I’m disappointed in the lack of research applied to this conversation. Many people are referring to “modern science”, “decades of research”, and “scientific studies” but nobody has cited anything specifically other than a New York Times article which doesn’t even cite the research that it is reporting on, so we can’t investigate for ourselves to judge the reliability of these sources. It is true that I did not cite any research myself when I first posted my opinion on this matter, but I also did not claim that my opinion stemmed from some mysterious research paper. It was my opinion based on my very limited prior knowledge of neurology and personal experiences. But with the conversation going on this long and becoming so heated, we should be stepping beyond opinion and personal experience to support our arguments at this point. So I have decided to look into the topic on my own and share with you the most relevant and recent sources that I could find. To be clear; I did not conduct my research in such a way as to support my opinion, but rather to shed light on all sides of this discussion. I have excluded findings that seemed somewhat irrelevant, outdated, or vague, but nothing has been excluded due to disagreement with my own opinion.
Firstly, regarding the evolution of the brain and similarities between the brains of humans and other animals, the most straightforward(though least thorough) source I have is my vertebrate biology textbook. For all those with a library card:
Kardong, Kenneth V. "The Nervous System."*Vertebrates: Comparative Anatomy, Function, Evolution. 6th ed. New York: McGraw-Hill, 2012. 652-66. Print.
While there are homologs of key brain structures across all vertebrates, the capacity and function of these homologs varies between different kinds of animals according to their needs and modes of living. These differences correspond to significant differences in behavior and bodily functions. The brains of reptiles are drastically different from animals such as birds and mammals that are widely accepted as being capable of affection. Furthermore, there are several structures present in birds and mammals which do not have any homologs in reptiles, not all of which have known functions. This does not shed any light on our debate, but I felt the need to counter the idea that “It is now known that brain structure and chemistry is identical in all vertebrates from the lamprey to humans.” as it was used as a supporting argument within this discussion. Brain structure, and even cell class diversity, varies substantially between species even within the same order. More in-depth information on brain variation can be found here:
Northcutt, R. G. "Understanding Vertebrate Brain Evolution."*Integrative and Comparative Biology*42.4 (2002): 743-56. Web.
The study is a bit old, but goes into specific differences in cell classes and general structure. There is no information here tying these differences to the presence or absence of affection, but with the incredible differences between reptile and mammalian brains, I see no reason why one should assume the same responses are happening in reptiles as in mammals.
Here’s an interesting discussion of the evolution of brains in general:
Barbieri, Marcello. "Origin and Evolution of the Brain."*Biosemiotics*4.3 (2011): 369-99. Web.
Barbieri draws on numerous sources dated as early as 1943 and as late as 2010. I did not assess these sources, as there were quite a lot, but I did not see any red flags indicating anything may have been taken out of context or from a non-reputable source. The article goes into great detail about how different aspects of the central nervous system came to be. All aspects of the brain and its functions can be related to evolutionary theory, and strong development of specific neurological traits has been linked to various evolutionary advantages. This is quite relevant to the question that has come up repeatedly here: How would love and affection benefit snakes as a species? From an evolutionary perspective, it is unlikely that this trait would be retained since the majority of snakes are reproductively successful without any apparent form of affection. However, it is also made clear that the concepts of thought and mind are so poorly understood that we cannot clearly define what comprises the mind of other species.
This is my favorite find out of them all:
Ledoux, Joseph. "Rethinking the Emotional Brain."*Neuron*73.4 (2012): 653-76. Web.
It’s quite a lengthy paper, but it’s a great read and explores all aspects of the concept of emotion, how it works, and various theories regarding its purpose and evolution. They did up all their references in blue so it is quite clear where their ideas are coming from if you wish to explore any of them yourself. One section that really popped out to me was this:
Quote:
And given that some of the neural
mechanisms involved in conscious representations may be
different in humans and other animals, we should be cautious
in assuming that the subjectively experienced phenomena that
humans label as feelings are experienced by other animals
when they engage in behaviors that have some similarity to
human emotional behavior. In short, if the circuits that give rise
to conscious representations are different in two species, we
cannot use behavioral similarity to argue for similarity of
conscious feelings functionally. These observations add neuro-
biological substance to the point famously argued by the
philosopher Thomas Nagel. He proposed that only a bat can
experience the world like a bat, and only a human can experi-
ence the world like a human (Nagel, 1974). We should resist
the inclination to apply our introspections to other species.
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Which is later expanded upon with this:
Quote:
We will
never know what an animal feels. But if we can find neural corre-
lates of conscious feelings in humans (and distinguish them from
correlates of unconscious emotional computations in survival
circuits), and show that similar correlates exists in homologous
brain regions in animals, then some basis for
speculating
about
animal feelings and their nature would exist. While such specula-
tions would be empirically based, they would nevertheless
remain speculations.
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With 9 pages of citations backing up this paper, many of which are quite recent, its standpoint is certainly compelling. Ledoux has granted that we simply do not know enough about non-human brains in general to determine with certainty whether any animal besides humans feels human-like emotions. However, he indicates that because the structure and makeup of the brains of non-mammals is so drastically different from that of humans, we cannot assume that they feel or interpret anything in any similar fashion to the way we do. He has suggested that it is possible that other animals, even ones with extremely primitive central nervous systems such as invertebrates, may be capable of extremely diverse ranges of mental activity including human-like emotion or even experiences beyond human capabilities, but through means that are completely different from human means of emotion.
This is not a scientific study, but it’s a very nice observation of a mother Arizona black rattlesnake caring for her young.
SocialSnakes: A day in the life of a rattlesnake family
Whether you consider this behavior in itself to be a show of affection is up to you(I personally have no clue where to draw the line between maternal instinct and familial affection, if there is a line at all, since affection is such a vague concept), but it does at least show that some degree of social affinity exists among snakes. Most snakes do not care for their young and would even eat their own, though, so it’s impossible to say how prevalent the genetic and physiological basis for this behavior might be throughout suborder Serpentes.
Expanding on the question of the extent of social behavior in reptiles, we have this brief paper:
Doody, Sean, J, Gordon M. Burghardt, and Vladimir Dinets. "Breaking the Social–Non-social Dichotomy: A Role for Reptiles in Vertebrate Social Behavior Research?"*International Journal of Behavioural Biology: Ethology*119 (2013): 95-103. Web.
Summarizing various observances of social behavior in reptiles, including group coordinated hunting in sea snakes. Most of the examples described are not relateable to mammals, for example the ability of sea turtles to detect and respond to the activity of their clutchmates before hatching, so it is difficult to assess them as “social” behavior, but indeed we can expect reptilian social dynamics to be quite different from that of mammals.
What I’d really like to see is a study monitoring the brain activity of rattlesnakes carrying out maternal care tasks and comparing it to brain activity during activities such as “kissing” when interacting with handlers. Would the same regions of the brain light up? How would the results then compare to acts of affection in birds or mammals? But the biggest question is; who would pay for such research?
I personally do not see things any differently after having done my research. I have certainly gained new insight into the potential for social motives and a wide range of feelings and emotions in reptiles, but I still do not see a reason to believe that snakes are affectionate. I would not say it’s entirely impossible, but it is something that does not seem to make sense in light of the evidence currently available. The desire to care for and protect a member of another species does not seem like a trait that would benefit snakes in the progress of their evolution. Keep in mind that although mammals and birds arose after reptiles, from common ancestry, they did not arise from extant lineages of reptiles. The reptiles we see around us today are entirely distinct from the common ancestors shared by birds and mammals.
On a side note, if anyone has access to this paper:
A.B. Butler, R.M.J. Cotterill, Mammalian and avian neuroanatomy and
the question of consciousness in birds, Biol. Bull. 211 (2006) 106–
127.
I’d be very interested to hear about it. Apparently it describes the role of the limbic territory of the striatum, which is not present in reptiles, and compares its role in birds and mammals.(it was cited in another paper I read, which I did not include here due to its vagueness) I feel a better understanding of the function of the limbic territory would contribute to this discussion.
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