archaeology.org 45thinking. “There’s no way.”
To his surprise, both groups managed to craft
rudimentary hand axes. Once they had mastered
the basics, Putt had them make the tools while
wearing fNIRS sensors. Putt was looking for
differences between the two groups. Her theory
was that if language centers in the brain lit up
regardless of whether participants learned
with the sound on or off, it would be a
strong clue that tool use and language were
somehow related.
Instead, scans of dozens of participants
showed that the brain activity of those who
learned without hearing the instructions—
without language, in other words—looked dif-
ferent. In the toolmakers who learned just by
watching Woods, the brain’s language centers
were quiet; in the scans of people who learned
while listening, language centers lit up. What both
did have in common was activity in areas that connect
with working memory and the areas that process sounds and
images. The results were counterintuitive. Learning to use
and make Acheulean tools was not closely linked to
language centers, as evolutionary anthropologists
had assumed. “We’ve showed you can make a
hand ax without language,” Putt says.
Rather, Putt’s scans suggest that in the
absence of verbal instruction and language,
the brain relies on a combination of working
memory and motor control to make tools.
Research has shown it’s the same network
of neurons we use to make music. “Piano
playing uses almost the identical network
as toolmaking,” Putt says. “You’re coordi-
nating your hands while keeping in mind
all of these sub-goals.”
It’s an exciting result. Experiments on
modern humans may never conclusively
prove how our distant ancestors thought. But
the insights archaeologists and neuroscien-
tists are generating together are contributing
to our understanding of what makes us human.
And with neuroimaging techniques developing
fast, their potential to answer questions about our deep
past has barely been tapped. “The big picture is to look at
other points in time. Were Neanderthals as smart as humans?
We can test that, by comparing their tools to the Upper
Paleolithic tools humans were making,” Putt says. “We’re
focusing on one small snapshot, but humans have been
evolving for millions of years.” nAndrew Curry is a contributing editor at Archaeology.experiments haven’t shown yet is whether language was
also a required part of the package. “It’s very controver-
sial whether early hominin species had language,” says
Uomini. “For me, the big question is, How do language
and stone toolmaking draw on similar brain areas? Are
they overlapping brain areas, or not?”
If they are, it would be reasonable to guess that
language goes a long way back. Is it possibly a
critical clue to our evolution as a species and what
differentiates us from other animals, including
our close primate relatives? John Gowlett, an
anthropologist at the University of Liverpool,
argues that the ability to plan chains of
actions—such as those that go into forming
sentences or making Acheulean tools—is
an essentially human trait. “Animals like us
are unleashed by language. We have past,
present, and future,” Gowlett says. “Other
animals are tied to the present.”F
or the last eight years, Putt has
been working to test the idea that tool
use and language involve the same brain
areas. Early on, she turned to a lab on the University
of Iowa campus dedicated to using a new brain scan
technology called functional near-infrared spectros-
copy (fNIRS). Unlike the more familiar fMRI,
which requires people to lie motionless in a huge
apparatus, fNIRS is portable and allows subjects
to move and work while wearing the scanner,
whose sensors are nestled against the scalp using a
special snug cap. The technique works by shining
infrared light through the scalp and skull into the
brain—certain wavelengths pass easily through
skin and bone—and measuring how much
light is absorbed.
The technique works because blood that
is carrying oxygen soaks up light at a dif-
ferent rate than blood that has already
delivered its payload of oxygen to active
brain cells. Brain regions that are working
stand out from regions at rest. “If you’re
using one part of your brain more actively, it’s
going to be more oxygenated,” Putt says. “We
can measure in milliseconds what’s happening
and pinpoint, with great accuracy, where it’s
happening.”
Over the course of several years, Putt trained two dif-
ferent groups of volunteers to make Acheulean-style stone
hand axes. Both groups watched a video of Alex Woods shot
to show only his hands at work. The first group watched him
while listening to his instructions; the second watched the
same video, but with the sound turned off. At first, Woods
was deeply skeptical. “Sit down with a bunch of students,
with technology they hadn’t even seen, and try to get them
to make it with no verbal instruction whatsoever?” he recallsAn Acheulean hand ax (left) from the site of Omo and
an experimental teardrop-shaped sharp-edged tool
(below) made in the same toolmaking study