Despite more than half a century of hominin fossil discoveries in eastern Africa, the regional environmental context of the evolution and dispersal of modern humans and their ancestors is not well established. Particularly for the Pleistocene (or Ice Age) between 2,580,000 to 11,700 years ago, there are no continuous high-resolution paleo-environmental records available for the African continent.

The research team extracted two continuous 280-metre sediment cores from the Chew Bahir Basin in southern Ethiopia, an area where early humans lived and developed during the Pleistocene. Chew Bahir is very remotely situated in a deep tectonic basement in close vicinity to the Turkana area and the Omo-Kibish, key paleo-anthropological and archaeological sites. The cores yielded the most complete record for such a long period ever extracted in the area, revealing how different climates influenced the biological and cultural transformation of humans inhabiting the region.

An interdisciplinary team including geoscientists, sedimentologists, micro-paleontologists, geologists, geographers, geochemists, archaeologists, chronologists, and climate modellers worked towards recovering the two continuous sediment cores, from which so-called proxies (like microfossils or elemental variations) were used to glean data to reconstruct the region’s climate history. Archaeologists, evolutionary biologists, and evolutionary anthropologists then identified phases of climatic stress as well as more favourable conditions and interpreted how these factors changed human habitats, influencing human biological and cultural evolution as well as their dispersal.

Specifically, the scientists found that various anatomically diverse hominin groups inhabited the area during a phase of long-lasting and relatively stable humid conditions from approximately 620,000 to 275,000 years BP (Before Present). However, a series of shorter abrupt and extreme arid pulses interrupted this long generally stable and wet phase. Most likely, this resulted in a fragmentation of habitats, shifts in population dynamics and even the extinctions of local populations. As a result, small, reproductively and culturally isolated populations then had to adapt to dramatically transformed local environments, likely stimulating the appearance of the many geographically and anatomically distinct hominin groups and the separation of our modern human ancestors from archaic groups.

A phase with significant climate swings resulting in regularly transformed habitats in the area from approximately 275,000 to 60,000 years BP repeatedly resulted in environmental shifts from lush vegetation with deep fresh water lakes to highly arid landscapes with the extensive lakes reduced to small saline puddles. In this phase, the population groups gradually transitioned from Acheulean technologies (oval hand axes made of stone and primarily associated with Homo ergaster/erectus) to more sophisticated Middle Stone Age technologies. This crucial phase also encompasses the emergence of Homo sapiens in eastern Africa as well as key human social, technological, and cultural innovations that could have buffered early Homo sapiens from the impacts of severe environmental changes. ‘These innovations, such as more varied toolkits and long-distance transport, would have equipped modern humans with an unprecedented adaptability to the repeated expansions and contractions of habitats,’ said Dr Foerster, the paper’s lead author.

The phase from approximately 60,000 to 10,000 years BP saw the most extreme environmental fluctuations, but also the most arid phase of the entire record, which could have acted as a motor for continuous indigenous cultural change. The scientists believe that the brief alignment of humid pulses in eastern Africa with wet phases in north-eastern Africa and the Mediterranean was key to opening favourable migration routes out of Africa on a roughly north-south axis along the East African Rift System (EARS) and into the Levant, facilitating the global dispersal of Homo sapiens.

‘In view of current threats to the human habitat from climate change and the overuse of natural resources through human activity, understanding how the relationship between climate and human evolution has become more relevant than ever,’ Foerster concluded.

This research is part of the Hominin Sites and Paleolakes Drilling Project (HSPDP). In order to evaluate the impact that different timescales and magnitudes of climatic shifts have had on the living conditions of early humans, the project has cored five lake archives of climate change during the last 3.5 million years. All five sites in Kenya and Ethiopia are located in close vicinity to paleoanthropological key sites covering various steps in human evolution, with the site in southern Ethiopia exploring the youngest chapter.

As part of HSPDP, the project has received funding from the International Continental Scientific Drilling Program (ICDP), the German Research Foundation (DFG), the Natural Environment Research Council (NERC), the National Science Foundation (NSF), and the DFG Collaborative Research Centre 806 ‘Our Way to Europe’. CRC 806 was based at the universities of Cologne, Bonn, and Aachen and received generous financial and infrastructural support from these institutions from 2009 to 2021.

A new study used eye-tracking technology to show that kids’ attention wandered all over a computer screen while they were trying to complete a task — even when adults quickly figured out they could do the task more efficiently by focusing on particular objects.

But that tendency to have a wandering eye helped 4- and 5-year-olds when the task unexpectedly changed — and they noticed important things on the screen that adults were not paying attention to.

“The ability of adults to focus their attention is usually very helpful in everyday life,” said Vladimir Sloutsky, co-author of the study and professor of psychology at The Ohio State University.

“But sometimes it helps to see the world more as a kid and to notice things that may not seem that important or relevant at the time.”

Sloutsky conducted the research with Nathaniel Blanco, a postdoctoral researcher, and Brandon Turner, professor, both in psychology at Ohio State. The study was published online recently in the Journal of Experimental Child Psychology.

The study involved 30 4- and 5-year-old children and 38 adults who participated in a lab, where they were fitted with eye trackers that could tell where they looked on a computer screen.

They were then shown colorful images of creatures that had seven identifiable features, including a head, tail and antennae.

Participants were told there were two types of creatures, called Flurps and Jalets, and that they had to figure out which ones were which.

One feature was always different on the two types of creatures — for example, the Jalets may have a blue tail and the Flurps an orange tail. In addition, the children and adults were told that most (but not all) of the Flurps had a certain type of feature, such as pink antennae.

One of the features was never mentioned in the instructions and it did not differ between the types of creatures. This was what the researchers called the “irrelevant feature.”

After training, participants were shown a series of images of the creatures on the computer screen and were told to indicate which type of creature each one was.

During the first part of the experiment, adults quickly learned which feature always determined whether the creature was a Flurp or Jalet, and the eye-tracker showed that they then concentrated nearly all of their attention on that feature.

Children were slower to learn which feature was most important in determining which creature was which — and the eye-tracker showed they continued to look at all the features of the two creatures, even the ones that were not relevant.

“The kids were not as efficient as adults at learning quickly,” Sloutsky said. “They kept looking around even when they didn’t need to.”

But halfway through the experiment, the researchers made an unannounced switch: The irrelevant feature — the body part that previously had no bearing on what type of creature it was — became the feature that would determine whether it was a Flurp or a Jalet. This feature, which had been the same for both creatures before the switch, was now different for each.

After the switch, the adults were more oblivious to the importance of the new feature than the children were. Instead, they were relying on the previously learned less-important features.

Children, on the other hand, had been paying attention to everything, so they noticed more swiftly that the rules had changed.

“The adults were suffering from learned inattention,” Sloutsky said. “They weren’t paying attention to features that weren’t important during the first part of the experiment, so they missed when those features did become important.”

Sloutsky said the brains of 4- and 5-year-olds aren’t mature enough to focus attention in the way adults do. That fact may help them learn more as they explore the world.

And adults certainly have the ability to distribute their attention broadly like the children did in this study — but they often choose selective attention because it is helpful in achieving efficiency, he said.

The lesson for adults, though, is to realize that selective attention, while increasing the efficiency of learning and performance, can also lead to a learning trap in some situations, Sloutsky said.

“When you know something really well or a solution to a problem seems obvious, it may help to broaden your attention, to look for clues that may not seem relevant at first — to think like a kid again.”

The study was supported by grants from the National Institutes of Health.

The high cost of powering an underwater camera for a long time, by tethering it to a research vessel or sending a ship to recharge its batteries, is a steep challenge preventing widespread undersea exploration.

MIT researchers have taken a major step to overcome this problem by developing a battery-free, wireless underwater camera that is about 100,000 times more energy-efficient than other undersea cameras. The device takes color photos, even in dark underwater environments, and transmits image data wirelessly through the water.

The autonomous camera is powered by sound. It converts mechanical energy from sound waves traveling through water into electrical energy that powers its imaging and communications equipment. After capturing and encoding image data, the camera also uses sound waves to transmit data to a receiver that reconstructs the image.

Because it doesn’t need a power source, the camera could run for weeks on end before retrieval, enabling scientists to search remote parts of the ocean for new species. It could also be used to capture images of ocean pollution or monitor the health and growth of fish raised in aquaculture farms.

“One of the most exciting applications of this camera for me personally is in the context of climate monitoring. We are building climate models, but we are missing data from over 95 percent of the ocean. This technology could help us build more accurate climate models and better understand how climate change impacts the underwater world,” says Fadel Adib, associate professor in the Department of Electrical Engineering and Computer Science and director of the Signal Kinetics group in the MIT Media Lab, and senior author of the paper.

Joining Adib on the paper are co-lead authors and Signal Kinetics group research assistants Sayed Saad Afzal, Waleed Akbar, and Osvy Rodriguez, as well as research scientist Unsoo Ha, and former group researchers Mario Doumet and Reza Ghaffarivardavagh. The paper is published in Nature Communications.

Going battery-free

To build a camera that could operate autonomously for long periods, the researchers needed a device that could harvest energy underwater on its own while consuming very little power.

The camera acquires energy using transducers made from piezoelectric materials that are placed around its exterior. Piezoelectric materials produce an electric signal when a mechanical force is applied to them. When a sound wave traveling through the water hits the transducers, they vibrate and convert that mechanical energy into electrical energy.

Those sound waves could come from any source, like a passing ship or marine life. The camera stores harvested energy until it has built up enough to power the electronics that take photos and communicate data.

To keep power consumption as a low as possible, the researchers used off-the-shelf, ultra-low-power imaging sensors. But these sensors only capture grayscale images. And since most underwater environments lack a light source, they needed to develop a low-power flash, too.

“We were trying to minimize the hardware as much as possible, and that creates new constraints on how to build the system, send information, and perform image reconstruction. It took a fair amount of creativity to figure out how to do this,” Adib says.

They solved both problems simultaneously using red, green, and blue LEDs. When the camera captures an image, it shines a red LED and then uses image sensors to take the photo. It repeats the same process with green and blue LEDs.

Even though the image looks black and white, the red, green, and blue colored light is reflected in the white part of each photo, Akbar explains. When the image data are combined in post-processing, the color image can be reconstructed.

“When we were kids in art class, we were taught that we could make all colors using three basic colors. The same rules follow for color images we see on our computers. We just need red, green, and blue — these three channels — to construct color images,” he says.

Sending data with sound

Once image data are captured, they are encoded as bits (1s and 0s) and sent to a receiver one bit at a time using a process called underwater backscatter. The receiver transmits sound waves through the water to the camera, which acts as a mirror to reflect those waves. The camera either reflects a wave back to the receiver or changes its mirror to an absorber so that it does not reflect back.

A hydrophone next to the transmitter senses if a signal is reflected back from the camera. If it receives a signal, that is a bit-1, and if there is no signal, that is a bit-0. The system uses this binary information to reconstruct and post-process the image.

“This whole process, since it just requires a single switch to convert the device from a nonreflective state to a reflective state, consumes five orders of magnitude less power than typical underwater communications systems,” Afzal says.

The researchers tested the camera in several underwater environments. In one, they captured color images of plastic bottles floating in a New Hampshire pond. They were also able to take such high-quality photos of an African starfish that tiny tubercles along its arms were clearly visible. The device was also effective at repeatedly imaging the underwater plant Aponogeton ulvaceus in a dark environment over the course of a week to monitor its growth.

Now that they have demonstrated a working prototype, the researchers plan to enhance the device so it is practical for deployment in real-world settings. They want to increase the camera’s memory so it could capture photos in real-time, stream images, or even shoot underwater video.

They also want to extend the camera’s range. They successfully transmitted data 40 meters from the receiver, but pushing that range wider would enable the camera to be used in more underwater settings.

This research is supported, in part, by the Office of Naval Research, the Sloan Research Fellowship, the National Science Foundation, the MIT Media Lab, and the Doherty Chair in Ocean Utilization.

“Although asexuals don’t have the desire for sexual relationships, they nevertheless form romantic relationships and those connections look at least somewhat similar to non-asexuals’ romantic relationships,” said William Chopik, associate professor in MSU’s psychology department and coauthor of the study.

The study, published in Frontiers in Psychology, is among the largest studies of asexual individuals’ relationships ever conducted and the only one to examine what predicts commitment and longevity in their relationships. The study looked at a sample of 485 people who self-identified as on the asexual spectrum and are currently in a romantic relationship. This is one of the only published studies that allowed people to self-identify with any asexual spectrum label, in addition to allowing them to use any other sexual or romantic labels that fit.

“I sincerely hope that this study will more widely show the diversity of the asexual community, shed light on their experiences and show that being on the asexual spectrum does not preclude one from successful romantic relationships or love,” said coauthor and research associate Alexandra Brozowski.

The long-standing theory about what predicts who breaks up and who stays in relationships, called the Investment Model, says that people stay in relationships if they are happy and satisfied, if they have invested time and energy into the relationship and if they don’t have any other options. Many theories say that sex is a central part of romantic relationships, which doesn’t leave room for asexual relationships.

“We found that the same ingredients predict success in these relationships, so they’re not weird, bizarre, worse than or much different at all from non-asexual people’s relationships.” Chopik said. “The hope is that this destigmatizes asexual people’s relationships as just as satisfied and common as non-asexual people’s relationships.”

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