[Research now and in the future] Solving three mysteries in brain evolution

Why did the human brain get so big?

 

 
 I am currently working on research on the evolution of human intelligence, mainly focusing on language, but there are three big mysteries here.One is the explosive increase in brain capacity over time.Even before the emergence of the genus Homo, the brain gradually expanded, but while it did not differ much from that of modern apes, it expanded remarkably from the beginning of making stone tools [indicated by the red → in the figure below].How did this come about?
 

Evolution of intelligence that cannot be explained by brain size alone

 The second mystery is that the brain capacity of us Homo sapiens has not expanded so much from that of ancient humans (Heidelbergs and Neanderthals), and some studies have shown that it is actually shrinking.Moreover, despite being said to have appeared 25 years ago, symbolic artefacts such as paintings and sculptures were created, and the use of tools began about 20 years ago.Not only has no simple correspondence been found between brain size and human activities that lead us to the present day, but it is also a great mystery what happened during the approximately XNUMX years.
 

Why did ancient civilizations blossom almost simultaneously?

 The final mystery is more recent, 1 years after the end of the Ice Age, with the shift from hunting and gathering to farming, the Middle East, Africa, East Asia, South Asia, Central America, and South America. , Homo sapiens civilizations emerged and blossomed almost simultaneously all over the world.While these civilizations are diverse, they also have quite a few elements in common.why at the same timeThe brain did not grow during this time, and it is unlikely that the genetic variation in intelligence occurred by chance.This is the third mystery.

 One of the keys to unraveling these mysteries is the idea that there is something inherent in humans that can be called cognitive idiosyncrasies.In a little more simple terms, it's about assuming something called latent ability.Elements that constitute human-specific cognitive activities are also present in other animal species at an embryonic level.In fact, we have found that monkeys can use tools when kept in an experimental environment.In other words, in a natural environment, abilities cannot be demonstrated without a “cue”.However, the ability itself is equipped, and we think that we can do it, but we didn't do it.
 

 

The key to solving the mystery, ``three-dimensional niche construction''

 Supporting this way of thinking is the concept of "niche construction" and the concept of "three-tiered niche construction" that expands it into three layers.A niche is a habitat environment in nature that contains the resources necessary for a species to survive, and creating it yourself is niche construction.
 
 One of the three elements is the niche related to the environment, and "environmental niche construction" to create it.The genus Homo made tools for themselves, but tools have a definite "purpose".Therefore, in a society where tools have begun to spread, individuals are required to adapt to the use of tools, and this is gradually shared among the same generation or the next generation.I believe that through this process, the peculiar intentionality of human beings was exhibited, and an "environmental niche" was built at an accelerated pace.

 The other is "construction of a cranial nerve niche," which is related to cranial nerve tissue and function.As a new environment is created, the human brain is constantly modified in response to it.When a tool-free monkey is placed in a tool-using environment, the parietal lobe of the brain swells, creating new cranial nerve tissue that enables tool-adapted physical information processing.Creating new neural resources by adapting to the environment is called “brain niche construction”.

 The third is “cognitive niche construction,” which involves cognitive functions using the cranial nerves.Humans also use the cranial nervous system responsible for the spatial information processing function necessary for tool use, and perform information processing such as abstract language, mathematics, and social structure.In other words, it becomes possible to make new cognitions with the cognition mechanisms that were originally provided.I call it “cognitive niche building”.

 New cognition changes the environment.As a result, cranial nerve functions are modified and the brain develops.In this way, the cyclical interaction of the three niches is the “three-dimensional niche construction,” or to be precise, the first phase.As you gradually expand your niche structure, you'll likely accumulate latent capabilities that will serve you well in new niches.

 Homo sapiens must have gone through a turning point due to the use of tools and the three-dimensional niche mechanism, acquired unique abilities such as language, and reached the present level of intelligence.This is my current hypothesis.
★I have omitted the second phase of ternary niche construction.For those who want to know, please read "Cognitive Science Course 2 Mind and Brain 10 Brain - Environment - Intentional Driving Force of Human Evolution Hidden in the Circle of Cognition - Phase Transition of Three Niche Construction" scheduled to be released in October (Atsushi Iriki / Yumiko Yamazaki)”)

 So, will human intelligence continue to evolve further in the future?One of the hints is the progress of AI technology.

 It can be said that human evolution so far has been subject to physical and biological constraints such as brain structure and available resources.In fact, we know and think about only a handful of space-time.However, since the deep basic principle of ternary niche construction is not subject to physical constraints, I feel the possibility of breaking through this through the creation of a new conceptual space using AI and IoT.

 If we can make good use of these, we can combine Western science, which pursues the truth by decomposing things into the smallest units, and the Eastern worldview, which seeks to think about the universe and human beings while leaving ambiguity from the whole, and understanding of human beings. I have a dream that it may be possible to fuse with and even change the existing scientific framework.
 

 

Message to high school students

 It's fun to hear other people's success stories, but don't take them for granted.That person's success was brought about by their personality and the circumstances they were in at the time, and it is unlikely that the conditions will be the same as yours.However, you may be able to discern some secrets behind the success stories and use them to your advantage.

 Based on these assumptions, the important thing for everyone is that if there is something you want to do, do it.Of course, I have also experienced it, but there are not many opportunities to do what you want from the beginning.Most of the time, the only thing you can do is pick the closest thing you can do right now and start from there.However, if you produce results, you will be recognized by those around you, and you will be given more challenges and options.And among them, there is always something close to what I want to do.

 My experience is that as I repeated this process, I gradually came closer to what I really wanted to do.Of course, don't forget what you wanted to do in the first place.

  On the other hand, in the above situation, I think we have no choice but to gradually create an environment where we can do what we want.As I have already mentioned, when I was young I was interested in language, which is the object of humanities, and from that point I wanted to study humans scientifically.What we can do is what we now call interdisciplinary research.However, at that time, there were few universities that could conduct such research.If you go into the natural sciences, you won't be able to study humanities, and vice versa.

 Therefore, while doing what I can do now, I have been working with enthusiasm to revise the existing scientific framework by myself.It is the younger generation who have flexible ideas.Whether you want to become a researcher in the future or be active in government or business, I would like you to always have the spirit to pioneer new fields and take on any challenge.
 
 

RIKEN Center for Biosystems Dynamics Research

Team Leader Dr. Atsushi Iriki

1986年東京医科歯科大学大学院歯学研究科修了、1986年東京医科歯科大学歯学部助手(口腔生理学講座)、1987年ロックフェラー大学(アメリカ)助手、1990年東邦大学医学部助手(生理学第一講座)、 1991年同講師、1997年同助教授、1999年東京医科歯科大学医歯学総合研究科教授(認知神経生物学)、2005年理化学研究所脳科学総合研究センターチームリーダー、 2018年理化学研究所生命機能科学センター チームリーダー、1986年歯学博士、東京医科歯科大学、1991年博士(医学)東邦大学。長野県長野高等学校出身。

 

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