Earliest 'modern' hand nearly two million years old

A tiny, 1.85 million-year-old bone from the little finger of a human ancestor unearthed in East Africa has revealed the oldest "modern" hand ever found, scientists reported Tuesday.

A picture released on August 18, 2015 by Nature Communications shows a OH 86 hominin 
manual proximal phalanx in (from L-R) dorsal, lateral, palmar (distal is top for each) 
and proximal views [Credit: AFP/Rodrigo Dominguez]

The discovery of the pinkie bone pushes back in time a key step in the evolution of our forebear from tree-climbing foragers to tool-wielding hunters, the authors say.

It also hints at the existence of a larger, more human-like creature than others known to have lived at that time in the same region—one of the hotspots of human origin—in modern-day Tanzania.

The hand is one of the critical anatomical features distinguishing humans, and even a 3.6-centimetre (1.5-inch), two-million-year-old fragment can reveal a lot about body type and behaviour.

The shape of our forebears' hands was both a reflection of their stage of evolution, and a driver of that evolution, explained lead author Manuel Dominguez-Rodrigo, a researcher at the Institute of Evolution in Africa in Madrid.

"Our hand evolved to allow us a variety of grips and enough gripping power to allow us the widest range of manipulation observed in any primate," he said by email.

"It is this manipulation capability that interacted with our brains to develop our intelligence, mainly through the invention and use of tools."

A picture released on August 18, 2015 by Nature Communications shows 
an OH 86 hominin phalanx overlaid on a modern human hand
[Credit: AFP/Jason Heaton]

What scientists call "modern human-like" hand anatomy has several defining characteristics.

One is a longer thumb, allowing us to grip more precisely and to open our hands more fully.

Another is the straightening of our phalanges, the general name given to the three bones found in each finger. Curved phalanges were adapted for climbing trees and swinging from branches.

"A modern-like hand in the past would tell us when humans became fully terrestrial and when and how efficiently our ancestors used tools," Dominguez-Rodrigo said.

That transition happened in two main stages.

After the earliest hominins—which includes all members of the Homo genus—began walking on two legs some six million years ago, the hand evolved a longer thumb.

But the fingers remained curved, suggesting that trees remained part of their habitat.

This "double locomotion"—on the ground, through the trees—remained the norm for another four million years.

A picture released on August 18, 2015 by Nature Communications shows people 
excavating the fossiliferous layer at PTK in the Olduvai Gorge, one of the most
 important paleoanthropological sites in the world 
[Credit: AFP/Rodrigo Dominguez]

"I always had trouble understanding how Homo habilis—barely taller than one metre (three feet)—could efficiently hunt animals that big," Dominguez-Rodrigo said.

The existence of a bigger, more modern-looking hominin would help explain this puzzle.

Other experts not involved in the study agreed.

"It brings support to those who challenge the view that Homo habilis was the maker of the stone artifacts becoming abundant in layers of this time period," commented Jean-Jacques Hublin, director of the department of human evolution at the Max Planck Institute for Evolutionary Anthropology.

At the same time, Hublin and others challenged the broad conclusions reached on the basis of such slim evidence.

"One single bone from a pinkie finger does not imply a whole modern human-like skeleton," Hublin said by email.

Another leader in the field, Tracy L. Kivell of the School of Anthropology and Conservation at the University of Kent, was even more sceptical.

"This single bone tells us nothing about what the rest of the hand looked like, let alone what the rest of the skeleton looked like," she told AFP by mail.

"If recent, more complete hominin fossil discoveries have taught us anything, it's that strange combinations of more derived human-like features and more primitive australopith-like features throughout the skeleton are likely the rule, rather than the exception, especially at this time period."

The study has been published by the journal Nature Communications.

Author: Marlowe Hood | Source: AFP [August 18, 2015]

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50,000-year-old human skull found in Siberian cave

Fragments of an early human skull and rib were found in Pleistocene era layers in Strashnaya Cave, it was announced today by Professor Andrey Krivoshapkin, head of Archeology and Ethnography at Novosibirsk State University. These are expected to be 'no younger than 50,000 years' old, he said.

Ancient human remains from a Siberian cave dating back 50,000 years or more
 could provide a missing link in understanding how modern humans evolved. 
The excavation of the bones is shown in the picture above 
[Credit: Andrey Krivoshapkin]

Another find, dating to at least 35,000 years ago, was a tiny fragment of finger bone - a nail phalange.

'We struck really lucky this year,' he said. 'During works at Pleistocene levels of Strashnaya Cave we found new anthropological material. In levels dating to 35,000 to 40,000 years ago, we found a fragment of a human nail phalanx.

'Further down (in older layers) there was a fragment of a human skull and, even further, a fragment of a rib which we believe is human.'

He stated: 'Both the skull and the rib should be no younger than 50,000 years old.'

The discoveries have led to palpable excitement among scientists in Siberia.

The academic said that 'in an ideal world we would like to have the nail phalange to belong to a modern man, carrying genes of both Neanderthal and Denisovan man, and the older find (the skull) belonging to Neanderthal Man, and the oldest fragment - the rib - to be from Denisovan man.'

Archaeologists leading the excavation at Strashnaya cave say the skull is 
'no younger than 50,000-years-old' and may be even older 
[Credit: Andrey Krivoshapkin]

However, he cautioned: 'Right now, however these are just my fantasies.  As we know, analysis results might turn out to be completely unexpected. But whatever the results, they will help us understand the interaction of modern humans, Neanderthals and Denisovans in the Altai territory.'

It is the first discovery of man's remains at the cave for more than a quarter of a century. In 1989, archaeologists found human teeth dating to the Upper Paleolithic period, around 20,000 years ago. The skull fragment was found alongside 'labour tools' which match previously discovered implements confirmed as belong to Neanderthals, he said.

The cave stands on the left bank of the River Inya, some 2.5 km north of Tigiryok village in Altai region. Earlier excavations here found variety of Stone Age tools along with Bronze, Iron and Middle Ages pottery.

The cave is around 125 kilometres west of the more famous Denisova Cave which changed our understanding of the origins of man.

Denisova was home through many millennia to both Neanderthals and our modern human ancestors. It was here that, in 2008, a tiny finger bone fragment of so-called 'X woman' was discovered,  a young female who lived around 41,000 years ago, analysis of which indicated that she was genetically distinct from both Neanderthals and modern humans.

This previously unknown hominin species or subspecies - long extinct - was christened the Denisovans after the name of this cave. One conclusion from analysis of ancient bone fragments is that our own species, Homo sapiens, occasionally had assignations with both Neanderthals and Denisovans.

Source: The Siberian Times [August 14, 2015]

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Marks on 3.4-million-year-old bones not due to trampling, analysis confirms

Marks on two 3.4 million-year-old animal bones found at the site of Dikika, Ethiopia, were not caused by trampling, an extensive statistical analysis confirms. The Journal of Human Evolution is publishing the results of the study, which developed new methods of fieldwork and analysis for researchers exploring the origins of tool making and meat eating in our ancestors.

Detail of the marks on a fossilized rib bone, one of the two controversial bones. 
“The best match we have for the marks, using currently available data, would 
still be butchery with stone tools," says anthropologist Jessica Thompson 
[Credit: Zeresenay Alemseged]

"Our analysis clearly shows that the marks on these bones are not characteristic of trampling," says Jessica Thompson, an assistant professor of anthropology at Emory University and lead author of the study. "The best match we have for the marks, using currently available data, would still be butchery with stone tools."

The 12 marks on the two specimens -- a long bone from a creature the size of a medium antelope and a rib bone from an animal closer in size to a buffalo -- most closely resemble a combination of purposeful cutting and percussion marks, Thompson says. "When these bones were hit, they were hit with enormous force and multiple times."

The paper supports the original interpretation that the damage to the two bones is characteristic of stone tool butchery, published in Nature in 2010. That finding was sensational, since it potentially pushed back evidence for the use of stone tools, as well as the butchering of large animals, by about 800,000 years.

The Nature paper was followed in 2011 by a rebuttal in the Proceedings of the National Academy of Sciences (PNAS), suggesting that the bones were marked by incidental trampling in abrasive sediments. That sparked a series of debates about the significance of the discovery and whether the bones had been trampled.

For the current paper, Thompson and her co-authors examined the surfaces of a sample of more than 4000 other bones from the same deposits. They then used statistical methods to compare more than 450 marks found on those bones to experimental trampling marks and to the marks on the two controversial specimens.

"We would really like to understand what caused these marks," Thompson says. "One of the most important questions in human evolution is when did we start eating meat, since meat is considered a likely explanation for how we fed the evolution of our big brains."

Evidence shows that our genus, Homo, emerged around 2.8 million years ago. Until recently, the earliest known stone tools were 2.6 million years old. Changes had already been occurring in the organization of the brains of the human lineage, but after this time there was also an increase in overall brain size. This increased size has largely been attributed to a higher quality diet.

Anthropologist Jessica Thompson at work in the field in Africa. She specializes 
in the study of what happens to bones after an animal dies 
[Credit: Zeresenay Alemseged]

While some other apes are known to occasionally hunt and eat animals smaller than themselves, they do not hunt or eat larger animals that store abundant deposits of fat in the marrow of their long bones. A leading hypothesis in paleoanthropology is that a diet rich in animal protein combined with marrow fat provided the energy needed to fuel the larger human brain.

The animal bones in the Dikika site, however, have been reliably dated to long before Homo emerged. They are from the same sediments and only slightly older than the 3.3-million-year-old fossils unearthed from Dikika belonging to the hominid species Australopithecus afarensis.

Thompson specializes in the study of what happens to bones after an animal dies. "Fossil bones can tell you stories, if you know how to interpret them," she says.

A whole ecosystem of animals, insects, fungus and tree roots modify bones. Did they get buried quickly? Or were they exposed to the sun for a while? Were they gnawed by a rodent or chomped by a crocodile? Were they trampled on sandy soil or rocky ground? Or were they purposely cut, pounded or scraped with a tool of some kind?

One way that experimental archeologists learn to interpret marks on fossil bones is by modifying modern-day bones. They hit bones with hammer stones, feed them to carnivores and trample them on various substrates, then study the results.

Based on knowledge from such experiments, Thompson was one of three specialists who diagnosed the marks on the two bones from Dikika as butchery in a blind test, before being told the age of the fossils or their origin.

The PNAS rebuttal paper, however, also used experimental methods and came to the conclusion that the marks were characteristic of trampling.

Thompson realized that data from a larger sample of fossils were needed to chip away at the mystery.

"Fossil bones can tell you stories, if you know how to interpret them," Jessica Thompson 
says. For instance, the marks on this fossilized bone from the Dikika site are
 diagnostic of punctures made by crocodile teeth 
[Credit: Jessica Thompson]

The current paper investigated with microscopic scrutiny all non-hominin fossils collected from the Hadar Formation at Dikika. The researchers collected a random sample of fossils from the same deposits as the controversial specimens, as well as nearby deposits. They measured shapes and sizes of marks on the fossil bones. Then they compared the characteristics of the fossil marks statistically to the experimental marks reported in the PNAS rebuttal paper as being typical of trampling damage. They also investigated the angularity of sand grains at the site and found that they were rounded -- not the angular type that might produce striations on a trampled bone.

"The random population sample of the fossils provides context," Thompson says. "The marks on the two bones in question don't look like other marks common on the landscape. The marks are bigger, and they have different characteristics."

Trample marks tend to be shallow, sinuous or curvy. Purposeful cuts from a tool tend to be straight and create a narrow V-shaped groove, while a tooth tends to make a U-shaped groove. The study measured and quantified such damage to modern-day bones for comparison to the fossilized ones.

"Our analysis shows with statistical certainty that the marks on the two bones in question were not caused by trampling," Thompson says. "While there is abundant evidence that other bones at the site were damaged by trampling, these two bones are outliers. The marks on them still more closely resemble marks made by butchering."

One hypothesis is that butchering large animals with tools occurred during that time period, but that it was an exceedingly rare behavior. Another possibility is that more evidence is out there, but no one has been looking for it because they have not expected to find it at a time period this early.

The Dikika specimens represent a turning point in paleoanthropology, Thompson says. "If we want to understand when and how our ancestors started eating meat and moving into that ecological niche, we need to refine our search images for the field and apply these new recovery and analytical methods. We hope other researchers will use our work as a recipe to go out and systematically collect samples from other sites for comparison."

In addition to Dikika, other recent finds are shaking up long held views of hominin evolution and when typical human behaviors emerged. This year, a team led by archaeologist Sonia Harmand in Kenya reported unearthing stone tools that have been reliably dated to 3.3 million years ago, or 700,000 years older than the previous record.

"We know that simple stone tools are not unique to humans," Thompson says. "The making of more complex tools, designed for more complex uses, may be uniquely human."

Author: Carol Clark | Source: Emory Health Sciences [August 14, 2015]

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Apes may be closer to speaking than many scientists think

Koko the gorilla is best known for a lifelong study to teach her a silent form of communication, American Sign Language. But some of the simple sounds she has learned may change the perception that humans are the only primates with the capacity for speech.

Meet Koko, Gorilla Spokesperson [Credit: The Gorilla Foundation]

In 2010, Marcus Perlman started research work at The Gorilla Foundation, where Koko has spent more than 40 years living immersed with humans -- interacting for many hours each day with psychologist Penny Patterson and biologist Ron Cohn.

"I went there with the idea of studying Koko's gestures, but as I got into watching videos of her, I saw her performing all these amazing vocal behaviors," says Perlman, now a postdoctoral researcher in the lab of University of Wisconsin-Madison psychology Professor Gary Lupyan.

The vocal and breathing behaviors Koko had developed were not necessarily supposed to be possible.

"Decades ago, in the 1930s and '40s, a couple of husband-and-wife teams of psychologists tried to raise chimpanzees as much as possible like human children and teach them to speak. Their efforts were deemed a total failure," Perlman says. "Since then, there is an idea that apes are not able to voluntarily control their vocalizations or even their breathing."

Instead, the thinking went, the calls apes make pop out almost reflexively in response to their environment -- the appearance of a dangerous snake, for example.

And the particular vocal repertoire of each ape species was thought to be fixed. They didn't really have the ability to learn new vocal and breathing-related behaviors.

These limits fit a theory on the evolution of language, that the human ability to speak is entirely unique among the nonhuman primate species still around today.

"This idea says there's nothing that apes can do that is remotely similar to speech," Perlman says. "And, therefore, speech essentially evolved -- completely new -- along the human line since our last common ancestor with chimpanzees."

However, in a study published online in July in the journal Animal Cognition, Perlman and collaborator Nathaniel Clark of the University of California, Santa Cruz, sifted 71 hours of video of Koko interacting with Patterson and Cohn and others, and found repeated examples of Koko performing nine different, voluntary behaviors that required control over her vocalization and breathing. These were learned behaviors, not part of the typical gorilla repertoire.

Among other things, Perlman and Clark watched Koko blow a raspberry (or blow into her hand) when she wanted a treat, blow her nose into a tissue, play wind instruments, huff moisture onto a pair of glasses before wiping them with a cloth and mimic phone conversations by chattering wordlessly into a telephone cradled between her ear and the crook of an elbow.

"She doesn't produce a pretty, periodic sound when she performs these behaviors, like we do when we speak," Perlman says. "But she can control her larynx enough to produce a controlled grunting sound."

Koko can also cough on command -- not particularly groundbreaking human behavior, but impressive for a gorilla because it requires her to close off her larynx.

"The motivation for the behaviors varies," Perlman says. "She often looks like she plays her wind instruments for her own amusement, but she tends to do the cough at the request of Penny and Ron."

These behaviors are all learned, Perlman figures, and the result of living with humans since Koko was just six months old.

"Presumably, she is no more gifted than other gorillas," he says. "The difference is just her environmental circumstances. You obviously don't see things like this in wild populations."

This suggests that some of the evolutionary groundwork for the human ability to speak was in place at least by the time of our last common ancestor with gorillas, estimated to be around 10 million years ago.

"Koko bridges a gap," Perlman says. "She shows the potential under the right environmental conditions for apes to develop quite a bit of flexible control over their vocal tract. It's not as fine as human control, but it is certainly control."

Orangutans have also demonstrated some impressive vocal and breathing-related behavior, according to Perlman, indicating the whole great ape family may share the abilities Koko has learned to tap.

Author: Chris Barncard | Source: University of Wisconsin-Madison [August 14, 2015]

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