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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Humans responsible for demise of gigantic ancient mammals

Early humans were the dominant cause of the extinction of a variety of species of giant beasts, new research has revealed.

A glyptodon, a giant relation of the armadillo 
[Credit: WikiCommons]

Scientists at the universities of Exeter and Cambridge claim their research settles a prolonged debate over whether mankind or climate change was the dominant cause of the demise of massive creatures in the time of the sabretooth tiger, the woolly mammoth, the woolly rhino and the giant armadillo.

Known collectively as megafauna, most of the largest mammals ever to roam the earth were wiped out over the last 80,000 years, and were all extinct by 10,000 years ago.

Lewis Bartlett, of the University of Exeter, led the research, which also involved the universities of Reading and Bristol and is published in the journal Ecography. He said cutting-edge statistical analysis had helped solve the mystery almost beyond dispute, concluding that man was the dominant force in wiping out the creatures, although climate change could also have played a lesser role.

The researchers ran thousands of scenarios which mapped the windows of time in which each species is known to have become extinct, and humans are known to have arrived on different continents or islands. This was compared against climate reconstructions for the last 90,000 years.

Examining different regions of the world across these scenarios, they found coincidences of human spread and species extinction which illustrate that man was the main agent causing the demise, with climate change exacerbating the number of extinctions. However, in certain regions of the world – mainly in Asia – they found patterns which patterns were broadly unaccounted for by either of these two drivers, and called for renewed focus on these neglected areas for further study.

Lewis Bartlett, a researcher from the University of Exeter’s Centre for Ecology and Conservation, said: “As far as we are concerned, this research is the nail in the coffin of this 50-year debate - humans were the dominant cause of the extinction of megafauna. What we don’t know is what it was about these early settlers that caused this demise. Were they killing them for food, was it early use of fire or were they driven out of their habitats? Our analysis doesn’t differentiate, but we can say that it was caused by human activity more than by climate change. It debunks the myth of early humans living in harmony with nature.”

Dr Andrea Manica, of Cambridge University, was lead supervisor on the paper. He said: “Whilst our models explain very well the timing and extent of extinctions for most of the world, mainland Asia remains a mystery. According to the fossil record, that region suffered very low rates of extinctions. Understanding why megafauna in mainland Asia is so resilient is the next big question."

Source: University of Exeter [August 13, 2015]

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