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Why We Need to Study the Brain’s Evolution in Order to Understand the Modern Mind

The views expressed are those of the author and are not necessarily those of Scientific American.


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Image via Wikimedia Commons, adapted from Christopher Walsh, Harvard Medical School, by Gary2863

In the September 17th issue of The New Yorker, Anthony Gottlieb analyzes Homo Mysterious: Evolutionary Puzzles of Human Nature, a new book by David Barash, a psychology professor at the University of Washington in Seattle. Gottlieb’s article is more than just a book review—it’s also the latest in a long line of critiques of evolutionary psychology, the study of the brain, mind and behavior in the context of evolution.

Gottlieb makes several excellent points, describing the same major shortcomings of evolutionary psychology that critics and proponents alike have named many times before: frustratingly scant evidence of early humans’ intellect, the immense difficulty of objectively testing hypotheses about how early humans behaved, the allure of convenient just-so stories to explain the origins of various mental quirks and talents. Some of his points are less relevant, such as psychologists’ oft-lamented dependence on American and European college students as study subjects—this is a problem for all of psychology, not just evolutionary psychology.

One of Gottlieb’s arguments stunned me—an argument so weak that it disintegrates when probed, like a flake of sandstone. “In theory, if you did manage to trace how the brain was shaped by natural selection, you might shed some light on how the mind works,” Gottlieb writes. “But you don’t have to know about the evolution of an organ in order to understand it.”

Yes, you do.

Gottlieb gives the example of English physician William Harvey, who “figured out how [the heart] works two centuries before natural selection was discovered.” As precise, detailed and beautiful as Harvey’s descriptions of the heart and circulatory system were, they did not explain the origins of the heart as a functional organ. Why do different animals have different kinds of hearts? Why do some animals have blood but no heart?  When, how and why did hearts arise in the first place? Simply knowing how the heart works is not sufficient to answer these important questions. Rather, one needs to understand how the heart evolved. Such understanding contributes to more than basic biology—it also advances medicine. Tracing how gene expression in heart cells has changed over evolutionary time, for example, has simultaneously improved our understanding of congenital heart defects.

Just as evolution shaped the human heart’s structure and function, evolution sculpted the human brain—as well as the mind. This is an inescapable fact. The brain and mind are inextricable. In order to understand one, you must understand the other. Changing a brain’s structure changes how that brain behaves and what kind of mind emerges from its interaction with the environment. We have clear evidence of this from people who have endured swift and dramatic changes to their brains through traumatic injury, stroke and neurodegenerative diseases like Alzheimer’s. Likewise, the more gradual structural changes to the human brain during the course of its evolution mirror an evolution of the human mind. Consciousness, self-awareness, complex emotions, language, creativity—if you want to truly understand these aspects of mind, you must understand when and why they first evolved. To do that, you must understand how the brain has changed over time.

The evolutionary story of the human brain begins where life itself began: the ocean. The brain’s most basic building blocks have existed for billions of years: some of the simplest and oldest single-celled organisms use the same chemical messengers that our own brain and nervous system depend on. Sponges, one of the earliest groups of animals to have evolved, do not have nervous systems, but they do have some of the same genes and proteins that are essential for the construction of neural connections in our brain. The cells in a sponge’s body also communicate with waves of calcium ions not unlike the cascades of charged particles that surge down neurons in more complex animals. Jellyfish and their gelatinous relatives may have been the first group of animals to evolve genuine neurons—long, thin, branching cells adapted for the task of transmitting messages from one part of animal’s body to another. But these neurons were arranged in a diffuse net that enveloped the animals’ bodies. There was no central processor, no intricate organization, no brain. The next major chapter in the brain’s evolutionary history was a process known as cephalization, in which neurons cluster at one end of an animal, eventually becoming a brain linked to important sensory organs like eyes. Cephalization probably happened several times, and in different ways, in different groups of animals. Within the tiny, simple brains of worms and fish, particular brain regions began to specialize in different functions—one region largely devoted itself to vision, the precursor to our occipital lobe, while another focused on responding to threats, the progenitor of the amygdala. Even before life left the water, animals had evolved brains with much of the same basic neural architecture that we would eventually inherit.

Studying the brain and mind in ignorance of this vast evolutionary tale does not make sense. It would be equivalent to an archaeologist discovering the remains of an enormous tapestry, slicing out a particular figure from the cloth and claiming that he could learn everything he needs to know by examining that figure in isolation. Even if the archaeologist described the figure in exquisite detail, taking it apart thread by thread and sewing it back together, he would remain willfully oblivious of the whole story. In the same way, disregarding the human brain’s history limits psychology and neuroscience to a paltry understanding of our brains and minds.

With regard to our brain’s tumultuous past, evolutionary psychology is primarily concerned with what happened to the human brain during the Paleolithic, between about 2.6 million and ten thousand years ago. Gottlieb is right that evidence of Paleolithic psychology is scant, but it’s not nonexistent. Learning about the brains and behaviors of early humans is a difficult challenge, but not an impossible one [PDF]. By measuring fossil skulls—and creating models of the brains they once held—anthropologists have established that brain size tripled over the course of human evolution. The trend kicks off around 2 million years ago and the swiftest growth occurred between 800,000 and 200,000 years ago during a period of rapid shifts in climate. The National Museum of Natural History has a graph plotting changes in braincase volumes of early humans against changes in the climate. Anthropologists think that early humans with the largest brains adapted most effectively to such a mercurial climate.

Around 100,000 years ago, the human brain largely stopped expanding (and some evidence suggests it has actually shrunk a little since then). What scientists have not yet satisfactorily answered is exactly why the human brain began to swell in the first place and what benefits larger brains offered our ancestors. The most intuitive and tempting explanation is that the expansion of our brains during the Paleolithic paralleled the emergence of more sophisticated intelligence, as partially evidenced by the existing archaeological record of increasingly complex tools and cookware. Learning to cook with fire dramatically improved our ancestors’ diet—it’s much easier to digest and extract calories from soft, cooked foods than from raw, tough foods. In turn, a more nutritious diet likely fueled brain growth. As early human populations increased and spread across the globe, an increasingly diverse social environment would also have demanded a larger and more comlex brain.

One potentially distinct species of hominin called Homo floresiensis, also known as the Hobbit, bucked the trend of bigger brains. Although H. floresiensis went extinct relatively recently, only around 12,000 years ago, it stood just over three feet tall and boasted a brain only half the size of its predecessor, Homo erectus, and one third the size of our modern brains. Yet the remains of H. floresiensis have been discovered alongside evidence of butchery with stone tools and cooking with fire. How, then, do we reconcile the Hobbit’s small brain with evidence of such high intelligence? Is it structure, not size, that matters most? This is exactly the kind of evolutionary puzzle we need to solve to thoroughly understand the human brain and mind. The more we learn about the brains of early humans—and what those brains were capable of—the better we understand our modern minds.

Toward the end of his review, Gottlieb writes: “To confirm any story about how the mind has been shaped, you need (among other things) to determine how people today actually think and behave, and to test rival accounts of how these traits function. Once you have done that, you will, in effect, have finished the job of explaining how the mind works. What life was really like in the Stone Age no longer matters. It doesn’t make any practical difference exactly how our traits became established. All that matters is that they are there.”

Once again, Gottlieb proposes that understanding “how the mind works” is more important than understanding “how the mind has been shaped”—that once you have achieved the former, you need not bother with the latter. One could take a supremely utilitarian approach to the study of the brain and mind, confining oneself to research with explicit practical applications. All Why questions are off the table! We only care about how the mind works. Just explain what happens and move on. No need to think about what any of it means. To be perfectly honest, that sounds unbearably boring to me. More fundamentally, understanding how the mind works and why it works that way are indivisible goals. The human brain’s evolutionary past is not just some cute story we can leave on the shelf if we so please. Every cell in our brains—every moment of our mental lives—is intimately connected to the entire history of life on this planet.

About the Author: Ferris Jabr is an associate editor focusing on neuroscience and psychology. Follow on Twitter @ferrisjabr.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. vinodkumarsehgal 12:30 pm 09/20/2012

    One simple and straight thing : mind is not brain and brain is not mind. As such, even if evolution of brain is understood in proper perspective, this can not lead to automatic understanding of evolution of mind. How neuro scientists are so assured that mind has always evolved and evolved. Could not be there cyclic pattern in the evolution of mind and knowledge?

    Nevertheless the above, mind and brain are intricately linked. A change in the characteristics of brain brings change in mind. But one should not ignore the reverse mechanism also. A conscious change in mind also brings changes in brain’s chemical and electrical character. This itself establishes that mind is not brain and brain is not mind but both work in tandem with each other

    So need shall be to develop better understanding of mind and its interface with brain.

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  2. 2. GreyHare 7:36 pm 09/20/2012

    While evolutionary psychology and similar disciplines have been guilty, at times, of over-reaching themselves, Gottlieb’s article was full of passages that left me scratching my head. In particular, the idea that evolutionary explanations raise more questions, rather than providing final answers, seems very strange- this is they way science works. Theories that explain results give rise to new experiments or opportunities to incorporate field work (ethnographic data, fossil evidence, etc.) to see if the theories still hold. Forming a theory based on an animal model, attempting to confirm it by examining ethnographic data on described hunter-gatherer populations and pre-modern cultures, and then looking for vestiges of that behavior in modern populations (college sophomores or otherwise) is not a ‘just so’ story; it’s a perfectly reasonable synthetic scientific process. Competing theories give rise to new reasons to examine old data, and new tests to look for evidence of the described behaviors in modern populations. If it fails to provide immediate, unambiguous answers, that points as much to the relative youth of the field as to some inevitable failing of evolutionary sociology and psychology.

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  3. 3. jtdwyer 1:30 am 09/21/2012

    What makes us think that absolute brain size is the critical factor in determining intelligence? From braincase analysis, can it be determined whether the Hobbit’s brain was proportionally and structurally similar to modern humans? It seems that brain structural development may be more critical than size in determining intellect. Were pygmy mammoths in some way mentally deficient compared to regular mammoths with much larger brains? Of course I realize these questions can’t be answered, but if pygmy mammoth’s were proportionally less capable than much larger mammoths it would seem they’d have difficulty surviving…

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  4. 4. vinodkumarsehgal 5:54 am 09/21/2012

    Evolutionist scientists trace the history of evolution of brain based upon the weights of skull fossils dating back thousand and million of years ago in the past. here I pose one simple query regarding evolution of brain. Is size of the brain, which may not necessarily correspond to weight of skull, representing nos. of neurons the only indicator of the evolution of brain? Apart from nos. of neuron, are there none of the factors affecting the evolution of brain?

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  5. 5. gs_chandy 9:05 am 09/21/2012

    Indeed, I believe you are correct that it is essential to understand the WHY?s of the evolution of the brain in order to understand the HOW?s about the modern brain’s working! But how to PROVE this? I believe this is extremely difficult to do (perhaps impossible in the conventional ‘prose mode’ of discussion and thinking (which we are using now, for instance). We simply have to argue on the basis of ‘beliefs’ – and get into HUGE (and very complex and difficult) arguments, thereby!

    On the other hand, we could easily construct models showing that the HOW?s and the WHY?s of things are actually inextricable from each other. These models are impossible to explain (or at least more difficult to explain than I am able to do) in this ‘prose mode’ of discussion to which we are limited here. We need to use (I believe) some ‘structural graphics’ for this, going into what I’d call the ‘prose + structural graphics’ (p+sg) mode of discussing and thinking: these structural graphics show precisely the HOW?s and the WHY?s of things. Any high school student will easily understand structural graphics. I’d love to explain ‘structural graphics’ – but I’d have to use graphical models showing the HOW?s and the WHY?s of things.

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  6. 6. gs_chandy 9:12 am 09/21/2012

    Oops – a typo in my ‘pure prose’ argument just presented. The sentence: “I believe this is extremely difficult to do (perhaps impossible in the conventional ‘prose mode’ of discussion and thinking (which we are using now, for instance)” should read, instead, as: “I believe this is extremely difficult to do (perhaps impossible in the conventional ‘prose mode’ of discussion and thinking – which we are using now, for instance)” [NO, this is NOT an instance of the difficulties of 'pure prose' arguments! - just of careless on my part. Sorry about that].

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  7. 7. gs_chandy 9:18 am 09/21/2012

    Notes:
    1. Ferris Jabr has made a very good argument in prose of “Why We Need to Study the Brain’s Evolution in Order to Understand the Modern Mind”
    2. The word “careless” in my 2nd response above should of course read as “carelessness”. — GSC

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  8. 8. Bill_Crofut 7:27 pm 09/22/2012

    Re: “…[O]ne needs to understand how the heart evolved.”

    What is the explanation for how the heart allegedly evolved?

    Clicking on the hyperlink, “how the heart evolved,” leads to the abstract of the paper, “Evolution of the heart from bacteria to man.”* The term, “appearance” is contained in that brief text four times. That conjures up for me the vision of Merlin the magician waving his magic wand. The entire paper is only available at a cost unacceptable to me. However, if the abstract is any indication of what is contained in the body of the paper, it brings to mind the following quote:

    Our willingness to accept scientific claims that are against common sense is the key to an understanding of the real struggle between science and the supernatural. We take the side of science in spite of the patent absurdity of some of its constructs, in spite of its failure to fulfill many of its extravagant promises of health and life, in spite of the tolerance of the scientific community for unsubstantiated just-so stories, because we have a prior commitment, a commitment to materialism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door. The eminent Kant scholar Lewis Beck used to say that anyone who could believe in God could believe in anything. To appeal to an omnipotent deity is to allow that at any moment the regularities of nature may be ruptured, that miracles may happen.
    [Prof. Richard Lewontin. 1997. Billions and Billions of Demons. NY Times Book Reviews: The Demon-Haunted World: Science as a Candle in the Dark by Carl Sagan, Random House, January 9, http://www.drjbloom.com/Public%20files/Lewontin_Review.htm

    * http://www.ncbi.nlm.nih.gov/pubmed/16093481

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  9. 9. Semantics 2:39 am 10/6/2012

    Fantastic article to read, i like this part:”Consciousness, self-awareness, complex emotions, language, creativity—if you want to truly understand these aspects of mind, you must understand when and why they first evolved. To do that, you must understand how the brain has changed over time”.
    The basic principle of it reads to me like this; in order to understand an object, there are indicators, which need to be translated by the human mind;shape,size,substance,function,performance and benefit. Historically it usually meant is it edible, is it enjoyable, is it beneficial.

    If that is the basis for reason, then how does the current world market driven economy, and the material pursuit of objects people spend their money on, reflect the theory that the mind is a slave to evolutionary process. It is supported by the basic molecular building blocks, but the thinking of the mind is at another level. For example a computer program is not
    limited to the type of keyboard that the user happens to inherited.

    Great blog, let’s all think more.

    Link to this
  10. 10. Dalton 7:14 pm 04/16/2013

    In my studies and experience, virtually every discipline has some contribution to make to the understanding of both brain and mind. As for the impact of evolution on our understanding, the implications ebb and flow for evolution tends towards the greatest diversity possible. I believe that what evolution may have to contribute to understanding the brain and mind must be assessed in the context of the era involved. The history of species, organs, and anatomical prowess has been under the influence of varied environmental conditions since life began on this planet. While it may be true that many anatomical and mental features have been conserved over the eons, I would say that it is a safe bet to assume they have all been subject to changes that make even educated guess work somewhat fashionable. I believe the key to any theories concerning the evolutionary impact on our understanding lies in how useful and effective it may be in creating a successful emulation of the brain and its operation.

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  11. 11. JasonKnighte 8:33 pm 01/8/2014

    It sounds like it is a very interesting study, I wander what kinds of secrets of the mind they will unlock. I think that there is a lot to be learned.

    Jason.
    http://professional-siding.com/siding.php

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