Complex cognition shaped the Stone Age hand axe, study shows

Even with extensive training, the modern mind finds it challenging to make an Acheulean hand axe. "We should have respect for Stone Age tool makers," says experimental archeologist Dietrich Stout. Photo by Carol Clark.

By Carol Clark

The ability to make a Lower Paleolithic hand axe depends on complex cognitive control by the prefrontal cortex, including the “central executive” function of working memory, a new study finds. 

PLOS ONE published the results, which knock another chip off theories that Stone Age hand axes are simple tools that don’t involve higher-order executive function of the brain.

“For the first time, we’ve showed a relationship between the degree of prefrontal brain activity, the ability to make technological judgments, and success in actually making stone tools,” says Dietrich Stout, an experimental archeologist at Emory University and the leader of the study. “The findings are relevant to ongoing debates about the origins of modern human cognition, and the role of technological and social complexity in brain evolution across species.”

The skill of making a prehistoric hand axe is “more complicated and nuanced than many people realize,” Stout says. “It’s not just a bunch of ape-men banging rocks together. We should have respect for Stone Age tool makers.”

The study’s co-authors include Bruce Bradley of the University of Exeter in England, Thierry Chaminade of Aix-Marseille University in France; and Erin Hecht and Nada Khreisheh of Emory University.

Stone tools – shaped by striking a stone “core” with a piece of bone, antler, or another stone – provide some of the most abundant evidence of human behavioral change over time. Simple Oldowan stone flakes are the earliest known tools, dating back 2.6 million years. The Late Acheulean hand axe goes back 500,000 years. While it’s relatively easy to learn to make an Oldowan flake, the Acheulean hand axe is harder to master, due to its lens-shaped core tapering down to symmetrical edges.



“We wanted to tease apart and compare what parts of the brain were most actively involved in these stone tool technologies, particularly the role of motor control versus strategic thinking,” Stout says.

The researchers recruited six subjects, all archeology students at Exeter University, to train in making stone tools, a skill known as “knapping.” The subjects’ skills were evaluated before and after they trained and practiced. For Oldowan evaluations, subjects detached five flakes from a flint core. For Acheulean evaluations, they produced a tool from a standardized porcelain core.

At the beginning, middle and end of the 18-month experiment, subjects underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) scans of their brains while they watched videos. The videos showed rotating stone cores marked with colored cues: A red dot indicated an intended point of impact, and a white area showed the flake predicted to result from the impact.

The subjects were asked the following questions: “If the core were struck in the place indicated, is what you see a correct prediction of the flake that would result?” “Is the indicated place to hit the core a correct one given the objective of the technology?”

The subjects responded by pushing a “yes” or “no” button.

Answering the first question, how a rock will break if you hit it in a certain place, relies more on reflexive, perceptual and motor-control processes, associated with posterior portions of the brain. Stout compares it to the modern-day rote reflex of a practiced golf swing or driving a car.

The second question – is it a good idea to hit the core in a certain spot if you want to make a hand axe – involves strategic thinking, such as planning the route for a road trip. “You have to think about information that you have stored in your brain, bring it online, and then make a decision about each step of the trip,” Stout says.

This so-called executive control function of the brain, associated with activity in the prefrontal cortex, allows you to project what’s going to happen in the future and use that projection to guide your action. “It’s kind of like mental time travel, or using a computer simulation,” Stout explains. “It’s considered a high level, human cognitive capacity.”

The researchers mapped the skill level of the subjects onto the data from their brain scans and their responses to the questions. Greater skill at making tools correlated with greater accuracy on the video quiz for predicting the correct strategy for making a hand axe, which was itself correlated with greater activity in the prefrontal cortex.

“These data suggest that making an Acheulean hand axe is not simply a rote, auto pilot activity of the brain,” Stout says. “It requires you to engage in some complicated thinking.”

Most of the hand axes produced by the modern hands and minds of the study subjects would not have cut it in the Stone Age. “They weren’t up to the high standards of 500,000 years ago,” Stout says.

A previous study by the researchers showed that learning to make stone tools creates structural changes in fiber tracts of the brain connecting the parietal and frontal lobes, and that these brain changes correlated with increases in performance. “Something is happening to strengthen this connection,” Stout says. “This adds to evidence of the importance of these brain systems for stone tool making, and also shows how tool making may have shaped the brain evolutionarily.”

Stout recently launched a major, three-year archeology experiment that will build on these studies and others. Known as the Language of Technology project, the experiment involves 20 subjects who will each devote 100 hours to learning the art of making a Stone Age hand axe, and also undergo a series of MRI scans. The project aims to hone in whether the brain systems involved in putting together a sequence of words to make a meaningful sentence in spoken language overlap with systems involved in putting together a series of physical actions to reach a meaningful goal.

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WaterHub recycles wastewater to heat and cool buildings

Click here if video does not appear on screen.

Emory's WaterHub replicates the natural system of a wetland to recycle and treat sewer water so that it can be used to heat and cool the campus buildings. The facility is the first of its kind in the nation. You can take a tour of the facility this Friday, located behind the sorority houses on Eagle Row, as part of the grand opening of the WaterHub. Watch the video to learn more.

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Climate@Emory: Change is in the air

Steve Sclar, left, recently demonstrated on the Emory campus how he gathers indoor air quality data. (Emory Photo/Video)

By Carol Clark

Steve Sclar traveled to Golog Tibetan Autonomous Prefecture in China last summer to research the indoor air quality of nomads, who burn yak dung in their stoves for warmth and to cook their food. His measurements showed high levels of fine particulate matter in the smoked-filled tents and homes of some of the nomads. But Sclar also caught a glimpse of how global pollutants from industrialization may be impacting the isolated realm of the Tibetan plateau.

"The Tibetans are noticing changes in their climate and they're worried about the effects," says Sclar, an MPH student in Rollins School of Public Health's Department of Environmental Health. "Their grassland is getting poorer in the summer months and they see the snow pack getting smaller on the holiest mountain range in the region, known as Amnye Machen.

"I asked one nomad, 'What happens if Amnye Machen loses all of its snow?' He told me, 'Then it's the end of the world.'"

Climate change "is the biggest environmental health problem we face," Sclar says, "and yet it is so hard to pin down. There's no one country or entity to blame, and there is no one field of study that has the solution. We need to figure out how to reconcile all this."

Climate@Emory is an initiative made up of more than 50 faculty and staff from 20 departments across the university. Its goal is to harness Emory's strengths to help it play a leading role in the global response to perhaps the most complicated and pressing problem of our time. Since its launch last fall, the initiative has worked to support, connect and expand Emory's climate-related scholarship, teaching and community engagement.

"It's really not possible to understand climate change from the standpoint of any one discipline," says Eri Saikawa, who is Sclar's adviser and one of the founders of Climate@Emory. She is an assistant professor at Rollins and in the Department of Environmental Sciences. "We want to connect the dots to improve the quality and impact of Emory's research and provide a platform for intellectual engagement on climate change."

Read more in Emory Report.

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How zinnias shaped a budding biologist, and other fun facts about plants

"We're tied into plants in myriad and intricate ways," says biologist Roger Deal, who studies how plants build and adapt their bodies.

By Carol Clark

“I’ve always been really fascinated by plants, even from a young age,” says Emory biologist Roger Deal. “Their lives are so interesting, even though they are stuck where they are born.”

Deal's roots are in Columbia, South Carolina, where his father was a physician and his mother loved to garden.

“My first plants were zinnias,” he recalls. “I was about 10 and my mom and I went to the garden store where I picked out a packet of seeds. You have these little dry things that look like pieces of dust. All you have to do is put them in the ground and get them wet, and then you have a whole organism. I thought, ‘Wow, what an amazing life cycle! How does it work?’”

Roger Deal

Plants go back millions of years, when the Earth’s atmosphere contained very little oxygen. “Where did all that extra oxygen come from? It’s a byproduct of plants,” Deal says. “All the energy that we need to live also comes from plants. And they’re beautiful – they’re an important part of our aesthetic. We are basically tied into plants in myriad and intricate ways.”

As an undergraduate at the University of South Carolina, Deal worked in a lab that studied phytoremediation, or the process of using plants to clean up pollution. “A lot of plants are tolerant of heavy metals,” he explains. “I worked on a project that was exploring how to use Spartina, the grass you see growing along salt marshes on the coast, to suck mercury pollution up out of the soil.”

Deal became interested in how genes are controlled in plant development during his graduate school years at the University of Georgia.

In his lab at Emory, he’s continuing this focus on how plants build and adapt their bodies. By digging deep into the developmental biology and genetics of plant systems, he hopes to unearth secrets that could benefit both agriculture and human health.

“A big question in studying the genome of any organism is figuring out where all the genes are, and how you put all the parts together to build an organism,” he explains. “Humans have a parts list of about 30,000 different genes, for example, but only 2 percent of our genome is genes. The rest was once considered junk DNA, but we now know that it’s not junk.”

Watch a video of Roger Deal:


DNA is not just floating around by itself in the nucleus of a cell. It’s wrapped up in little globules of proteins called histones. By wrapping tightly around histones, a six-meter long strand of DNA can cram into a cell nucleus.

“This complex of histones and DNA is called chromatin,” Deal says. “The chromatin is used to turn genes on or off, which determines the function of a cell. So chromatin is part of the system that differentiates the cells when an embryo is growing. Chromatin is also involved in establishing and maintaining cell proliferation. If cell proliferation gets turned on inappropriately, the result can become a tumor.”

One of the model organisms Deal’s lab uses is Arabidopsis thaliana, a small flowering plant that is a member of the mustard family. “It’s just a lowly little weed that you’ve probably stepped on and not noticed,” Deal says of Arabidopsis. “It grows all over the northern hemisphere.”

The Arabidopsis genome is about one-twentieth the size of the human genome. “It’s sort of streamlined,” Deal says. “It has about the same number of genes as we do, but it has way less ‘intergenic’ DNA. So in terms of finding the regulatory parts, we have a lot less stuff to look at. When it comes to lab research, Arabidopsis is like the fruit fly of the plant world.”

Arabidopsis thaliana (NIH)

Arabidopsis plants begin their life as the fusion of a sperm and an egg: A single cell, which develops into an embryo inside of a seed. “This little embryo can sit there for decades,” Deal says. “But once it gets wet, the whole thing kicks into action. Suddenly, it starts growing, pops a root, develops leaves.”

At some point, the plant switches from vegetative growth to reproductive growth. “Something in the environment, the length of the day, the quality of light, tells these plants it’s time to stop making leaves and start making flowers,” Deal says. “A really important question is how this switch operates at the molecular level.”

A key part of the puzzle appears to be a histone protein called H2AZ, which is an important component of chromatin in plants, animals and fungi.

“The H2AZ gene is essential for life in animals,” Deal says. “If an embryo doesn’t have it, the embryo stops developing and dies. But an overproduction of an H2AZ molecule appears to drive the genesis of several types of cancer, including breast and prostate cancer.”

Plants, unlike laboratory rats, can survive without the H2AZ gene. “If you knock out the H2AZ gene in Arabidopsis plants they don’t die, it just messes them up,” Deal says. “The lack of H2AZ affects the leaf size, flowering time and their susceptibility to pathogens and other stresses.”

That makes Arabidopsis an easily accessible model to study this particular gene and its on-and-off switch. “We can mess with Arabidopsis in pretty extreme ways, removing this critical regulator of a process, and then study what happens at the molecular level,” Deal says. “We’re hoping that our research will help us understand something about the biology of cancer and the biology of animal and plant development all in one fell swoop.”

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Physicist's research of glassy materials nets NSF CAREER award

Physicist Justin Burton at work in his lab, where he studies amorphous matter. (Emory Photo/Video)

By Carol Clark

Emory physics professor Justin Burton received a $625,000 award from the National Science Foundation’s Faculty Early Career Development (CAREER) Program. The five-year CAREER grants, among the NSF’s most prestigious awards, support scientists who exemplify the role of teacher-scholars through outstanding research integrated with excellence in education.

Burton will apply the award to his research into amorphous matter, or substances made up of granules in jumbled, irregular states. These substances include everything from the foam on your cup of cappuccino to the vast, slushy mélange of a glacier as it breaks down and flows into the sea. Amorphous matter also encompasses soft condensed matter such as toothpaste, shaving cream, plastic and glass, which are collectively known as “glassy” materials.

“Amorphous material is everywhere, it’s among the most common states of solid matter,” Burton says, “and yet, there’s a lot that we don’t understand about it.”

Crystalline material, by contrast, is relatively rare but well understood by physicists. Crystals have a structural order that makes them easier to conceptualize and define mathematically. “Research into the thermodynamic behavior of crystals at ultra-low temperatures led to our understanding of how they conduct heat,” Burton says. “That’s one of the fundamental triumphs of quantum mechanics. It helped lay the foundation for a lot of important tools of the modern world, from computers to cell phones.”

Lacking the well-defined order of crystals, amorphous materials often behave in peculiar, unpredictable ways. Burton uses the example of a pile of sand at the bottom of an hourglass. “What seems stable enough can suddenly avalanche upon the addition of a few extra grains,” he says. “Or even a traffic jam: What determines the boundary between a flowing state and a rigid one? Our world is full of similar examples where systems exist in a region near marginal stability.”

A view inside the vacuum chamber, where colloidal particles are suspended in a flat disc, lit by the green light of a laser. Photo by Justin Burton.

Burton’s lab is creating model systems to simulate the dynamics of the microscopic granules of amorphous, glassy matter at ultra-low temperatures of below 1 degree Kelvin. That’s colder than the deepest reaches of space.

In a vacuum chamber, filled with argon gas, the lab conducts experiments. The chamber is filled with ionized argon gas. “It’s a plasma, or a gas that has had its electrons ripped away from its atoms,” Burton explains. “The electrons are constantly being ripped away and resembling.”

Colloidal particles, tiny as dust specks, are suspended in the plasma of the vacuum chamber, to stand-in for the molecules of an amorphous material. By altering the gas pressure inside the chamber, and varying the size of the particles, the lab members can study how the particles behave as they move between an excited, free-flowing state into a jammed, stable position.

They can also simulate how molecules in a stable position react to a disturbance. “We want to create a wave, like dropping a pebble into a still pond to make ripples, and study that dynamic,” Burton says. “That could help us understand, for instance, how sound moves through a glassy material.”

Burton’s lab will use another model, involving polymer hydrogel particles that expand or shrink in response to salt concentrations, to study Casimir forces, a special type of long-ranged force that can arise between objects in a highly fluctuating medium.

In addition to opening a window into the molecular motions common in glasses, the research could shed light on the connection between the dynamics and disorder in a broad range of physical systems, Burton says.

In parallel to his research effort, the CAREER award will also fund the creation of an after-school science club at an elementary school in Dekalb County. Burton and his graduate students will lead children in hands-on activities and experiments that give insights into basic principles of physics.

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