Tag Archives: Animal Rights

Are Pigs Really Like People?

We hear this all the time. Pig physiology is like people physiology. Pigs and humans have the same immune system, same digestive system, get the same diseases. Pigs are smart like people are smart. Pigs are smarter than dogs. And so on. Ask a faunal expert in archaeology or a human paleoanatomist: Pig teeth are notoriously like human teeth, when fragmented. Chances are most of these alleged similarities are overstated, or are simply because we are all mammals. Some are because we happen to have similar diets (see below). None of these similarities occur because of a shared common ancestor or because we are related to pigs evolutionarily, though there are people who claim that humans are actually chimpanzee-pig hybrids. We aren’t.

But what if it is true that pigs and humans ended up being very similar in a lot of ways? What if many of the traits we attribute to our own species, but that are rare among non-human animals, are found in pigs? Well, before addressing that question, it is appropriate to find out if the underlying assumption has any merit at all. A new study by Lori Marino and Christina Colvin, “Thinking Pigs: A Comparative Review of Cognition, Emotion, and Personality in Sus domesticus,” published in the International Journal of Comparative Psychology, provides a starting point.

There are two things you need to know about this study. First, it is a review, looking at a large number of prior studies of pigs. It is not new research and it is not a critical meta-study of the type we usually see in health sciences. The various studies reviewed are not uniformly evaluated and there is no attempt at assessing the likelihood that any particular result is valid. That is not the intent of the study, which is why it is called a review and not a meta-study, I assume. But such reviews have value because they put a wide range of literature in one place which forms a starting point for other research. The second thing you need to know is that the authors are heavily invested in what we loosely call “animal rights,” as members of the Kimmela Center for Animal Advocacy and the Someone Project (Farm Sanctuary). From this we can guess that a paper that seems to show pigs-human similarities would ultimately be used for advocating for better treatment for domestic pigs, which are raised almost entirely for meat. There is nothing wrong with that, but it should be noted.

In a moment I’ll run down the interesting findings on pig behavior, but first I want to outline the larger context of what such results may mean. The paper itself does not make an interpretive error about pig behavior and cognition, but there is a quote in the press release that I’m afraid will lead to such an error, and I want to address this. The quote from the press release is:

Dr. Marino explains that “We have shown that pigs share a number of cognitive capacities with other highly intelligent species such as dogs, chimpanzees, elephants, dolphins, and even humans. There is good scientific evidence to suggest we need to rethink our overall relationship to them.”

What does that mean? In particular, what does the word “relationship” mean? In a behavioral comparative study, “relationship” almost always refers to the evolutionary structure of the traits being observed. For example, consider the question of self awareness, as often tested with the Gallup Test, which measures Mirror Self Recognition (MSR). If a sufficient sample of test animals, when looking in a mirror almost always perceive a conspecific, then that species is considered to not have MSR. If most, or even many, individuals see themselves, then that species is said to have MSR, a kind of self awareness that is linked to a number of important other cognitive capacities.

Humans have MSR. So, do our nearest relatives, the chimps have it? Do the other apes have it? Other primates? Is this a general mammalian capacity or is it a special-snowflake trait of our own species? It turns out that all the great apes have MSR, but primates generally do not. It may or may not appear among other primates (mostly not). So MSR reflects something that evolved, likely, in the common ancestor of humans and all the other apes. So, the relationship among the primates with respect to MSR, phylogenetically, is that MSR is a shared derived trait of the living apes, having evolved in or prior to that clade’s last common ancestor.

But we also see MSR in other species including, for example, elephants. The presents of MSR in elephants does not mean MSR is a widespread trait that humans and elephants both have because a common ancestor hat it. Rather, in some cases (the great apes), MSR is clustered in a set of closely related species because it evolved in their ancestor, and at the same time, it appears here and there among other species for either similar reasons, or perhaps even for different reasons.

This is why the word “relationship” is so important in this kind of research.

It is clear that Dr. Marino does not use the word “relationship” in that press release to mean that pigs and humans share interesting cognitive and behavioral traits because of common ancestry, but rather, I assume, the implication is that we may want to think harder about how we treat pigs because they are a bit like us.

One could argue, of course, that a species that is a lot like us for reasons other than shared evolutionary history is a bit spooky. Uncanny valley spooky. Or, one could argue that such a species is amazing and wonderful, because we humans know we are amazing and wonderful so they should be too. Indeed one could argue, as I have elsewhere, that similarity due to shared ancestry and similarity due to evolutionary convergence are separate and distinct factors in how we ultimately define our relationship to other species, how we treat them, what we do or not do with them. The important thing here, that I want to emphasize, is that human-pig similarity is not the same thing as human-chimp similarity. Both are important but they are different and should not be conflated. I honestly don’t think the paper’s authors are conflating them, but I guarantee that if this paper gets picked up by the press, conflation will happen. I’ll come back to a related topic at the end of this essay.

I’ve been interested in pigs for a long time. I’ve had a lot of interactions with wild pigs while working in Africa, both on the savanna and the rain forest. One of the more cosmopolitain species, an outlier because it is a large animal, is the bush pig. Bush pigs live in very arid environments as well as the deepest and darkest rain forests. There are more specialized pigs as well. The forest pig lives pretty much only in the forest, and the warthog does not, preferring savanna and somewhat dry habitats. Among the African species, the bush pig is most like the presumed wild form of the domestic pig, which for its part lived across a very large geographical area (Eurasia) and in a wide range of habitats. I would not be surprised if their populations overlapped at some times in the past. This is interesting because it is very likely that some of the traits reviewed by Marino and Colvin allow wild pigs to live in such a wide range of habitats. There are not many large animals that have such a cosmopolitain distribution. Pigs, elephants, humans, a few others. Things that know something about mirrors. Coincidence? Probably not.

Pigs (Sus domesticus and its wild form) have an interesting cultural history in the west. During more ancient times, i.e., the Greek and Roman classical ages, pigs were probably very commonly raised and incorporated in high culture. One of Hercules seven challenges was to mess with a giant boar. Pigs are represented in ancient art and iconography as noble, or important, and generally, with the same level of importance as cattle.

Then something went off for the pigs. Today, two of the major Abrahamic religions view pigs as “unclean.” Ironically, this cultural insult is good for the pigs, because it also takes them right off the menu. In modern Western culture, most pigs are viewed as muddy, dirty, squealing, less than desirable forms. Bad guys are often depicted as pigs. One in three pigs don’t understand their main predator, the wolf. There are important rare exceptions but they are striking because they are exceptions. This denigration of pigs in the West is not found globally, and in Asia pigs have always been cool, sometimes revered, always consumed.

I should note that I learned a lot of this stuff about pigs working with my good fiend and former student Melanie Fillios, who did her thesis (published here) on complexity in Bronze Age Greece, and that involved looking at the role of pigs in the urban and rural economies. At that time Melanie and I looked at the comparative behavioral and physical biology of cattle vs. pigs. This turns out to be very interesting. If you started out with a two thousand pounds of pig and two thousand pounds of cattle, and raised them as fast as you could to increase herd size, in a decade you would have a large herd of cattle, but if you had been raising pigs, you’d have enough pigs to cover the earth in a layer of them nine miles thick. OK, honesty, I just made those numbers up, but you get the idea; Pigs can reproduce more than once a year, have large litters, come to maturity very quickly, and grow really fast. Cattle don’t reproduce as fast, grow slower, take longer to reach maturity, and have only one calf at a time.

On the other hand, if you have cattle, you also have, potentially, milk (and all that provides), hoof and horn (important in ancient economies) and maybe better quality leather. I’ll add this for completeness: Goats are basically small cows with respect to these parameters.

Now, having said all that, I’ll summarize the material in the paper so you can learn how amazing pigs are. From the press release:

  • have excellent long-term memories;
  • are whizzes with mazes and other tests requiring location of desired objects;
  • can comprehend a simple symbolic language and can learn complex combinations of symbols for actions and objects;
  • love to play and engage in mock fighting with each other, similar to play in dogs and other mammals;
  • live in complex social communities where they keep track of individuals and learn from one another;
  • cooperate with one another and show signs of Machiavellian intelligence such as perspective-taking and tactical deception;
  • can manipulate a joystick to move an on-screen cursor, a capacity they share with chimpanzees;
  • can use a mirror to find hidden food;
  • exhibit a form of empathy when witnessing the same emotion in another individual.
  • Pigs are very snout oriented. They have lots of nerve endings in their snouts and can use the information they get from this tactile organ for social interactions and finding food. They can tell things apart very easily, learn new classifications, and remember objects and things about them. This makes sense for an animal that forages at the ground surface, including underground, for a very wide range of food types.

    One of the cool human traits we often look for in other animals is the ability to time travel. We don’t actually travel in time, but in our minds, we can put ourselves in other places and other times, and run scenarios. Some of the basic capacities required to do this include a sense of lengths of times for future events or situations, and an understanding of these differences. Pigs can learn that of two enclosures they can choose from, one will let them out sooner than the other one, for example.

    Pigs have excellent spatial memory and can learn where things are and how to find them. They can do mazes as well as other animals that have been tested in this area.

    Pigs have individual personalities, to a large degree, and can discriminate among other individuals and recognize certain aspects of their mental state. This applies to other individual pigs as well as individuals of other species (like humans).

    Pigs have a certain degree of Machiavellian intelligence. This is rare in the non-human animal world. If a pig has the foraging pattern for a given area down well, and a potential competitor pig is introduced, the knowledgable pig will play dumb about finding food. They don’t have MSR but they can use mirrors to find food.

    Now, back to the evolutionary context. I’ve already hinted about this a few times. Pigs and humans share their cosmopolitain distribution, with large geographic ranges and a diversity of habitats. We also share a diverse diet. But, it goes beyond that, and you probably know that I’ve argued this before. Pigs are root eaters, as are humans, and this feature of our diet is probably key in our evolutionary history. From my paper, with Richard Wrangham, on this topic:

    We propose that a key change in the evolution of hominids from the last common ancestor shared with chimpanzees was the substitution of plant underground storage organs (USOs) for herbaceous vegetation as fallback foods. Four kinds of evidence support this hypothesis: (1) dental and masticatory adaptations of hominids in comparison with the African apes; (2) changes in australopith dentition in the fossil record; (3) paleoecological evidence for the expansion of USO-rich habitats in the late Miocene; and (4) the co-occurrence of hominid fossils with root-eating rodents. We suggest that some of the patterning in the early hominid fossil record, such as the existence of gracile and robust australopiths, may be understood in reference to this adaptive shift in the use of fallback foods. Our hypothesis implicates fallback foods as a critical limiting factor with far-reaching evolutionary e?ects. This complements the more common focus on adaptations to preferred foods, such as fruit and meat, in hominid evolution.

    Pigs and humans actually share dental and chewing adaptations adapted, in part, for root eating. The pig’s snout and the human’s digging stick have been suggested (see the paper) as parallelisms. And so on.

    Yes, humans and pigs share an interesting evolutionary relationship, with many of our traits being held in common. But this is not because of shared ancestry, but rather, because of similar adaptive change, independent, in our evolutionary history. This whole root eating thing arose because of a global shift from forests to mixed woodland and otherwise open habitats, which in turn encouraged the evolution of underground storage organs among many species of plants, which in turn caused the rise of a number of above ground root eaters, animals that live above the surface but dig. Not many, but some. Pigs, us, and a few others.

    That does not make us kin, but it does make us kindred.

    Many Duluth Zoo Animals Dead In Floods

    Duluth, a second tier Minnesota city on Lake Superior, has been flooding. This is a little unusual; heavy rains following a period of saturation have caused a local river that is usually not even heard of to grow very large and cause flooding that a lot of people haven’t seen before.

    The polar bear and the seal were able to leave their enclosures in the high water. The bear was darted and is safely put away somewhere, the seal is said to have taken a stroll around the neighborhood. But the barn animals, apparently including cattle, ovicaprids, and donkey have all perished in the flood.

    This raises an interesting point. The flooding risk to a given piece of land is pretty much known in the US for everywhere. It seems like it would be a fairly easy task to determine if animal enclosures or other areas in a zoo are at risk of being flooded like this, and then to redesign to allow for animals to escape to somewhere. One would think that his would be a responsibility automatically addressed by Zoo managers. I’m fairly sure the federal governing body for Zoos is, at least in part, the USDA. Perhaps they have an opinion on this.

    In this particular case, it seems (subject to revision) that a particular culvert had become blocked with debris, and thus water backed up into the zoo. Eventually, the culvert was totally washed out which presumably would have allowed flood water to recede. It is possible to re-engineer culverts to avoid this sort of thing from happening. An assessment of the likelihood of flooding here may well have led to such a fix prior to the incident.

    Should existing zoos be assessed for future flood risk?

    Here’s a local news story.

    Yes, the animals were contained within the property, but not necessarily alive. My sense is that he already knows the state of the animals but is letting the Zoo folks handle the news.

    And yes, the “Highway 61” mentioned in the news is, indeed this one:

    Photo of bear by clairity

    Animal Rights and Human Needs: Foundations of the debate (Part III)

    …. Continued ….

    So, what rights to what animals get?

    When Charlton Heston’s character in Planet of the Apes came across that great edifice of Western Civilization and realized that the old Orangutan was right … humans are fundamentally destructive of themselves and their near relatives … he replicated in the fictional future what Louis and Mary Leakey did when they came across the skull of Zinjanthropus at Olduvai Gorge, in the 1950s, at a spot now memorialized by the famous Olduvai Plinth. Well the Leakeys thought they were looking at a human ancestor at the time, and therefore missed the point. What they were looking at, most likely, was somebody’s dinner. Dinner consisting of a member of a species of our nearest living relative, on an archaeological site generated by many different effects including the activity of what actually was our direct ancestor, Homo erectus.

    To be fair, we can’t be sure if Olduvai Hominid #5 was eaten by Homo erectus or by a leopard or something. But, it represented a species that disappeared when Homo erectus appeared. For several million years, at any one point in time, a diversity of hominid species lived in Africa, like we see today in the diversity of antelopes. Then Homo erectus came along and thereafter the diversity was suddenly reduced and generally maintained to one species almost everywhere, two species here and there.

    My point is this: It is not entirely unreasonable to view the question of what humans can do to other species with suspicion. This would be the same kind of suspicion that a parole board would level against an inmate asking for release. We are a species with a record, and we are asking the question: What ways shall we allow this species, already tried and convicted of serial speciescide, to interact with other animal species? We are a level five extinctionator asking to move into a neighborhood with lots of vulnerable species like chimps and polar bears. And we’ve done little to earn trust. One could make the argument that the assumption that we can kill any animal we want to should not be the starting point for this discussion. Perhaps the assumption that we should not use any animals in research or cuisine is a more appropriate starting point given our record.

    To summarize so far:

    1) There is no way to satisfy all parties in this discussion, so every party that wants to be part of it has to be open to final solutions that are different then, to them, ideal.

    2) Parties in this discussion should avoid the presumption of wrongness and nefarious intent on the part of other parties.

    3) The fundamental assumptions often made in this discussion are probably flawed and the realities are probably mostly quite arbitrary.

    4) There is a reasonable argument for a phylogenetic approach to assigning “rights” to non-human animals.

    5) Humans need to be a little more humble in their approach to this issue, given their record.


    My strong preference is that chimpanzees and other great apes are given, essentially, the same level of protection in relation to research as humans are given. Certainly, when it comes to other invasive or damaging but non-research related activities, it is fairly easy to see how this can be carried out, at least in relation to policy: No hunting, no habitat destruction. When it comes to research, however, this may be more difficult. For the vast majority of research projects, apes simply should not be used. But people have argued that certain critically important research that has saved human lives has been done on chimps (typically) and had that not been done, there would be more human death and misery, etc. Those who believe that the Great Apes should not be used in research may well respond “tough luck, those humans simply have to suffer, as though the apes never existed.” Others would accept that some research should be done despite the fact that we really don’t want to.

    Bring all the ideas to the table and remember that you are not going to get the exact solution you want. I believe that there is no way to disconnect the specifics of a particular (potential or real) research program and the questions at hand. Humans can be (and are) used in research. If so, then so can apes be used in research, but not in just any way one feels like doing. One can say post-hoc that a certain medical advance used ape research, but did it really? And is it the case that the actual research that was done, in terms of sample size and methods, was necessary, or were there alternatives that were not pursued because it was considered acceptable to treat the Great Apes in a particular way that may not be acceptable under a modernized policy?

    My feeling is that research on the Great Apes may be justifiable, but not a priori, and certainly not a priori on the basis of presumed successes of the past. Each and every proposed case needs to be evaluated to a degree much greater than any of this research has been evaluated to date. No more secrecy, no more vagueness (at the moment we are not even sure exactly how many chimps are in research facilities). No more dicking around. Just honest and open evaluation. And in the end, I would think almost no research using Great Apes would be considered acceptable.

    (See also: Are Pigs Really Like Humans?)

    I should also mention an exception to the phylogenetic guideline that gives the Great Apes a special place: Dolphins and other whales. It may well be that dolphins, which have evolved smart brains, what appears very much to be actual symbolic capacities, curiosity, apparent sentience (not just something that looks like sentience) and a complex social system that makes chimps look simple, should be fully protected. Personally, I’m for ending all whale harvesting, not because of any humanness but for the same reason I don’t think we should hunt aardwolves or rhinos. We’ve done enough, just leave them alone. There will be exceptions, we’ll deal with those as they come along. But as a rule, the conservation of these species is paramount. Since the whales are rarely used in human disease related research, they are in a different position that the Great Apes in this discussion, and should probably be addressed separately.