which releases more calories from food
to fuel this energetically expensive organ.
It isn’t only the number of neurons
that matters, but also where they are.
Our remarkable abilities probably stem
from having more neurons in our cerebral
cortex – the brain’s wrinkly outermost
layer – than other animals, says
Herculano-Houzel. This structure allows
us to develop more complex behaviours
rather than simply responding to stimuli.
“If you have a cortex, you are no longer
a slave to what happens around you. You
have the flexibility to choose to do things
otherwise,” says Herculano-Houzel.
What’s more, her team recently
discovered that across warm-blooded
animals, the number of neurons in
the cortex correlates with longevity.
Herculano-Houzel thinks this is also
a factor in our cognitive superiority:
humans take years to reach maturity. “We
take a really long time to put that brain
together,” she says. “All the while, you are
assimilating information from the world.”
Neurons aren’t the whole story: cells
called astrocytes also play an important
role in intelligence (see “What makes a
brain”, page 40). But the sheer computing
power afforded by our 16 billion cortical
neurons is likely to be the critical factor
behind our cognitive dominance.
Sam Wong34 | New Scientist | 22 June 2019
Eight wonders of
the human brain
The more we learn about our command centre, the more
mysteries arise. New Scientist goes in search of the biggest
I
nside your head is an
object capable of feats of
computation, creativity and
understanding unrivalled in
the known universe – and all using
the power of a 20-watt light bulb.
We have made huge strides in
understanding the human brain.
In recent years, we have discovered
that brain cells can regenerate and
pinned down what happens when
you start talking before you know
what you want to say. Yet, the more
we learn, the more we realise how
much we still don’t know. In the
following pages, we explore the
biggest questions about the brain
to reveal the mechanisms and
mysteries of this phenomenal
blob of grey goo.The human brain, we love to tell
ourselves, is exceptional. Other animals
might use tools or solve mazes, but can
they invent computers or write sonnets?
Yet even with our extraordinary mental
prowess, it isn’t easy to explain what
makes the human brain so special. At
around 1.5 kilograms, our brains are
about a third the weight of an elephant’s
and a fifth that of a sperm whale.
If body size is taken into account,
however, our brains are unusually large:
between seven and eight times what
would be expected for a mammal our
size. But this crude measure isn’t enough
to explain our intelligence. The brain-to-
body-size ratio of a capuchin monkey is
higher than that of a gorilla, yet gorillas
are considered smarter.
Clearly size isn’t everything. A more
important metric might be the number
of neurons – the brain’s processing units.
Humans have about 86 billion, according
to Suzana Herculano-Houzel of Vanderbilt
University in Tennessee, who has
pioneered methods to count them.
In fact, primate brains have more
neurons than other mammal brains of
comparable size. Humans, having the
largest brain of any primate, also have
the most neurons of any primate, and
probably any animal. This was possibly
enabled by the invention of cooking,What makes our brain special?
Features Cover story
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