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Some animals, including chimpanzees, crows, elephants, sea otters and dolphins, are known to use tools to extract food from their environment and for other functions. But what really sets people apart from tool-using animals is the uniquely human practice of using tools to make other tools, which researchers say requires another, more evolved level of intelligence.
But when was the first instance of humans or even pre-human species using tools to make tools? We can only speculate, but scientists working in Ethiopia have identified cut marks on fossilized animals bones buried in sediment from 3.4 million years ago—earlier than any other evidence of tool use found so far. This may mean that the ancestors of humans, a species called Australopithecus, were much more evolved intellectually than previously believed.
"To make a stone tool, you use a tool to make a second tool," Briana Pobiner, a paleoanthropologist with the U.S. Smithsonian Institution, told Live Science . "There's a lot of planning and forethought involved," Pobiner said. The creatures had to choose the correct type of rock and the correct striking tool and hold both in the correct position and then strike in an exact manner to flake off chips and make a new tool.
Pobiner was not involved in the recent study that examined the 3.4-million-year-old animal bones.
A model of an Australopithecus female (Photo by alberto-g-rovi/ Wikimedia Commons )
The researchers involved re-examined the bones, which some theorized were marked simply by trampling, Live Science says. The new research does not definitively prove that early hominins cut the bones with tools, but if it is true, then our earliest cousins were using bones 800,000 years earlier than previously known.
The theory that pre-human species cut the bones was put forward in 2010, but Live Science says at that time the earliest known evidence of tool use, from Gona, also in Ethiopia, went back only 2.6 million years. In May 2015, however, another team of researchers reported they'd found tools from 3.3 million years ago, in Kenya.
Skulls of 1. Gorilla 2. Australopithecine 3. Homo erectus 4. Neanderthal (La-Chapelle-au-Seine) 5. Steinheim Skull 6. Modern human (Image by Vladlen666/Wikimedia Commons)
The cuts marks on the animals bones, one from an antelope-sized creature and the other from a bison-sized creature, go back 100,000 years earlier than the tools from Kenya. The researchers simulated trampling of bones and compared them to the bones in question. The experimentally trampled bones appeared to have different types of marks than the bones from 3.4 million years ago.
“The bones were found several years ago in the history-rich sediments of Dikika, an area in the Awash River valley in Ethiopia,” says Live Science. “This arid region — part of the East African Rift valley, where two continental plates are peeling apart — has yielded some of the best examples of both early hominin fossils and fossils from anatomically modern early humans. At the time the bones were deposited, the region was a patchwork of swampy forest areas dotted with lakes, and a more open savanna where bigger animals roamed, said lead study author Jessica Thompson, an assistant professor of anthropology at Emory University in Georgia. The tree-swinging Australopithecus likely lived in the forested regions, Thompson said.”
Just a few hundred meters away from the bone site, scientists had previously found a hominin baby, an Australopithecus specimen, that they estimated dates back 3.3 million years.
Featured image: Featured image: Researchers said in 2010 these animal bones, found in sediment dated about 3.4 million years ago, had been deliberately cut, apparently by a creatures of a pre-human hominin species, Australopithecus. A new study seems to confirm their conclusion. (Photo by Dikika Research Project)
By Mark Miller
Human ancestors used tools far earlier than previously thought
THE ANCESTORS of early humans used stone tools to butcher animal carcasses nearly one million years earlier than previously thought.
Archaeologists revised the date after spotting distinctive cut and crush marks made by stone tools on animal bones dating to 3.4 million years ago.
The remains, including a rib from a cow-like creature and a thigh bone from an animal the size of a goat, were recovered from riverbed sediments in Dikika,northern Ethiopia, last January.
The marks show where stone tools were used to slice and scrape meat from the carcasses and where the bones were crushed to expose the marrow inside.
The discovery suggests meat was on the menu far back in our evolutionary history, and long before the arrival of the first human species, Homo habilis, 2.3 million years ago.
“We were just walking along when we discovered the two bones,” said Shannon McPherron, an archaeologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
“We picked up the rib fragment, flipped it over and there were these two, clear marks. Soon after, we found the second bone, also with a lot of marks on it.”
Until now, the oldest evidence of stone-tool use was a haul of more than 2,600 stone flakes estimated to be 2.5 million years old that was discovered in another part of Ethiopia in 1997. These tools had been shaped to make sharp cutting edges, but in Dikika, the stones were most likely used as they were found.
The butchered bones were discovered close to where the skeleton of a probable human ancestor, nicknamed Lucy, was found. Lucy belonged to a species called Australopithecus afarensisand lived in the region around 3.4 million years ago. At the time, the region was warm and wet, with patches of grassland and heavily forested areas populated with early forms of giraffes, monkeys, elephants and rhinos.
“Now, when we imagine Lucy walking around the east African landscape looking for food, we can for the first time imagine her with a stone tool in hand looking for meat,” said Dr McPherron.
Detailed analysis of the cut marks on the bones showed they differ substantially from tooth and claw marks. One of the marks was embedded with a small fragment of stone, according to a report in the journal, Nature.
The use of simple stone tools to remove meat and marrow marks a crucial moment in the human story. As the ancestors of early humans turned to meat for sustenance, they were able to grow larger brains which in turn enabled them to make more sophisticated tools.
“These bones may take us to the very beginning of that process,” said Chris Stringer, head of human origins at the Natural History Museum in London. “What we need from these sites now are evidence of the stone tools themselves, so we can see if they were manufactured or were natural.”
Lucy and others of her species probably carried natural stone tools around with them to use when they encountered a dead animal. “It’s not a trivial thing to leave the trees behind, wander out on to this open landscape and start removing flesh and marrow from a carcass. Those carcasses were attracting carnivores . . . so they were taking a major risk,” said Dr McPherron. – ( Guardianservice)
Answers at hand
Matthew Skinner at the University of Kent in the UK and his colleagues have now found something they think is as exciting as finding an earlier tool.
They decided to look at the hands that held them. Specifically, they looked at metacarpal bones – the five bones in the palm of the hand that articulate the fingers. Because the bone ends are made of soft, spongy bone tissue, they are shaped over a lifetime of use and moulded by what that hand has done.
A chimp, for instance, spends a lot of time swinging from branches and knuckle-walking. That exerts a great deal of force on the joints in its hands, in a specific way. Skinner and his colleagues predicted how this should shape the soft bone in ape hands, then looked at modern ape bones, finding their predictions were right.
Top row&colon a selection of metacarpal bones. Bottom row&colon CT scans of the same specimens, showing the structure inside (Image&colon T.L. Kivell)
Modern human metacarpals looked different because we use our hands differently. Most of our activities involve some kind of pinching – think of how you hold a pencil or pick up a cup. This precision squeeze between thumb and fingers is uniquely human and a legacy from our flint-wielding ancestors.
When Skinner and his colleagues looked at the metacarpals of early human species and neanderthals – who also used stone flakes for tasks like scraping and butchering – they found bone ends that were shaped like modern human bones, and unlike ape bones.
Finally, they looked at metacarpals from four Australopithecus africanus individuals, up to 3 million years old. This revealed that their owners had been tree swingers but had also spent a lot of energy tightly pinching small objects, suggesting they were indeed early tool users.
Both Alemseged and Shannon McPherron, an archaeologist from the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany, and lead author of the study, say that the next task is to return to the region and keep looking for evidence to tie up the story.
They hope to establish that it was in fact A. afarensis that used the tools, rather than any other species that has not yet been found in the region.
"It's always hard to associate a behaviour with a particular hominin," Dr McPherron explained to BBC News.
"We're never so lucky as to find a hominin dead with the archaeology in its hand."
But more than that, the team want to look for tools and any potential evidence of their manufacture, to find what kind of tools the A. afarensis butcher actually had.
The previous record-holders for oldest stone tools seemed relatively advanced, Dr McPherron explained, so experts have guessed for some time that less sophisticated tools would be found.
"What we can now think about is a fairly extended period of time when these hominins were experimenting with stone, perhaps using naturally occurring flakes," he said.
"But at some point they would've started to make their own. What we need to do is fill in that time period."
Chris Stringer of the Natural History Museum in London cautions against making firm conclusions about the development of tool use, given the limited number of artifacts from the current find.
"We have to be cautious that these are just a couple of bones with what seem to be cut marks on them one would like to have stone tools associated with them to really clinch the case," he told BBC News.
However, he agrees that pushing the first known date of tool use back by nearly a million years is, regardless, "a big story".
"It suggests that meat-eating and butchery behaviour is pre-human - it's an ancestral behaviour and as such it gives an interesting perspective on the Australopithecines that we didn't have before," he said.
"They seemed to be vegetarian and lacking significant aspects of human behaviour, and in a sense this would bring them somewhat closer to us."
Ancient humans used stone tools 3.4mn years ago: Scientists
Archaeologists have found that our ancient ancestors were using stone tools to butcher animals one complete million years earlier than previously thought.
London: In a discovery that may rewrite the
history of mankind, archaeologists have found that our ancient
ancestors were using stone tools to butcher animals one complete
million years earlier than previously thought.
It has been believed that the first use of tools is one
of the pivotal moments of humanity`s development some 2.5
million years ago.
But a team of archaeologists were stunned when they
found the marks of sharp stone blades on fossilised animals
bones believed to be over 3.4 million-year-old.
Dr Zeresenay Alemseged, from the California Academy of
Sciences who found the bones in Ethiopia, said they believe
the tools were used to carve slices of meat off the bones, and
smash them open to reach the nutritious marrow inside.
Dr Alemseged`s team made the latest discovery on a
fossilised bone unearthed in the Afar region of Ethiopia. The
bones were butchered by an squat ape-like ancestor called
The best known member of the species is "Lucy" -- who
was found in Ethiopia`s Awash Valley in 1974 and named after
the Beatles` song Lucy in the Sky with Diamonds. Lucy was
around 3ft 6inches and walked upright.
Dr Alemseged said: "The discovery dramatically shifts
the known time frame of a game-changing behaviour for our
"Tool use fundamentally altered the way our early
ancestors interacted with nature, allowing them to eat new
types of food and exploit new territories.
"It also led to tool making -- a critical step in our
evolutionary path that eventually enabled such advanced
technologies as airplanes, MRI machines and iPhones."
Until now, the oldest evidence of tools came from Bouri
in Ethiopia where cut-marked bones were dated to around 2.5
million years ago. The oldest known stone tools -- dated
to the same period -- were found close by.
According to the scientist, the new findings "will
definitely force us to revise our text books on human
evolution, since it pushes the evidence for tool use and meat
eating in our family back by nearly a million years."
"These developments had a huge impact on the story of
The discovery, reported in the journal Nature, is the
first evidence that Lucy and her relatives used tools.
Dr Shannon McPherron, of the Max Planck Institute in
Leipzig, Germany said: "Now, when we imagine Lucy walking
around the East African landscape looking for food, we can for
the first time imagine her with a stone tool in hand and
looking for meat.
"With stone tools in hand to quickly pull off the
flesh and break open bones animal carcasses would have become
a more attractive source of food.
"This type of behaviour sent us down a path that would
lead to two of the defining features of our species- carnivory
and tool manufacture and use."
Chip Clark, Smithsonian Institution Stone core and flake from Lokalalei, Kenya, about 2.3 million years old
Dawn of technology
Early humans in East Africa used hammerstones to strike stone cores and produce sharp flakes. For more than 2 million years, early humans used these tools to cut, pound, crush, and access new foods—including meat from large animals.
How Do We Know This Zebra Was Food?
Human Origins Program, Smithsonian Institution Scanning electron micrograph image of cut marks on fossil bone
Stone tool marks on this zebra bone look like those made during butchery experiments. Scientists have made experimental stone tools and used them to butcher modern animals. There is a strong similarity between the marks their tools made and the marks on fossil animal bones, indicating that early humans used stone tools to butcher animals by at least 2.6 million years ago.
Handaxes came in handy
Beginning 1.7 million years ago
Around this time, toolmakers began to strike huge flakes off stone cores. They shaped the large flakes into handaxes by striking smaller flakes all around the edges. These multipurpose tools dominated early human technology for more than a million years. Ancient handaxes have been found in Africa, Asia, and Europe. Learn more about them and other Early Stone Age tools.
Handaxe Makers Cope with Catastrophe
James Di Loreto, & Donald H. Hurlbert, Smithsonian Institution Handaxe from Bose, China, about 803,000 years old.
Smithsonian scientists and their Chinese colleagues found these handaxes in the same sediment layer with tektites, small rocks that formed during a meteor impact 803,000 years ago.
Since the handaxes and tektites were in the same layer, both are the same age. Early humans must have moved into the area right after the impact. They may have made the handaxes from rocks that were exposed when forests burned.
A huge meteor impact occurred in the atmosphere near China 803,000 years ago and the shock caused earth rocks to melt and explode, forming tektites. Widespread forest fires followed. Shortly after, humans moved into the barren landscape and scavenged for resources.
Control of fire provided a new tool with several uses—including cooking, which led to a fundamental change in the early human diet. Cooking released nutrients in foods and made them easier to digest. It also rid some plants of poisons.
The earliest hearths are at least 790,000 years old. Some researchers think cooking may reach back more than 1.5 million years.
Chip Clark, Smithsonian Institution Wooden thrusting spear, Schöningen, Germany, about 400,000 years old.
Hunting Large Animals
By at least 500,000 years ago, early humans were making wooden spears and using them to kill large animals.
Early humans butchered large animals as long as 2.6 million years ago. But they may have scavenged the kills from lions and other predators. The early humans who made this spear were hunting large animals, probably on a regular basis.
Reducing the risk
Hunting large animals was a risky business. Long spears like this one were thrust into an animal, enabling our ancestors to hunt from a somewhat safer distance than was possible with earlier weapons. Three wooden spears like the 400,000-year-old one illustrated here were found at Schöningen, Germany, along with stone tools and the butchered remains of more than 10 horses.
Oldest evidence of hunting
James Di Loreto, & Donald H. Hurlbert, Smithsonian Institution Horse shoulder blade or scapula from Boxgrove, England, about 500,000 years old
The semicircular wound on this fragment of a horse shoulder blade was made by a weapon such as a spear, indicating it was killed by early humans. Other horse bones from the same site have butchery marks from stone tools.
Explosion of technology
Eventually new kinds of tools replaced stone handaxes. Some were small or made of several parts. Some were made of bone, ivory, or antler. Over the past 100,000 years, as modern humans spread around the world, the pace of technological change accelerated—leading to today’s extraordinary diversity of specialized tools.
Chip Clark, Smithsonian Institution Bone needles from Xiaogushan, Liaoning Province, China, about 30,000–23,000 years old
Awls and perforators were probably invented in Africa and carried to colder climates, where they were used to pierce holes in clothing. Later, humans used bone and ivory needles to sew warm, closely fitted garments.
Carving and shaping
Burins are specialized stone flakes with sharp, chisel-like tips. Humans used them to work bone, antler, ivory, and wood and to carve designs and images on the surfaces of these materials.
More than 70,000 years ago, humans in Central Africa used some of the earliest barbed points to spear huge prehistoric catfish weighing as much as 68 kg (150 lbs.), enough to feed 80 people for two days. Later, humans used harpoons to hunt large, fast marine mammals.
Hunting fast and dangerous prey
Spear-throwers provided leverage for hurling spears and darts greater distances with more speed and accuracy and with less chance of injury from prey. Stone or bone points, attached to spears or darts, enabled humans to exploit fast-moving prey like birds and large, dangerous prey like mammoths.
Karen Carr Studios Humans began making pottery for storage purposes
Early humans may have made bags from skin long ago. By around 26,000 years ago, they were weaving plant fibers to make cords and perhaps baskets. About 20,000 years ago, in China, they began making pottery.
Chimps Make Tools, Too
Chimpanzees in Guinea used this stone anvil and hammerstone to crack open oil palm nuts, an energy-rich food. Nut cracking is one of the most sophisticated examples of chimpanzee tool use.(Specimen courtesy of Professor Tetsuro Matsuzawa, Kyoto University Primate Research Institute, Kyoto, Japan)
Chip Clark, Smithsonian Institution Chimpanzee stone anvil, hammerstone with palm nuts, ant-dipping tool, and spear
Researchers in Senegal observed a chimpanzee sharpen this stick and use it to spear bush babies sleeping inside tree hollows—the first time chimpanzees were observed using tools to hunt. (Specimen courtesy of Dr. Jill Pruetz, Iowa State University, Iowa)
Chimpanzees in Guinea use specially prepared sticks like this to “fish” for ants, a high-protein food. They make holes in the side of a nest, insert the stick, and pull it out—covered with ants. (Specimen courtesy of Dr. Kathelijne Koops and Dr. William McGrew, Cambridge University, England)
Benefits and Costs of Eating Meat
Karen Carr Illustrations of the benefits and costs of eating meat.
- Meat is a concentrated source of calories, protein, fat, and nutrients.
- Unlike many plants, most meat does not naturally contain toxic chemicals so it was a relatively safe food for early humans.
- Meat is more quickly digested than plants and does not require large guts, saving energy for the brain and other organs.
- Hunting and scavenging large animals is risky and less predictable than gathering plants.
- Dangerous animals competed with early humans to obtain meat.
- Meat spoils quickly and can contain tapeworms and other parasites.
How can you tell if a rock is actually an early stone tool? Watch this video to find out.
Lucy the Butcher? Tool Use Pushed Back 800,000 Years
Human ancestors sliced meat much earlier than thought, bones suggest.
Early human ancestors may have been using tools about 800,000 years earlier than thought, according to a new study based on newfound bone evidence—prehistoric leftovers linked to the famed "Lucy" fossil's species.
The discovery suggests, to at least one scientist, that tool use may extend as far back as five million years ago, to the last common ancestor of chimps and humans.
Found in East Africa, the two 3.4 million-year-old animal bones behind the new study appear to have been cut and crushed by stone tools wielded by the apelike human-ancestor species Australopithecus afarensis.
"You have all these images in museums and elsewhere showing Lucy walking through this East African landscape looking for food, and now we can put a stone tool in Lucy's hand," said study co-author Shannon McPherron, an archaeologist with the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The finding, to be published tomorrow in the journal Nature, could force a scientific rethink of how the brain sizes of our early ancestors were affected by meaty diets.
A. Afarenisis Only Likely Candidate
Excavated from a dusty ridge in Ethiopia's Afar Basin, the two butchered bones include a rib (pictured above) from an unidentified cow-size animal and a thighbone from a goat-size antelope. Cut marks suggest that stone tools were used to remove the flesh from the bones and to extract marrow.
It's unlikely that the marks were been made by any other hominids, or hominins—members of our ancestral lineage and close evolutionary relatives—except A. afarensis.
"In this part of the world, at this time period, the only [hominid] species found to this point has been afarensis," McPherron said.
A. afarensis probably did not use their tools for hunting, he added. More likely, the early human ancestors were scavengers who used stones to butcher animal carcasses they came across.
Previous "Earliest" Human Tools
Prior to the new discovery, the earliest direct proof of stone-tool creation and use among hominins dated to about 2.5 million years ago.
This younger evidence consists of marked bones and stone tools, which many paleoanthropologists think were left behind by Homo habilis, or "handy man," one of the earliest species of the human genus, Homo.
According to some scientists, the likely H. habilis tools are too well made to have been our evolutionary ancestors' first attempts at making tools.
"Scientists have been able to show that hominins [living around 2.5 to 2.6 million years ago] weren't just randomly going up to a cobble bed and selecting any kind of rock. . ," said David Braun, a Paleolithic archaeologist at the University of Cape Town in South Africa.
"They were selecting certain types of rocks that were particularly good for making stone tools," said Braun, who was not involved in the new tool study but who wrote an accompanying commentary for Nature.
Because of the relative sophistication of the previous "oldest tools" record holders, he said, "many scientists have suggested there must be something older."
But while the new findings suggest A. afarensis was using stone tools, there's no evidence the species was making them. It's possible that, like modern chimpanzees, Lucy and her ilk were using unaltered rocks.
Maybe, though, proof of A. afarensis toolmaking just hasn't been found yet. "My gut feeling says that we're going to find evidence of [tool] manufacture as well," study co-author McPherron said.
Brain-Tool Feedback Loop for Early Human Ancestors?
The new tool findings could challenge theories about the effects of meat consumption on hominin brain size.
Some scientists have speculated that meat eating, stone-tool manufacture, and large hominin brains are related in a kind of feedback cycle.
The idea is that the "increased nutrients of meat allow you to grow a larger brain, which allows you to come up with novel solutions to make better stone tools, which allow you to get more meat," McPherron said.
"But here we're looking at meat consumption long before we're seeing increases in brain size."
Tools Date Back to Dawn of Human Evolution?
The new tool findings are "a very important scientific discovery," said paleoanthropologist John Shea, who also was not involved in the study.
In addition to pushing back the advent of hominin tool use by almost one million years, the study opens up the possibility that human-ancestral tool use is even older—perhaps dating all the way back to when the ancestors of humans and chimpanzees split about five million years ago, said Shea, of Stony Brook University in New York State. (Related: "'Key' Human Ancestor Found: Fossils Link Apes, First Humans?")
"Humans and chimpanzees both habitually use tools, so it stands to reason that the last common ancestor was a tool user as well," he added.
Tool Use Passed Down Along Evolutionary Lines?
Another possibility raised by the new discovery is that tool use was a learned behavior, passed down among hominins, across different species and even genera—for example, from Australopithecus to Homo.
"We'll have to find more than these two bones, but if we fill in the record and we find more evidence of this, then we might be looking at a kind of learned behavior that was then shared and passed along in and amongst these groups," study co-author McPherron said.
An alternative explanation, Stony Brook's Shea said, is that different hominin groups discovered stone-tool use, and later stone-tool manufacture, independently.
"It's not that complex a behavior," Shea said. Tool use probably arose "again and again until it was locked in as a stable component amongst later hominins."
2.) Stone handaxe (Acheulean tools): 1.6 million years ago
An Acheulean handaxe from Swakscombe, Kent, now held in the collections of the British Museum.
CM Dixon/Print Collector/Getty Images
The next leap forward in tool technology occurred when early humans began striking flakes off longer rock cores to shape them into thinner, less rounded implements, including a new kind of tool called a handaxe. With two curved, flaked surfaces forming the cutting edge (a technique known as bifacial working), these more sophisticated Acheulean tools proved sharper and more effective.
Named for St. Acheul on the Somme River in France, where the first tools from this tradition were found in the mid-19th century, Acheulean tools spread from Africa over much of the world with the migration of Homo erectus, a closer relative to modern humans. They have been found at sites as far afield as southern Africa, northern Europe and the Indian subcontinent.
In Lucy's hands
The only hominin species known from the Dikika region at that time was Australopithecus afarensis, the species represented by the famed "Lucy" fossil, and one that is hypothesised to be a direct ancestor of Homo and therefore of us.
But Lucy and her contemporaries were thought to be vegetarians, and many had assumed that tool use arose only in later, Homo species.
Study co-author Zeresenay Alemseged, the palaeoanthropologist from the California Academy of Sciences in San Francisco who leads a large research effort in the region, said that the find overturns much of what was thought about A. afarensis.
"For 30 years, no-one has been able to put stone tools in their hands, and we've done that for the first time," he told BBC News.
"We are showing for the first time that stone tool use is not unique to Homo or Homo-related species - we have A. afarensis now behaving like Homo in a way both by using tools and eating meat. It's another attribute that could enable us to link A. afarensis to the genus Homo."
The conclusions, however, are based on a small number of bones, and the inference of stone tool use is made indirectly: no tools were actually found at the site. That means it remains unclear if A. afarensis actually made the tools from larger bits of stone, or simply used sharpened fragments that were found.
Oldest evidence of stone tool use and meat-eating among human ancestors discovered: Lucy's species butchered meat
The evolutionary stories of the Swiss Army Knife and the Big Mac just got a lot longer. An international team of scientists led by Dr. Zeresenay Alemseged from the California Academy of Sciences has discovered evidence that human ancestors were using stone tools and consuming meat from large mammals nearly a million years earlier than previously documented. While working in the Afar Region of Ethiopia, Alemseged's "Dikika Research Project" team found fossilized bones bearing unambiguous evidence of stone tool use -- cut marks inflicted while carving meat off the bone and percussion marks created while breaking the bones open to extract marrow.
The bones date to roughly 3.4 million years ago and provide the first evidence that Lucy's species, Australopithecus afarensis, used stone tools and consumed meat. The research is reported in the August 12 issue of the journal Nature.
"This discovery dramatically shifts the known timeframe of a game-changing behavior for our ancestors," says Alemseged, Curator of Anthropology at the California Academy of Sciences. "Tool use fundamentally altered the way our early ancestors interacted with nature, allowing them to eat new types of food and exploit new territories. It also led to tool making -- a critical step in our evolutionary path that eventually enabled such advanced technologies as airplanes, MRI machines, and iPhones."
Although the butchered bones may not look like particularly noteworthy fossils to the lay person, Alemseged can hardly contain his excitement when he describes them. "This find will definitely force us to revise our text books on human evolution, since it pushes the evidence for tool use and meat eating in our family back by nearly a million years," he explains. "These developments had a huge impact on the story of humanity."
Until now, the oldest known evidence of butchering with stone tools came from Bouri, Ethiopia, where several cut-marked bones were dated to about 2.5 million years ago. The oldest known stone tools, dated to around the same time, were found at nearby Gona, Ethiopia. Although no hominin fossils were found in direct association with the Gona tools or the Bouri bones, an upper jaw from an early Homo species dated to about 2.4 million years ago was found at nearby Hadar, and most paleoanthropologists believe the tools were made and used only by members of the genus Homo.
The new stone-tool-marked fossil animal bones from Dikika have been dated to approximately 3.4 million years ago and were found just 200 meters away from the site where Alemseged's team discovered "Selam" in 2000. Dubbed "Lucy's Daughter" by the international press, Selam was a young Australopithecus afarensis girl who lived about 3.3 million years ago and represents the most complete skeleton of a human ancestor discovered to date.
"After a decade of studying Selam's remains and searching for additional clues about her life, we can now add a significant new detail to her story," Alemseged notes. "In light of these new finds, it is very likely that Selam carried stone flakes and helped members of her family as they butchered animal remains."
The location and age of the butchered bones from Dikika clearly indicate that a member of the A. afarensis species inflicted the cut marks, since no other hominin lived in this part of Africa at this time. These fossils provide the first direct evidence that this species, which includes such famous individuals as Lucy and Selam, used stone tools.
"Now, when we imagine Lucy walking around the east African landscape looking for food, we can for the first time imagine her with a stone tool in hand and looking for meat," says Dr. Shannon McPherron, archeologist with the Dikika Research Project and research scientist at the Max Planck Institute for Evolutionary Anthropology in Leipzig. "With stone tools in hand to quickly pull off flesh and break open bones, animal carcasses would have become a more attractive source of food. This type of behavior sent us down a path that later would lead to two of the defining features of our species -- carnivory and tool manufacture and use."
To determine the age of the butchered bones, project geologist Dr. Jonathan Wynn relied on a very well documented and dated set of volcanic deposits in the Dikika area. These same deposits were previously used to determine Selam's age, and they are well known from nearby Hadar, where Lucy was found. The cut-marked bones at Dikika were sandwiched between volcanic deposits that have been securely dated to 3. 24 and 3.42 million years ago, and they were located much closer to the older sediment. "We can very securely say that the bones were marked by stone tools between 3.42 and 3.24 million years ago, and that within this range, the date is most likely 3.4 million years ago," says Wynn, a geologist at the University of South Florida.
Both of the cut-marked bones discovered at Dikika came from mammals -- one is a rib fragment from a cow-sized mammal, and the other is a femur shaft fragment from a goat-sized mammal. Both bones are marred by cut, scrape, and percussion marks. Microscope and elemental analysis using secondary electron imaging and energy dispersive x-ray spectrometry demonstrated that these marks were created before the bones fossilized, meaning that recent damage can be eliminated as the cause of the marks. Additionally, the marks were consistent with the morphology of stone-inflicted cuts rather than tooth-inflicted marks. Dr. Hamdallah Bearat from the Ira A. Fulton Schools of Engineering at Arizona State University determined that one cut-mark even contained a tiny, embedded piece of rock that was likely left behind during the butchering process.
"Most of the marks have features that indicate without doubt that they were inflicted by stone tools," explains Dr. Curtis Marean from the Institute of Human Origins at Arizona State University, who helped with the mark identifications. "The range of actions that created the marks includes cutting and scraping for the removal of flesh, and percussion on the femur for breaking it to access marrow."
While it is clear that the Australopithecines at Dikika were using sharp-edged stones to carve meat from bones, it is impossible to tell from the marks alone whether they were making their tools or simply finding and using naturally sharp rocks. So far, the research team has not found any flaked stone tools at Dikika from this early time period. This could indicate that the Dikika residents were simply opportunistic about finding and using sharp-edged stones. However, the sedimentary environment at the site suggests another potential explanation.
"For the most part, the only stones we see coming from these ancient sediments at Dikika are pebbles too small for making tools," says McPherron. "The hominins at this site probably carried their stone tools with them from better raw material sources elsewhere. One of our goals is to go back and see if we can find these locations, and look for evidence that at this early date they were actually making, not just using, stone tools."
Regardless of whether or not Selam and her relatives were making their own tools, the fact that they were using them to access nutritious meat and marrow from large mammals would have had wide-ranging implications for A. afarensis both physically and behaviorally.
"We now have a greater understanding of the selective forces that were responsible for shaping the early phases of human history," says Alemseged. "Once our ancestors started using stone tools to help them scavenge from large carcasses, they opened themselves up to risky competition with other carnivores, which would likely have required them to engage in an unprecedented level of teamwork."
While many questions remain about the history of tool use, tool making, and related dietary changes among human ancestors, this discovery adds a rich new chapter to the story -- a story that is deeply relevant to what makes us unique as a species.