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Tuesday, October 23, 2012
Complex Brains Half a Billion Years Old
What this discovery makes clear is that the emergence of a viable
multicell evolutionary protocol included the immediate development of
the complex brain we know. We are going to find that this is all
inevitable and with modest room for structural variation. The brain
can be thought of a a sphere of brain cells all sprouting a
connecting communication link or two feeding a nerve bundle that
connects to all else. It is all very neat and just like our kidney
and liver it has been generally conserved.
In the meantime complex life as we know it is generally half a
billion years old on Earth. That awareness was sorted out through a
working brain ever since is well worth pondering. I suspect that its
evolution is central to multicelluar life anyway and additionally
supports my conjecture regarding the centrality of choice in the
I am sure further discoveries will drive the time window even further
back but not too far as the multicellular world is the producer of
pushes back evolution of complex brains
by Staff Writers
Tucson AZ (SPX)
Oct 11, 2012
This picture shows a
nearly intact fossil of Fuxianhuia protensa. The inset shows the
fossilized brain in the head of another specimen. The brain
structures are visible as dark outlines. Credit: Specimen photo:
Xiaoya Ma; inset: Nicholas Strausfeld.
remarkably well-preserved fossil of an extinct arthropodshows
that anatomically complex brains evolved earlier than previously
thought and have changed little over the course of evolution.
According to University of Arizona neurobiologist Nicholas
Strausfeld, who co-authored the study describing the specimen, the
fossil is the earliest known to show a brain.
Embedded in mudstones
deposited during the Cambrian period 520 million years ago in what
today is the Yunnan Province in China, the approximately 3-inch-long
fossil, which belongs to the species Fuxianhuia protensa, represents
an extinct lineage of arthropods combining an advanced brain anatomy
with a primitive body plan.
The fossil provides a
"missing link" that sheds light on the evolutionary history
of arthropods, the taxonomic group that comprises crustaceans,
arachnids and insects.
The researchers call
their find "a transformative discovery" that could resolve
a long-standing debate about how and when complex brains evolved.
"No one expected
such an advanced brain would have evolved so early in the history of
multicellular animals," said Strausfeld, a Regents Professor in
the UA department of neuroscience.[
actually the demands were made at the same time multicell structures
arose and it will prove inevitable - arclein]
Strausfeld, paleontologists and evolutionary biologists have yet to
agree on exactly how arthropods evolved, especially on what the
common ancestor looked like that gave rise to insects.
"There has been a
very long debate about the origin of insects," Strausfeld said,
adding that until now, scientists have favored one of two scenarios.
Some believe that
insects evolved from the an ancestor that gave rise to the
malacostracans, a group of crustaceans that include crabs and shrimp,
while others point to a lineage of less commonly known crustaceans
called branchiopods, which include, for example, brine shrimp.
Because the brain
anatomy of branchiopods is much simpler than that of malacostracans,
they have been regarded as the more likely ancestors of the arthropod
lineage that would give rise to insects.
However, the discovery
of a complex brain anatomy in an otherwise primitive organism such as
Fuxianhuia makes this scenario unlikely. "The shape [of the
fossilized brain] matches that of a comparable sized modern
malacostracan," the authors write in Nature. They argue the
fossil supports the hypothesis that branchiopod brains evolved from a
previously complex to a more simple architecture instead of the other
This hypothesis arose
from neurocladistics, a field pioneered by Strausfeld that attempts
to reconstruct the evolutionary relationships among organisms based
on the anatomy of their nervous system. Conventional cladistics, on
the other hand, usually look to an organism's overall morphology or
molecular data such as DNA sequences.
Strausfeld, who holds
appointments in other UA departments including evolutionary biology
and entomology, has catalogued about 140 character traits detailing
the neural anatomies of almost 40 arthropod groups.
"There have been
all sorts of implications why branchiopods shouldn't be the ancestors
of insects," he said. "Many of us thought the proof in
the pudding would be a fossil that would show a malacostracan-like
brain in a creature that lived long before the origin of the
branchiopods; and bingo! - this is what this is."
Strausfeld traveled to
the Yunnan Key Laboratory for Palaeobiology at Yunnan University in
Kunming, China, to join his collaborator, Xiaoya Ma, a postdoctoral
fellow at London's Natural History Museum, in studying the brain
anatomies of various fossil specimens. In the institute's collection,
they came across the fossil of Fuxianhuia protensa described in the
"I spent a
frenetic five hours at the dissecting microscope, the last hours of
my visit there, photographing, photographing, photographing," he
said. "And I realized that this brain actually comprises three
successive neuropils in the optic regions, which is a trait of
malacostracans, not branchiopods."
Neuropils are portions
of the arthropod brain that serve particular functions, such as
collecting and processing input from sensory organs. For example,
scent receptors in the antennae are wired to the olfactory neuropils,
while the eyes connect to neuropils in the optic lobes.
When Strausfeld traced
the fossilized outlines of Fuxianhuia's brain, he realized it had
three optic neuropils on each side that once were probably connected
by nerve fibers in crosswise pattern as occurs in insects and
malacostracans. The brain was also composed of three fused segments,
whereas in branchiopods only two segments are fused.
there are always only two visual neuropils and they are not linked by
crossing fibers," Strausfeld said. "In principle,
Fuxianhuia's is a very modern brain in an ancient animal."
The fossil supports
the idea that once a basic brain design had evolved, it changed
little over time, he explained. Instead, peripheral components such
as the eyes, the antennae and other appendages, sensory organs, etc.,
underwent great diversification and specialized in different tasks
but all plugged into the same basic circuitry.
"It is remarkable
how constant the ground pattern of the nervous system has remained
for probably more than 550 million years," Strausfeld added.
"The basic organization of the computational circuitry that
deals, say, with smelling, appears to be the same as the one that
deals with vision, or mechanical sensation."
The discovery will be
published in the the journal Nature.