Bastian
The Living Force
Hello.
This year, I have little time to read the American SOTT, so this may have been already published.
Published : March 28th 2019
Author : Richard Kemeny is a British freelance science journalist based in São Paulo, Brazil.
Also this other (older) article from the same site may be interesting (NB: of course, evolutionnist narrative...) :
Published : February 23th 2016
Author : Briana Pobiner is a paleoanthropologist at the Smithsonian’s Human Origins Program.
This year, I have little time to read the American SOTT, so this may have been already published.
Published : March 28th 2019
Author : Richard Kemeny is a British freelance science journalist based in São Paulo, Brazil.
Sapiens.org said:Fat, Not Meat, May Have Led to Bigger Hominin Brains
A new theory challenges assumptions about when and how our ancestors altered their behaviors to boost brainpower.
Northern Ethiopia was once home to a vast, ancient lake. Saber-toothed cats prowled around it, giant crocodiles swam within. The streams and rivers that fed it—over 3 million years ago, during the Pliocene—left behind trails of sediment that have now hardened into sandstone.
Deposited within these layers are fossils: some of early hominins, along with the bones of hippos, antelope, and elephants. Anthropologist Jessica Thompson encountered two of these specimens, from an area named Dikika, in 2010.
At the time, she was a visiting researcher at the Institute of Human Origins at Arizona State University. Given no explanation as to their history, she analyzed the bones and found signs of butchery. Percussion marks suggested someone may have accessed the marrow; cut marks hinted that flesh was stripped from bone. To her surprise, the specimens were 3.4 million years old, putting the butcher’s behaviors back 800,000 years earlier than conventional estimates would suggest. That fact got Thompson, now an assistant professor in the department of anthropology at Yale University, thinking there might be more traces of tool use from those early times.
In a wide-ranging review published in February’s issue of Current Anthropology, Thompson joins a team of researchers to weave together several strands of recent evidence and propose a new theory about the transition to large animal consumption by our ancestors. The prevailing view, supported by a confluence of fossil evidence from sites in Ethiopia, is that the emergence of flaked tool use and meat consumption led to the cerebral expansion that kickstarted human evolution more than 2 million years ago. Thompson and her colleagues disagree: Rather than using sharpened stones to hunt and scrape meat from animals, they suggest, earlier hominins may have first bashed bones to harvest fatty nutrients from marrow and brains.
Humans are the only primate to regularly consume animals larger than themselves. This nutritional exploitation, something Thompson and her colleagues call the “human predatory pattern,” has long been synonymous with the flesh-eating, man-the-hunter view of human origins.
Because large animals such as antelope pack a serious micro-and-macro-nutrient punch, scientists have thought their meat contributed to humanity’s outsized brains. A consensus arose in the 1950s that our ancestors first hunted small animals before moving on to larger beasts around 2.6 million years ago. Flaked tool use and meat eating became defining characteristics of the Homo genus.
“It’s a very appealing story,” says Thompson. “Right around that time there appeared to be the first stone tools and butchery marks. You have the origins of our Homo genus. A lot of people like to associate that with what it means to be human.”
Then, starting in the mid-1980s, an opposing theory arose in which Homo’s emergence wasn’t so tightly coupled with the origins of hunting and predatory dominance. Rather, early hominins first accessed brain-feeding nutrients through scavenging large animal carcasses. The debate has rolled on through the decades, with evidence for the scavenging theory gradually building.
The new paper goes further: Harvesting outer-bone meat would have come at significant costs, the authors argue. The chance of encountering predators is high when scraping raw flesh from a carcass. Chewing raw meat without specialized teeth doesn’t give much energetic benefit, studies have shown. In addition, meat exposed to the elements will quickly rot.
Marrow and brains, meanwhile, are locked inside bones and stay fresh longer. These highly nutritional parts are also a precursor to the fatty acids involved with brain and eye development. And more easily than flesh-meat, bones could be carried away from carcass sites, safe from predators.
Conventional thinking has been that the behavioral package of early hominins was to go after meat and marrow together, explains Briana Pobiner, a paleoanthropologist at the Smithsonian Institution, who did not contribute to the new paper. But in the new paper, she says, “This team has shown that marrow may have in fact been more important. It’s a nuance, but an important nuance.”
he Pliocene—between 5.3 and 2.6 million years ago—was an era of dramatic change. An intensely variable and cooling climate transformed vast swaths of rainforest into mosaics of grassland and savanna. Large clearings spawned ecological niches for opportunistic and versatile hominins like Australopithecus, a likely contender for the Homo ancestor, and Kenyanthropus to fill in. Larger predators may well have left carcasses for them to scavenge.
Evidence suggests hominins shifted their diet around 3.76 million years ago as they took advantage of the open spaces. By around 3.5 million years ago, some species of Australopithecus already showed increased brain sizes, up to 30 percent larger than chimpanzees of comparable body size. Canines had shrunk to proportions later seen in the genus Homo, and hand morphology was already more human than ape, with potential both for terrestrial travel and tool use.
Percussive tools, the authors argue, were the key to the transition to large animal exploitation. Rocks could bash open bones, exposing the marrow inside. The alternative—that humans sharpened stone against stone, creating a flaked tool to carve meat from bone—seems more onerous, they say. They argue that such meat carving and the associated tool creation would likely come later.
As to who wielded these percussive instruments, the timeline presents a puzzle. The earliest Homo specimen is now dated to 2.8 million years. The Dikika fossils suggest butchery behaviors at 3.4 million years ago. Homo may have emerged earlier than scientists suspected—a theory that would need more fossil evidence to support it—or another hominin, such as Australopithecus, may have created tools before Homo.
Some scholars aren’t convinced by the study’s arguments, however. For example, Craig Stanford, an anthropologist at the University of Southern California, questions the emphasis on hominin scavenging behavior appearing before hunting. “We have no examples today of animals that scavenge but don’t hunt,” he adds.
To test the new theory, the review authors suggest seeking out further evidence of percussive tools that predate flaked tools. Researchers could, they note, broaden the search for the signatures of such instruments within both the existing fossil record and at dig sites. Thompson’s graduate students, for example, are using 3D scanning and artificial intelligence techniques to improve the identification of marks on fossils—whether they were created by early hominins, saber-toothed cats, hyenas, or other types of creatures.
What they uncover could deal a blow to their theory, but it will also, undoubtedly, enrich our understanding of how our ancestors evolved.
Also this other (older) article from the same site may be interesting (NB: of course, evolutionnist narrative...) :
Published : February 23th 2016
Author : Briana Pobiner is a paleoanthropologist at the Smithsonian’s Human Origins Program.
Sapiens.org said:The First Butchers
Were there other toolmakers and meat eaters in our family tree?
Living humans, all 7.3 billion of us, are classified as Homo sapiens. That means we are all part of the same species; our genus is Homo, meaning “man,” and our species is sapiens, meaning “wise.” Both genetic and fossil evidence place the origin of our species at about 200,000 years ago in Africa. But when and where did the earliest members of the genus Homo evolve? And what makes our genus unique compared with other branches on our family tree?
The best candidate, based on current evidence, for the earliest species in our genus is Homo habilis (meaning “handy man”). This species, which was named from fossils found at Olduvai Gorge, in Tanzania, by a research team led by Louis Leakey, was announced in 1964. The team defined the new species based on the specific anatomy of the fossils, including a larger brain and body and smaller teeth than members of the earlier-known genus Australopithecus. But they also did something novel as far as naming a species goes—they linked Homo habilis with the origin of a specific behavior by suggesting that this species was the maker of the simple Oldowan stone tools found previously in the same sedimentary layer. (These tools—which are basically simple stone knives—are made when roundish rocks, called hammerstones, are struck against more angular rocks, called cores, to strike off sharp flakes.) Later, in 1981, when cut marks were found on animal fossils at Olduvai Gorge, they were presumed to have been created by Homo habilis wielding these stone tools to butcher large animals. Homo habilis was declared the toolmaker and the meat eater, and, as a result, a core part of the definition of our genus involved these two novel behaviors.
This narrative held for over three decades, through the late 1990s. In 1997, even earlier stone tools—dating to 2.5–2.6 million years old—were reported from the Gona study area in Ethiopia. In the same year, a new Homo habilis fossil upper-jaw fragment from the Hadar site in Ethiopia pushed the origin of this species back to 2.34 million years ago. Then, in 1999, 2.5-million-year-old stone-tool cut marks on animal fossils were reported from the Bouri site in Ethiopia, along with percussion marks made on bones when early humans smashed them open with stones to retrieve the nutritious marrow inside. Even with this new evidence, though, the correlation persisted, and this package of new traits—larger brains, stone toolmaking, and meat eating—still seemed to emerge in our earliest Homo ancestors around 2.3–2.5 million years ago.
But recent finds contradict those links. In 2010, a startling announcement was made: Two bones with stone-tool butchery marks dated to 3.4 million years ago had been found at the Dikika site in Ethiopia, pushing the earliest traces of meat eating nearly a million years earlier than previously known. This was also far earlier than the earliest Homo fossils. Did this mean Australopithecus could use, and maybe even make, stone tools?
Among other things, critics noted that no stone tools had been found at Dikika. So perhaps Australopithecus wasn’t actually making tools, but just picking up naturally sharp rocks to use as stone knives. However, in May 2015, 3.3-million-year-old stone tools from the Lomekwi 3 site, in Kenya, were announced, pushing back the origin of stone toolmaking by 700,000 years. Just two months earlier, in March 2015, a 2.8-million-year-old fossil mandible and teeth from the Ledi-Geraru research area, in Ethiopia, had pushed the origin of our genus back about 500,000 years. These fossils have not been assigned to a particular species of early Homo, but it is now well accepted that they are the earliest fossils of our genus.
The current evidence points to toolmaking and meat eating occurring by 3.3 million years ago, but only a handful of sites with stone tools and/or butchered animal bones have been found before about 1.8 million years ago. The earliest site with evidence that early humans repeatedly returned to one place to make stone tools and butcher animals, a site in Kenya known as Kanjera South, is dated to 2.0 million years ago; this seems to be the beginning of consistent butchery activities.
So now the evidence for making and using tools dates back to half a million years before the origin of our genus. Making tools almost certainly helped toolmakers survive. Toolmaking would have facilitated access to a wider range of foods and the ability to process those foods more intensively or efficiently, likely making them more palatable and yielding more calories. In the case of meat and marrow eating, toolmaking would have opened up new sources of food higher in protein, fat, and calories than many other foods available in African savanna landscapes.
Given these benefits, could stone toolmaking be a behavior more common in our evolutionary history than we thought, and not something that only emerged with our genus? Chimpanzees use stone tools to crack open nuts and even make wooden spears to hunt smaller primates called bush babies, suggesting that the capacity to make and use tools is rooted deep in our evolutionary history. Still, chimpanzees don’t use tools to make other tools, as early humans did when they created the first stone knives. They also don’t eat animals larger than themselves; their favorite prey are colobus monkeys, which are much smaller than they are. The earliest butchery marks are on the bones of extinct animals that were similar to today’s wildebeests and zebras, which were much bigger than the Australopithecus individuals having them for dinner.
So what does all this tell us about the idea that Homo was the first maker of stone tools?
Scientists construct hypotheses based on available evidence and then test those hypotheses by gathering additional evidence. The long-standing hypothesis that only our genus was capable of making and/or using stone tools to butcher large animals seems to have been refuted by the recent finds of stone tools at Lomekwi and butchered bones at Dikika—at least for now—since the oldest Homo fossils are half a million years younger than the tools and butchered bones. Perhaps continued field research in sediments dating to around 3.0–3.5 million years ago will turn up Homo fossils, and then the hypothesis will again be supported. (The absence of Homo fossils from this time period is not necessarily evidence of their absence.)
Bernard Wood of George Washington University says that “a convincing hypothesis for the origin of Homo remains elusive,” and argues that Homo habilis should be classified neither as Homo or Australopithecus, but in its own genus. A recent review of the evolution of early Homo suggests that anatomical, physiological, and behavioral traits long held to define our genus did not arise in a single integrated package, but instead emerged over about a million years in three distinct lineages, with some traits evolving earlier and some later. In any case, it has become clear with more evidence that the origin of our genus remains murky, and that Homo may not have been the earliest toolmaker and meat eater in our family tree.
