europeans—a link that might have been expected given that Neandertals seem to have persisted in Europe longer than anywhere else before disappearing around 28,000 years ago. Rather the Neandertal sequence was equally close to sequences from present-day people from France, Papua New Guinea and China, even though no Neandertal specimens have turned up in the latter two parts of the world. By way of explanation, the investigators suggest that the interbreeding occurred in the Middle East between 45,00 and 80,000 years ago, before moderns fanned out to other parts of the Old World and split into different groups.

Two Neandertal fossils excavated from Vindija Cave in Croatia in 1998, believed to be the last surviving Neandertals, may be 3,000-4,000 years older than originally thought.

An international team of researchers, including Erik Trinkaus, Ph.D., the Mary Tileston Hemenway Professor of Anthropology in Arts & Sciences, has redated the two Neandertals from Vindija Cave. The results were published in the Jan. 2-6 early edition of the journal Proceedings of the National Academy of Sciences (PNAS).

Other scientists involved were Tom Higham and Christopher Bronk Ramsey of the Oxford University radiocarbon laboratory, Ivor Karavanic of the University of Zagreb and Fred Smith of Loyola University.

The resultant ages are between 32,000-33,000 years old, and perhaps slightly older.

In 1998, the fossils had been radiocarbon dated to 28,000-29,000 years ago.

Rather than taking some 7,000 years to colonize Europe from Africa, the reinterpreted data shows the process may only have taken 5,000 years, scientist Paul Mellars from Cambridge University said in the science journal Nature on Wednesday.

"The same chronological pattern points to a substantially shorter period of chronological and demographic overlap between the earliest ... modern humans and the last survivors of the preceding Neanderthal populations," he wrote.

The reassessment is based on advances in eliminating modern carbon contamination from ancient bone fragments and recalibration of fluctuations in the pattern of the earth's original carbon 14 content.

Populations of anatomically and behaviorally modern humans first appeared in the near eastern region some 45,000 years ago and slowly expanded into southeastern Europe.

Previously it was thought that this spread took place between 43,000 and 36,000 years ago, but the re-evaluated data suggests that it actually happened between 46,000 and 41,000 years ago -- starting earlier and moving faster.