Non facciamo più le asce di una volta.

Un interessante esperimento di Archeologia Sperimentale, sotto controllo neurofisiologico strumentale, che dimostra ineluttabilmente come alcuni strumenti di pietra, che oggi noi consideriamo primitivi (l'ascia a mano dell'Aculeano [500.000 anni fa], per esempio), hanno richiesto l'evoluzione di un pensiero progettuale complesso e non solamente il caso. 
E sei studenti di Archeologia, pur ricostruendo - durante un corso apposito di 18 mesi - una loro ascia a mano, non sono riusciti a produrne di buona qualità, a livello dei nostri comuni predecessori: le loro asce non avrebbero funzionato.
Si è inoltre visto strumentalmente che la pianificazione della costruzione stimola e chiama in causa aree differenti del cervello umano, interessando sia le aree motorie, sia  quelle del 'pensiero strategico', cioé quelle che utilizziamo nello scegliere il migliore percorso automobilistico oggi.
Non era un'attività tanto 'primitiva', insomma...

Complex cognition shaped the Stone Age hand-axe 

The ability to make a Lower Palaeolithic hand axe depends on complex cognitive control by the prefrontal cortex, including the "central executive" function of working memory, a new study finds. 

Handaxes produced for the first (left) and last (right) evaluations, ranked by T3 fMRI task  performance (circled numbers) 

[Credit: Dietrich Stout et al. PLoS One,  2015 DOI: 10.1371/journal.pone.0121804] 

PLOS ONE published the results, which knock another chip off theories that Stone Age hand axes are simple tools that don't involve higher-order executive function of the brain.

 "For the first time, we've showed a relationship between the degree of prefrontal brain activity, the ability to make technological judgments, and success in actually making stone tools," says Dietrich Stout, an experimental archaeologist at Emory University and the leader of the study. 
"The findings are relevant to ongoing debates about the origins of modern human cognition, and the role of technological and social complexity in brain evolution across species." 
The skill of making a prehistoric hand axe is "more complicated and nuanced than many people realize," Stout says. 
"It's not just a bunch of ape-men banging rocks together. We should have respect for Stone Age tool makers." The study's co-authors include Bruce Bradley of the University of Exeter in England, Thierry Chaminade of Aix-Marseille University in France; and Erin Hecht and Nada Khreisheh of Emory University.

Stone tools -- shaped by striking a stone "core" with a piece of bone, antler, or another stone -- provide some of the most abundant evidence of human behavioral change over time. 

Simple Oldowan stone flakes are the earliest known tools, dating back 2.6 million years. 

The Late Acheulean hand axe goes back 500,000 years. 

While it's relatively easy to learn to make an Oldowan flake, the Acheulean hand axe is harder to master, due to its lens-shaped core tapering down to symmetrical edges. 

"We wanted to tease apart and compare what parts of the brain were most actively involved in these stone tool technologies, particularly the role of motor control versus strategic thinking," Stout says. 

The researchers recruited six subjects, all archaeology students at Exeter University, to train in making stone tools, a skill known as "knapping." 
The subjects' skills were evaluated before and after they trained and practiced. 

For Oldowan evaluations, subjects detached five flakes from a flint core. 

For Acheulean evaluations, they produced a tool from a standardized porcelain core. 

At the beginning, middle and end of the 18-month experiment, subjects underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) scans of their brains while they watched videos. 

The videos showed rotating stone cores marked with colored cues: A red dot indicated an intended point of impact, and a white area showed the flake predicted to result from the impact. The subjects were asked the following questions:

- "If the core were struck in the place indicated, is what you see a correct prediction of the flake that would result?"

- "Is the indicated place to hit the core a correct one given the objective of the technology?" 

The subjects responded by pushing a "yes" or "no" button. 
Answering the first question, how a rock will break if you hit it in a certain place, relies more on reflexive, perceptual and motor-control processes, associated with posterior portions of the brain. 
Stout compares it to the modern-day rote reflex of a practiced golf swing or driving a car. 

The second question -- is it a good idea to hit the core in a certain spot if you want to make a hand axe -- involves strategic thinking, such as planning the route for a road trip. 
"You have to think about information that you have stored in your brain, bring it online, and then make a decision about each step of the trip," Stout says. 
This so-called executive control function of the brain, associated with activity in the prefrontal cortex, allows you to project what's going to happen in the future and use that projection to guide your action. "It's kind of like mental time travel, or using a computer simulation," Stout explains. 

"It's considered a high level, human cognitive capacity." The researchers mapped the skill level of the subjects onto the data from their brain scans and their responses to the questions. 
Greater skill at making tools correlated with greater accuracy on the video quiz for predicting the correct strategy for making a hand axe, which was itself correlated with greater activity in the prefrontal cortex. 
"These data suggest that making an Acheulean hand axe is not simply a rote, auto pilot activity of the brain," Stout says. 
"It requires you to engage in some complicated thinking." 

Most of the hand axes produced by the modern hands and minds of the study subjects would not have cut it in the Stone Age.

 "They weren't up to the high standards of 500,000 years ago," Stout says. A previous study by the researchers showed that learning to make stone tools creates structural changes in fiber tracts of the brain connecting the parietal and frontal lobes, and that these brain changes correlated with increases in performance. "Something is happening to strengthen this connection," Stout says. "This adds to evidence of the importance of these brain systems for stone tool making, and also shows how tool making may have shaped the brain evolutionarily." 
Stout recently launched a major, three-year archaeology experiment that will build on these studies and others. 
Known as the Language of Technology project, the experiment involves 20 subjects who will each devote 100 hours to learning the art of making a Stone Age hand axe, and also undergo a series of MRI scans. 
The project aims to hone in whether the brain systems involved in putting together a sequence of words to make a meaningful sentence in spoken language overlap with systems involved in putting together a series of physical actions to reach a meaningful goal. 


Source: Emory Health Sciences 

[April 15, 2015]

Perché il linguaggio è unicamente umano?

Why is language unique to humans?

New research published today in Journal of the Royal Society Interface suggests that human language was made possible by the evolution of particular psychological abilities. 

A mural in Teotihuacan, Mexico (ca. 200 AD) depicting a person emitting a speech scroll from his mouth, symbolizing speech [Credit: Daniel Lobo/WikiCommonjs]

Researchers from Durham University explain that the uniquely expressive power of human language requires humans to create and use signals in a flexible way. They claim that his was only made possible by the evolution of particular psychological abilities, and thus explain why language is unique to humans.

Using a mathematical model, Dr Thomas Scott-Phillips and his colleagues, show that the evolution of combinatorial signals, in which two or more signals are combined together, and which is crucial to the expressive power of human language, is in general very unlikely to occur, unless a species has some particular psychological mechanisms. Humans, and probably no other species, have these, and this may explain why only humans have language.

In a combinatorial communication system, some signals consist of the combinations of other signals. Such systems are more efficient than equivalent, non-combinatorial systems, yet despite this they are rare in nature. Previous studies have not sufficiently explained why this is the case. The new model shows that the interdependence of signals and responses places significant constraints on the historical pathways by which combinatorial signals might emerge, to the extent that anything other than the most simple form of combinatorial communication is extremely unlikely.

The scientists argue that these constraints can only be bypassed if individuals have the sufficient socio-cognitive capacity to engage in ostensive communication. Humans, but probably no other species, have this ability. This may explain why language, which is massively combinatorial, is such an extreme exception to nature’s general trend.

Authors: Thomas C. Scott-Phillips and Richard A. Blythe | Source:  The Royal Society [September 18, 2013]

Lancio veloce di oggetti ed evoluzione

Elastic energy storage in the shoulder 

and the evolution of high-speed throwing in Homo

• Neil T. Roach,
• Madhusudhan Venkadesan,
• Michael J. Rainbow
• & Daniel E. Lieberman

Nature

 

498,

 

483–486

 

(27 June 2013)

 

doi:10.1038/nature12267

Received

 

11 January 2013 

Accepted

 

02 May 2013 

Published online

 

26 June 2013

Article toCitation

Some primates, including chimpanzees, throw objects occasionally, but only humans regularly throw projectiles with high speed and accuracy. Darwin noted that the unique throwing abilities of humans, which were made possible when bipedalism emancipated the arms, enabled foragers to hunt effectively using projectiles. However, there has been little consideration of the evolution of throwing in the years since Darwin made his observations, in part because of a lack of evidence of when, how and why hominins evolved the ability to generate high-speed throws. Here we use experimental studies of humans throwing projectiles to show that our throwing capabilities largely result from several derived anatomical features that enable elastic energy storage and release at the shoulder. These features first appear together approximately 2  million years ago in the species Homo erectus. Taking into consideration archaeological evidence suggesting that hunting activity intensified around this time, we conclude that selection for throwing as a means to hunt probably had an important role in the evolution of the genus Homo.

L'uomo anatomicamente moderno (U.A.M.) è l'unico primate che lancia velocemente oggetti. Questo lo vediamo quotidianamente negli sport attuali. Ma si tratta di un fattore distintivo dell'evoluzione dell'uomo: probabilmente proprio di uno di quelli che gli ha permesso di giungere ad occupare il posto di assoluta preminenza di oggi. Si tratta di una serie di modifiche dell'anatomia e della funzionalità dei muscoli e delle ossa alla radice dell'arto superiore.La più antica arma da lancio con punta di pietra risale a 500.000 anni fa, circa. Ma l'uomo ha cacciato da almeno 1,5 milioni di anni prima. Il che significa che disponeva solamente di un un bastone appuntito: per uccidere le sue prede, doveva forzatamente lanciarlo con molta, molta forza.

Ability to throw played a key role in human evolution

It's easy to marvel at the athleticism required to throw a 90-mile-per-hour fastball, but when Neil Roach watches baseball, he sees something else at work – evolution.

Throwing at high speeds is unique to humans and it helped Homo erectus to
hunt two millions years ago [Credit: Web]

That ability – to throw an object with great speed and accuracy – is a uniquely human adaptation, one that Roach believes was crucial in our evolutionary past. How, when and why humans evolved the ability to throw so well is the subject of a study published today (June 26) in the journal Nature. 

The study was led by Roach, who recently received his Ph.D. from Harvard's Graduate School of Arts and Sciences and is now a postdoctoral researcher at George Washington University, with Madhusudhan Venkadesan of NCBS at the Tata Institute of Fundamental Research, Michael Rainbow of the Spaulding National Running Center, and Daniel Lieberman, the Edwin M. Lerner II Professor of Biological Sciences at Harvard. 

They found that a suite of changes to our shoulders and arms allowed early humans to more efficiently hunt by throwing projectiles, helping our ancestors become part-time carnivores and paving the way for a host of later adaptations, including increases in brain size and migration out of Africa.

"When we started this research, there were essentially two questions we asked – one of them was why are humans so uniquely good at throwing, while all other creatures including our chimpanzee cousins are not," said Roach. "The other question was: How do we do it? What is it about our body that enables this behavior, and can we identify those changes in the fossil record?"

What they found, Roach said, were a suite of physical changes - such as the lowering and widening of the shoulders, an expansion of the waist, and a twisting of the humerus – that make humans especially good at throwing.

While some of those changes occurred earlier during human evolution, Lieberman said it wasn't until the appearance of Homo erectus, approximately 2 million years ago, that they all appeared together. The same period is also marked by some of the earliest signs of effective hunting, suggesting that the ability to throw an object very fast and very accurately played a critical role in human's ability to rise to the top of the food chain.

"The ability to throw was one of a handful of changes that enabled us to become carnivores, which then triggered a host of changes that occurred later in our evolution," Lieberman said. "If we were not good at throwing and running and a few other things, we would not have been able to evolve our large brains, and all the cognitive abilities such as language that come with it. If it were not for our ability to throw, we would not be who we are today."

Scientists collected motion data from baseball players to uncover why humans are
such good throwers [Credit: George Washington University]

To start unpacking the evolutionary origins of throwing, Roach began not by studying how humans throw, but how our closest relatives – chimpanzees – do.

Though they're known to throw objects (often feces) underhand, chimps, on rare occasions, do throw overhand, but those throws are far less accurate and powerful than those of the average Little League pitcher, Roach said. Additionally, chimps throw as a part of display behavior and never when hunting.

Part of the reason for chimpanzee's poor throwing performance, Lieberman said, is tied to their technique, which in turn is limited by their anatomy. "Chimps throw overhand using either a dart throwing motion, where the elbow is extended, or much like a cricket bowler, where their elbow is kept straight and they generate force by swinging their shoulder", Lieberman said.

"That led us to studying cricket bowlers and trying to understand what happens when you keep your arm straight, and why that diminishes your throwing ability," Roach said. "Eventually, we began to think that changes in the way the shoulder is oriented with regards to the rest of the body could change the way you generate force when you're throwing."

To explore those physical changes, Roach and colleagues began by creating a complex model that incorporated current research about the biomechanics of throwing. Using that model, they were able to explore how morphological changes to the body – wider shoulders, arms that are higher or lower on the body, the ability to twist the upper body independently of the hips and legs, and the anatomy of the humerus – effect throwing performance.

In addition to the modeling, Roach performed a series of real-world experiments in Lieberman's Skeletal Biology Lab using members of the Harvard Baseball team and a host of braces designed to limit their movements.

The idea, Roach explained, was that by restricting certain motions, the players would be forced into a more primitive condition, giving him the opportunity to see how different anatomical shifts contribute to the mechanics of modern throwing.

Armed with a method known as inverse dynamics, Roach and colleagues were able to not only quantify how much restricting certain types of movements affected throwing performance, but were able to trace the effect to specific changes in the mechanics of each player.

"We try to push these bits of anatomy back in time, if you will, to see how that affects performance," Roach said. "The important thing about our experiments is that they went beyond just being able to measure how the restriction affects someone's ability to throw fast and accurately – they allowed us to to figure out the underlying physics. For example, when a thrower's velocity dropped by 10 percent, we could trace that change back to where it occurred."

"In order to test our evolutionary hypotheses, we needed to link the changes we'd seen in the fossil record to performance in terms of throwing," he continued. "This type of analysis allowed us to do that."

What they found were three key physical changes that helped to make fast, accurate throwing possible. 

Evolutionary changes in the shoulder show that, as a pitcher cocks their arm back, "what they're doing is stretching the ligaments and tendons that run across their shoulder," Roach said. "Those tendons and ligaments get loaded up like the elastic bands on a slingshot, and late in the throw they release that energy rapidly and forcefully to rotate the upper arm with extraordinary speed and force." That rotation is the fastest motion the human body can produce. "The rotation of the humerus can reach up to 9,000 degrees-per-second, which generates an incredible amount of energy, causing you to rapidly extend your elbow, producing a very fast throw", Roach said.
Among the evolutionary changes that proved key to generating a powerful throwing motions, he said, was a twist in the bone of the upper arm and an expanded, mobile waist, which both gave early humans the ability to store up and then release more of this elastic energy

"The linchpin is really what's going on with the shoulder," Roach said. "When you see the shift from a chimpanzee shoulder to a more relaxed human-like shoulder, that enables this massive energy storage. Many of the evolutionary changes we studied, whether in the torso or the wrist, may predate Homo erectus, but when we see that final change in the shoulder, that's what brings it all together."

While the findings help shed light on a critical phase of human evolution, they also hint at a possible solution to a hotly debated question in sports: When it comes to young players, how much throwing is too much?

"It's a tough question to answer," Roach said. "The real difference, from an evolutionary perspective, is the frequency with which some folks throw now. To successfully learn to throw and use that ability to hunt, our ancestors would need to throw often, but nothing like the 100 or more high speed throws that some baseball pitchers throw now in the span of a couple of hours."

"I think it's really a case of what we evolved to do being superseded by what we're now asking athletes to do," he continued. "Athletes are overusing this capability that gave early humans an evolutionary advantage, and they're overusing it to the point that injuries are common."

Ultimately, Lieberman said, the evidence points to one clear conclusion – the ability to throw with speed and accuracy is a uniquely human adaptation, one that played an immeasurably important role in human development.

"Recent research indicates that stone points – the oldest kind of spear point – are about 500,000 years old," he said. "But people have been killing animals for at least 2 million years, and eating animals for about 2.6 million years."
"That means that for about 1.5 million years, when people hunted, they basically had nothing more lethal to throw than a pointed wooden stick," he continued. "If you want to kill something with that, you have to be able to throw that pretty hard, and you have to be accurate. Imagine how important it must have been to our ancestors to throw hard and fast." 

Source: Harvard University [June 26, 2013]

Evoluzione dell'Uomo

'Much-derided theory' of human evolution from aquatic apes resurfaces

Scientists, academics and medics gathered this week in a London hotel to discuss a topic that has been virtually unmentionable in academic circles for decades - did humans descend from "aquatic apes" that spent more time swimming than dragging their knuckles on the ground?

A female western lowland gorilla walks through a river. Some scientists believe our
ancestors lived an aquatic lifestyle [Credit: Getty images]

The last time this question was asked, at a conference in 1992, there was much scoffing and ridicule. Other academics sneered and Bernard Levin wrote a full-page article lampooning the idea in a national newspaper, the Independent reported.

This week's conference, Human Evolution Past, Present and Future - Anthropological, Medical and Nutritional Considerations, at the Grange St Paul's Hotel, has also already been the subject of much derision.

Followers of the conventional and overwhelmingly accepted belief that our ancestors were very much land-based are launching a parody campaign online to argue we evolved from "space monkeys".

Most scientists will openly scoff at the idea of us deriving from water-bound primates.

But, perhaps emboldened by the presence of Sir David Attenborough - who was booked to attend the conference for one session but asked at the last minute if he could attend both days - the aquatic ape theorists are back.

The conference is chaired by Professor Rhys Evans, an ear, nose and throat surgeon at the Royal Marsden Hospital, who is candid about the scope of the conference.

"We are trying to discuss the pros and cons of the theory," he said.

"But many of the things which are unique to humans - such as a descended larynx, walking upright, fat beneath the skin, and most obviously an extremely large brain - it seems can best be accounted for as adaptations to extended periods in an aquatic environment," he added.

The original aquatic ape theory, developed by Sir Alister Hardy and made public in 1960, posited that a population of early humans, or hominoids, was isolated during tectonic upheaval in a flooded forest environment, similar to that of parts of the Amazon.

Our ancestors, it was argued, either adapted to water - and climbing in trees - or died out.

Over many generations, mutations that made swimming and diving easier reproduced in the population at the expense of the more traditional, water-averse ape genes.

Modern-day apes do not like water. In zoos all around the world, apes are contained by moats of water.

Even wadeable moats are sufficient: if you drop a baby orangutan into water, it sinks like a stone.

A human baby, however, will close its larynx and automatically paddle its arms and legs, giving you a few precious seconds to retrieve it.

The aquatic ape theory would explain this ability - unlike the traditional savannah theory of human evolution.

Widely accepted wisdom states that when humans came out of the woods and on to the savannah, walking upright gave them an increased field of vision and freed up hands to use tools.

Bipedalsim also exposed less of the human body to the harsh sun and humans shed hair and increased sweat production to cope with the heat.

But, the aquatic ape proponents point out, deer and antelope kept their fur and their quadrapedal ways on the savannah.

Our copious salty sweat production, and water consumption requirements, they argue, are far more indicative of life in the water. 

Source: ANI [May 09, 2013]