In his book “The Triune Brain in Evolution” American physician and neuroscientist Paul
Donald MacLean proposed the Triune Brain Model of the evolution of the vertebrate forebrain
and behavior. The triune brain, according to him, consists of the reptilian complex,
the paleomammalian complex, or the limbic system, and the neomammalian complex or the
neocortex. This theory which neuroscientists now agree is an oversimplification of reality,
may still provide some real insight into the nature and potential diversity of alien minds
on other worlds. So today, we will be discussing some possible alien lifeforms under the Triune
Brain Model. But before we begin, be sure to subscribe to our channel if you enjoy content
like this!
The appearance of intelligence on Earth evolved in two major classes of animal nervous systems,
called ganglionic and chordate. But although the ganglionic system has proved an enormous
success on Earth among all invertebrates when it comes to data processing techniques to
ensure a species survival, there has been virtually no improvement in this design in
all the hundreds of millions of years following its emergence. Why is this the case? And would
it be possible for extraterrestrials to develop extremely high intelligence using a ganglionic
nervous system?
Well, chances are strongly against it. Evolutionary biologists believe that the system simply
is too complicated when it is scaled up in size. With more and more units, ganglia become
inefficient and difficult to carry or move because of their size, shape, and weight.
While invertebrates tend to be restricted to smaller sizes for unrelated technical reasons,
it is also true that large invertebrates of greater mass than vertebrates are not nearly
as intelligent. For example, many lobsters are larger than squirrels, and many squids
are vastly bigger than most vertebrates and yet these ganglionic creatures consistently
are less intelligent kilogram for kilogram. The system itself appears to be at fault.
Furthermore, it has also been suggested that the ganglionic system is self-limiting. The
typical invertebrate structure has only enough room to accommodate programmed "hard-wired"
behavior, with no space left over for surplus neural matter that might eventually evolve
and enlarge into higher intellect. Another factor is that the endless cross-connections
within the body can become so entangled and interwoven that they actually begin to strangle
other body organs.
So, a long time ago, a small group of organisms set out to explore a completely new system
of neurological organization. These chordates, including vertebrates and a few others, began
to experiment with "neural monarchy." This central nervous system allowed for any number
of additional sensory, analytical, or information-processing units to be plugged into the "central data
bus" without the setbacks of the ganglionic system. For example, with this simple invention,
organisms could now evolve to any size yet continue to increase their intelligence simply
by plugging in more "peripherals." Also, their spinal column could now grow into something
far more massive than ganglionic nerve nets, yet never entangle or choke off other organs
of the body. The simple brain was more compact and had plenty of room in which to expand.
Over millions of years, it provided for the growth of surplus neural matter that eventually
evolved into higher intellect here on Earth.
So, this "central nervous system" should most likely be the intelligence of choice for sentient
extraterrestrials even though it represents only a tiny percentage of all living animal
species on Earth. Moreover, according to most neurophysiologists, if the ganglionic or "distributed
brain" is the wrong path for higher intelligence, then it is almost certain that many alien
races in our universe will have made the same crucial discovery during their long evolutionary
journey. Now, aliens on other worlds may have discovered other alternatives to the ganglia
and the central notochord, or spinal column, but we know for certain that the path of the
chordates is a sound one, and this is why we expect the idea of notochords and brains
to be familiar to aliens as well.
But even if evolution on our world has selected the optimum basic configuration for neural
components in the development of intelligence, we cannot expect the specifics of brain development
on alien worlds to be exactly like our own. Among chordates, the most ancient component
of the central nervous system is the plug-in spinal cord. So, all sorts of interesting
subsystems and advanced modifications could be hooked on as the organisms grew in size
and complexity. But evolution works in such a way that once something original and extraordinary
has been invented, it is generally retained and not thrown away. The new is built upon
the old but does not replace it. This idea leads into MacLean’s theory of the Triune
Brain. He believes that this is exactly how the human brain evolved over the years.
For him, the story of man’s brain involves the slow formation, over evolutionary timescales,
of three successive and overlapping brain structures that were plugged into the neural
framework, modular style but which were never removed once nature was through with them.
Following each evolutionary step, the older more primitive modules were left in place
and the new ones were plugged in on top of them.
According to MacLean then, the human triune brain "amounts to three interconnected biological
computers, each with its own special intelligence, its own subjectivity, its own sense of time
and space, its own memory, motor, and other functions." Each of these brains represents
a major new evolutionary step. Now, because the current human brain has this unique tripartite
structure, and since each of the primitive components is still present and operational,
"we are obligated to look at ourselves and the world through the eyes of three quite
different mentalities."
The earliest of the three human plug-in brain systems has been called the "reptilian brain."
This structure surrounds the midbrain in the neural frame and probably arose 300 million
years ago with the rise of the first reptiles.
The second unit was laid over the first, eventually taking over the higher organismic functions.
This unit is called the "limbic brain," and probably arose about 150-200 million years
ago with the emergence of the first mammals on Earth.
The third and final unit, which appears in most of the higher mammals, is the neocortex.
This structure began to develop about 30 million years ago as a small growth on top of the
limbic system, slowly spreading, enlarging, becoming more massive overtime, finally reaching
the peak of accelerated development a few million years ago with the rise of humans.
The neocortex now completely encloses the underlying layers of the reptilian and limbic
brain. It is more central to neurological control functions in humans than the other
two systems.
Each of these brains has a different way of looking at the world. Each has a different
mode of operation. And yet each is functioning simultaneously within our heads, causing unusual
psychological conflict and, much of what is interesting about human behavior. For example,
the reptilian brain is known to play a role in aggressive behavior, the limbic brain appears
to generate strong, vivid emotions of various kinds, while the neocortex is responsible
for higher human cognitive functions. So, a combination of all three of these mentalities
is what makes us who we are according to this scheme.
Now, what do xenobiologists, or scientists who study alien life, have to say about all
of this? For them, it is not unreasonable to suppose that alien evolutionary patterns
may also include some form of a neural framework with plug-in components just like our own.
Certainly, this evolutionary path is an adaptive course of development that encourages survival.
But even then, expecting that natural selection on other planets will produce exactly the
same neural structural overlays as our own is not very reasonable. Aliens on other worlds
may have only two higher brain systems, or four, instead of our basic three. And as a
result, the distribution of behavioral functions and memory subsystems will likely be vastly
different from ours.
Nonetheless, it is not farfetched to imagine alien beings who possess three overlapping
brain systems that we humans have here on Earth. However, there is no reason to assume
that their evolutionary journey will lead them to develop the exact same overlapping
brain structure as ours. Planetary conditions and other such factors may perhaps lead to
the reptilian brain dominating the other two systems giving rise to Reptilian Intelligence.
Or it may be the case that the limbic brain prevails on some other alien worlds leading
to what we would call Limbic Intelligence. And even if the Neocortex dominates alien
minds, it may not be like our own but vastly different from us humans due to different
initial conditions. So, what would even be the mentality of such creatures? How will
they compare to us in their approach to life and everything else?
Well, we will go into details on each of these alien types and what they may look like, and
how they behave at a later date. For now, we will finish off the video here and give
you some time to think about this interesting topic! If you enjoyed this video and want
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let us know your thoughts in the comment section down below. Until then, we’ll see you in
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