Found in a hilltop cave, the oldest known Homo erectus and Paranthropus robustus fossils shed light on a critical period of hominin evolution.

n the winter of 2015, Jesse Martin and Angeline Leece were extracting what they thought were baboon remains from a piece of rock. The two students at La Trobe University in Australia were part of an expedition to collect and study fossils from the Drimolen quarry northwest of Johannesburg, South Africa. As they cleaned the skull fragments and pieced them back together, however, they realized the fossils did not come from a baboon, but instead comprised the braincase of a young Homo erectus, a species never before identified in South Africa.

“I don’t think our supervisors believed us until they came over to have a look,” Martin recalls.

The braincase was described in the journal Science today, together with the skullcap of another ancient hominin, Paranthropus robustus, found at the same site. A suite of different dating techniques all hinted that the two species’ braincases were more or less the same age—about two million years old. This would make them the earliest fossils ever found for their respective species, according to the new study coauthored by Martin and Leece.

“I think they have made a strong case for the oldest Homo erectus in Africa, and in fact, in the world,” Lee Berger, a paleoanthropologist at the University of Witwatersrand, says in an email. A National Geographic Society explorer-at-large, Berger was not involved in the new study.

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Opinion: The Uncomfortable Limits of Human Knowledge

Science seems under assault. Attacks come from many directions, ranging from the political realm to groups and individuals masquerading as scientific entities. There is even a real risk that scientific fact will eventually be reduced to just another opinion, even when those facts describe natural phenomena—the very purpose for which science was developed. Hastening this erosion are hyperbolic claims of “truth” that science is often perceived to make and that practicing researchers may themselves project, whether intentionally or not.

I’m a researcher, and I get it. It seems difficult to explain the persistent success of scientific theories at describing nature, not to mention the constant march of technological advancement, without assigning at least some special epistemic status to those theories. I explore this challenge in my book, What Science Is and How It Really Works. If the history of science teaches us anything, it is that the ability of a theory to predict unobserved phenomena and lead to amazing new technologies is no proof that said theory is “true.”

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Worth reading article by Ed Yong in Atlantis.

In 1978, in a cave called Apidima at the southern end of Greece, a group of anthropologists found a pair of human-like skulls. One had a face, but was badly distorted; the other was just the left half of a braincase. Researchers guessed that they might be Neanderthals, or perhaps another ancient hominin. And since they were entombed together, in a block of stone no bigger than a microwave, “it was always assumed that they were the same [species] and came from the same time period,” says Katerina Harvati from Eberhard Karls University of Tübingen.

That’s wrong. By thoroughly analyzing both skulls using modern techniques, Harvati and her colleagues have shown that they are very different, in both age and identity.

The one with the face, known as Apidima 2, is a 170,000-year-old Neanderthal—no surprises there. But the other, Apidima 1, was one of us—a 210,000-year-old modern human. And if the team is right about that, the partial skull is the oldest specimen of Homo sapiens outside Africa, handily beating the previous record holder, a jawbone from Israel’s Misliya Cave that’s about 180,000 years old. “I couldn’t believe it at first,” Harvati says, “but all the analyses we conducted gave the same result.”

Until now, most researchers have focused on the more complete (but less interesting) of the two skulls. “Apidima 1 has just been ignored,” says Harvati. But its antiquity matters for three reasons. First, it pushes back the known presence of modern humans outside Africa by some 30,000 years. Second, it’s considerably older than all other Homo sapiens fossils from Europe, all of which are 40,000 years old or younger. Third, it’s older than the Neanderthal skull next to it.

Collectively, these traits mess up the standard story of Neanderthal and modern-human evolution. According to that narrative, Neanderthals slowly evolved in Europe, largely isolated from other kinds of hominins. When modern humans expanded out of Africa, their movements into Europe might have been stalled by the presence of the already successful Neanderthals. That explains why Homo sapiens stuck to a more southerly route into Asia, and why they left no European fossils until about 40,000 years ago. “The idea of Europe as ‘fortress Neanderthal’ has been gaining ground,” says Rebecca Wragg Sykes, an archaeologist from the University of Bordeaux, but identifying a 210,000-year-old Homo sapiens skull from Europe “really undermines that.”

“It suggests that early Homo sapiens groups got farther than we may have previously thought, occasionally occupying territories that later became that of Neanderthals,” adds Shara Bailey, an anthropologist at NYU. “Findings like this are very important for informing us on the evolution of our species.”

Read: Scientists have found the oldest known human fossils

The identity of Apidima 1 could also cast doubt on other archaeological finds from Europe, such as stone tools with no accompanying fossils. Researchers had long assumed that within a certain time window, “any archaeology was all the work of Neanderthals,” says Wragg Sykes. But if modern humans also occupied this “safe range,” which species actually created those artifacts?

These interpretations depend on the dating of the Apidima skulls, which has always been difficult. They were found in an odd place—a small niche near the cave ceiling, separated from any sediments that could have been easily dated. They were also entombed in breccia, a composite rock made from fragments that have been cemented together. It seems that, as ice ages came and went and sea levels rose and fell, parts of the cave’s interior were flooded and eroded, and both skulls were dislodged from their original resting places. They fell into a cavity and got stuck.

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Fascinating article by Daniel Yan in Aeon on how our brain see the things based upon our preformed expectations. f.sheikh 

The Book of Days (1864) by the Scottish author Robert Chambers reports a curious legal case: in 1457 in the town of Lavegny, a sow and her piglets were charged and tried for the murder of a partially eaten small child. After much deliberation, the court condemned the sow to death for her part in the act, but acquitted the naive piglets who were too young to appreciate the gravity of their crimes.

Subjecting a pig to a criminal trial seems perverse through modern eyes, since many of us believe that humans possess an awareness of actions and outcomes that separates us from other animals. While a grazing pig might not know what it is chewing, human beings are surely abreast of their actions and alert to their unfolding consequences. However, while our identities and our societies are built on this assumption of insight, psychology and neuroscience are beginning to reveal how difficult it is for our brains to monitor even our simplest interactions with the physical and social world. In the face of these obstacles, our brains rely on predictive mechanisms that align our experience with our expectations. While such alignments are often useful, they can cause our experiences to depart from objective reality – reducing the clear-cut insight that supposedly separates us from the Lavegny pigs.

One challenge that our brains face in monitoring our actions is the inherently ambiguous information they receive. We experience the world outside our heads through the veil of our sensory systems: the peripheral organs and nervous tissues that pick up and process different physical signals, such as light that hits the eyes or pressure on the skin. Though these circuits are remarkably complex, the sensory wetware of our brain possesses the weaknesses common to many biological systems: the wiring is not perfect, transmission is leaky, and the system is plagued by noise – much like how the crackle of a poorly tuned radio masks the real transmission.

But noise is not the only obstacle. Even if these circuits transmitted with perfect fidelity, our perceptual experience would still be incomplete. This is because the veil of our sensory apparatus picks up only the ‘shadows’ of objects in the outside world. To illustrate this, think about how our visual system works. When we look out on the world around us, we sample spatial patterns of light that bounce off different objects and land on the flat surface of the eye. This two-dimensional map of the world is preserved throughout the earliest parts of the visual brain, and forms the basis of what we see. But while this process is impressive, it leaves observers with the challenge of reconstructing the real three-dimensional world from the two-dimensional shadow that has been cast on its sensory surface.

Thinking about our own experience, it seems like this challenge isn’t too hard to solve. Most of us see the world in 3D. For example, when you look at your own hand, a particular 2D sensory shadow is cast on your eyes, and your brain successfully constructs a 3D image of a hand-shaped block of skin, flesh and bone. However, reconstructing a 3D object from a 2D shadow is what engineers call an ‘ill-posed problem’ – basically impossible to solve from the sampled data alone. This is because infinitely many different objects all cast the same shadow as the real hand. How does your brain pick out the right interpretation from all the possible contenders?

The second challenge we face in effectively monitoring our actions is the problem of pace. Our sensory systems have to depict a rapid and continuous flow of incoming information. Rapidly perceiving these dynamic changes is important even for the simplest of movements: we will likely end up wearing our morning coffee if we can’t precisely anticipate when the cup will reach our lips. But, once again, the imperfect biological machinery we use to detect and transmit sensory signals makes it very difficult for our brains to quickly generate an accurate picture of what we’re doing. And time is not cheap: while it takes only a fraction of a second for signals to get from the eye to the brain, and fractions more to use this information to guide an ongoing action, these fractions can be the difference between a dry shirt and a wet one.

Psychologists and neuroscientists have long wondered what strategies our brains might use to overcome the problems of ambiguity and pace. There is a growing appreciation that both challenges could be overcome using prediction. The key idea here is that observers do not simply rely on the current input coming in to their sensory systems, but combine it with ‘top-down’ expectations about what the world contains.