I have seen some people claim that animal activists should primarily be concerned with certain groups of numerous vertebrates, such as chickens and fish, whereas we should not be concerned much, if at all, with insects and other small invertebrates. (See e.g. here.) I think there are indeed good arguments in favor of emphasizing chickens and fish in animal advocacy, yet I think those same arguments tend to support a strong emphasis on helping insects as well. My aim in this post is to argue that we have compelling reasons to include insects and other small vertebrates in animal advocacy.
- A simplistic sequence argument: Smaller beings in increasingly large numbers
- Invertebrate vs. vertebrate nervous systems
- Objection based on appalling treatment
- Potential biases
- Other reasons to focus more on small invertebrates
- My own view on strategy in brief
- Final clarification: Numbers-based arguments need not assume that large amounts of mild suffering can be worse than extreme suffering
A simplistic sequence argument: Smaller beings in increasingly large numbers
As a preliminary motivation for the discussion, it may be helpful to consider the sequence below.
I should first of all clarify what I am not claiming in light of the following sequence. I am not making any claims about the moral relevance of the neuron counts of individual beings or groups of beings (that is a complicated issue that defies simple answers). Nor am I claiming that we should focus mostly on helping beings such as land arthropods and nematodes. The claim I want to advance is a much weaker one, namely that, in light of the sequence below, it is hardly obvious that we should focus mostly on helping chickens or fish.
At any given time, there are roughly:
- 780 million farmed pigs, with an estimated average neuron count of 2.2 billion. Total neuron count: ~1.7 * 10^18.
- 33 billion farmed chickens, with an estimated average neuron count of 200 million. Total neuron count: ~6.6 * 10^18.
- 10^15 fish (the vast majority of whom are wild fish), with an estimated average neuron count of 1 million neurons (this number lies between the estimated neuron count of a larval zebrafish and an adult zebrafish; note that there is great uncertainty in all these estimates). Total neuron count: ~10^21. It is estimated that humanity kills more than a trillion fish a year, and if we assume that they likewise have an average neuron count of around 1 million neurons, the total neuron count of these beings is ~10^18.
- 10^19 land arthropods, with an estimated average neuron count of 15,000 neurons (some insects have brains with more than a million neurons, but most arthropods appear to have considerably fewer neurons). Total neuron count: ~1.5*10^23. If humanity kills roughly the same proportion of land arthropods as the proportion of fish that we kill (e.g. through insecticides and insect farming), then the total neuron count of the land arthropods we kill is ~10^20.
- 10^21 nematodes, with an estimated average neuron count of 300 neurons. Total neuron count: ~3 * 10^23.
Why stop at chickens or fish?
The main argument that supports a strong emphasis on chickens or fish is presumably their large numbers (as well as their poor treatment, which I discuss below). Yet the numbers-based argument that supports a strong emphasis on chickens and fish could potentially also support a strong emphasis on small invertebrates such as insects. It is thus not clear why we should place a strict boundary right below chickens or fish beyond which this numbers-based argument no longer applies. After all, each step of this sequence entails a similar pattern in terms of crude numbers: we have individual beings who on average have 1-3 orders of magnitude fewer neurons yet who are 1-5 orders of magnitude more numerous than the beings in the previous step.
Invertebrate vs. vertebrate nervous systems
A defense that one could give in favor of placing a relatively strict boundary below fish is that we here go from vertebrates to invertebrates, and we can be significantly less sure that invertebrates suffer compared to vertebrates.
Perhaps this defense has some force. But how much? Our confidence that the beings in this sequence have the capacity to suffer should arguably decrease at least somewhat in each successive step, yet should the decrease in confidence from fish to insects really be that much bigger than in the previous steps?
Based on the knowledge that we ourselves can suffer, one might think that a group of beings’ phylogenetic distance from us (i.e. how distantly related they are to us) can provide a tentative prior as to whether those beings can suffer, and regarding how big a jump in confidence we should make for different kinds of beings. Yet phylogenetic distance per se arguably does not support a substantially greater decrease in confidence in the step from fish to insects compared to the previous steps in the sequence above.
The last common ancestor of humans and insects appears to have lived around 575 million years ago, whereas the last common ancestor of humans and fish lived around 400-485 million years ago (depending on the species of fish; around 420-460 million years for the most numerous fish). By comparison, the last common ancestor of humans and chickens lived around 300 million years ago, while the last common ancestor of humans and pigs lived around 100-125 million years ago.
Thus, when we look at different beings’ phylogenetic distance from humans in these temporal terms, it does not seem that the step between fish and insects (in the sequence above) is much larger than the step between fish and chickens or between chickens and pigs. In each case, the increase in the “distance” appears to be something like 100-200 million years.
Behavioral and neurological evidence
Of course, “phylogenetic distance from humans” does not represent strong evidence as to whether a group of beings has the capacity to suffer. After all, humans are more closely related to starfish (~100 neurons) than to octopuses (~500 million neurons), and we have much stronger reasons to think that the latter can suffer, based on behavioral and neurological evidence (cf. the Cambridge Declaration on Consciousness).
Does such behavioral and neurological evidence support a uniquely sharp drop in confidence regarding insect sentience compared to fish sentience? Arguably not, as there is mounting evidence of pain in (small) invertebrates, both in terms of behavioral and neuroscientific evidence. Additionally, there are various commonalities in the respective structures and developments of arthropod and vertebrate brains.
In light of this evidence, it seems that a sharp drop in confidence regarding pain in insects (versus pain in fish) requires a justification.
Nematodes and extended sequences
I believe that a stronger decrease in confidence is warranted when comparing arthropods and nematodes, for a variety of reasons: the nematode nervous system consists primarily of a so-called nerve ring, which is quite distinct from the brains of arthropods, and unlike the neurons of arthropods (and other animals), nematode neurons do not have action potentials or orthologs of sodium-channels (e.g. Nav1 and Nav2), which appear to play critical roles to pain signaling in other animals.
However, the evidence of pain in nematodes should not be understated either. The probability of pain in nematodes still seems non-negligible, and it arguably justifies substantial concern for (the risk of) nematode pain, even if it does not overall warrant a similarly strong concern and priority as does the suffering of chickens, fish, and arthropods.
This discussion also hints at why the sequence argument above need not imply that we should primarily focus on risks of suffering in bacteria or atoms, as one may reasonably hold that the probability of such suffering decreases by a greater rate than the number of the purported sufferers increases in such extended sequences.
Objection based on appalling treatment
Another reason one could give in favor of focusing on chickens and fish is that they are treated in particularly appalling ways, e.g. they are often crammed in extremely small spaces and killed in horrific ways. I agree that humanity’s abhorrent treatment of chickens and fish is a strong additional reason to prioritize helping them. Yet it seems that this same argument also favors a focus on insects.
After all, humanity poisons vast numbers of insects with insecticides that may cause intensely painful deaths, and in various insect farming practices — which are sadly growing — insects are commonly boiled, fried, or roasted alive. These practices seem no less cruel and appalling than the ways in which we treat and kill chickens and fish.
There are many reasons to expect that we are biased against giving adequate moral consideration to small invertebrates such as insects (in addition to our general speciesist bias). The four plausible biases listed below are by no means exhaustive.
It is highly inconvenient if insects can feel pain, as it would imply that 1) we should be concerned about far more beings, which greatly complicates our ethical and strategic considerations (compared to if we just focused on vertebrates); 2) the extent of pain and suffering in the world is far greater than we would otherwise have thought, which may be a painful conclusion to accept; and 3) we should take far greater care not to harm insects in our everyday lives. All these inconveniences likely motivate us to conclude that insects are not sentient or that they are not that important in the bigger picture.
Insects tend to be rather small, even compared to fish, which might make us reluctant to grant them moral consideration. In other words, our intuitions plausibly display a general sizeist bias. As a case in point, ants have more than twice as many neurons as lobsters, and there does not seem to be any clear reason to think that ants are less able to feel pain than are lobsters. Yet ants are obviously much smaller than lobsters, which may explain why people seem to show considerably more concern for lobsters than for ants, and why the number of people who believe that lobsters can feel pain (more than 80 percent in a UK survey) is significantly larger than the number of people who believe that ants can feel pain (around 56 percent). Of course, this pattern may also be partially explained by the inconvenience bias, since the acceptance of pain in lobsters seems less inconvenient than does the acceptance of pain in ants; but size likely still plays a significant role. (See also Vinding, 2015, “A Short Note on Insects”.)
Disgust and fear reflexes
It seems that many people have strong disgust reactions to (at least many) small invertebrates, such as cockroaches, maggots, and spiders. Some people may also feel fear toward these animals, or at least feel that they are nuisance. Gut reactions of this kind may well influence our moral evaluations of small invertebrates in general, even though they ideally should not.
Momentum/status quo bias
The animal movement has not historically focused on invertebrates, and hence there is little momentum in favor of focusing on their plight. That is, our status quo bias seems to favor a focus on helping the vertebrates whom the animal movement have traditionally focused on. To be sure, status quo bias also works against concern for fish and chickens to some degree (which is worth controlling for as well), yet chickens and fish have still received considerably more focus from the animal movement, and hence status quo bias likely negates concern for insects to an even stronger extent.
These biases should give us pause when we are tempted to reflexively dismiss the suffering of small invertebrates.
Other reasons to focus more on small invertebrates
In addition to the large number of arthropods and the evidence for arthropod pain, what other reasons might support a greater focus on small invertebrates?
An obvious reason is the neglect of these beings. As hinted in the previous section, a focus on helping small invertebrates has little historical momentum, and it is still extremely neglected in the broader animal movement today. This seems to me a fairly strong reason to focus more on invertebrates on the margin, or at the very least to firmly include invertebrates in one’s advocacy.
Opening people’s eyes to the extent of suffering and harmful decisions
Another, perhaps less obvious reason is that concern for smaller beings such as insects might help reduce risks of astronomical suffering. This claim should immediately raise some concerns about suspicious convergence, and as I have argued elsewhere, there is indeed a real risk that expanding the moral circle could increase rather than reduce future suffering. Partly for this reason, it might be better to promote a deeper concern for suffering than to promote wider moral circles (see also Vinding, 2020, ch. 12).
Yet that being said, I also think there is a sense in which wider moral circles can help promote a deeper concern for suffering, and not least give people a more realistic picture of the extent of suffering in the world. Simply put, a moral outlook that includes other vertebrates besides humans will see far more severe suffering and struggle in the world, and a perspective that also includes invertebrates will see even more suffering still. Indeed, not only does such an outlook open one’s eyes to more existing suffering, but it may also open one’s eyes (more fully) to humanity’s capacity to ignore suffering and to make decisions that actively increase it, even today.
Risks of spreading invertebrates to space: Beings at uniquely high risk of suffering due to human space expansion
Another way in which greater concern for invertebrate suffering might reduce risks of astronomical suffering is that small invertebrates seem to be among the animals who are most likely to be sent into space on a large scale in the future (e.g. because they may survive better in extreme environments). Indeed some invertebrates — including fruit flies, crickets, and wasps — have already been sent into space, and some tardigrades were even sent to the moon (though the spacecraft crashed and probably none survived). Hence, the risk of spreading animals to space plausibly gives us additional reason to include insects in animal advocacy.
Qualifications and counter-considerations
To be clear, the considerations reviewed above merely push toward increasing the emphasis that we place on small beings such as insects — they are not necessarily decisive reasons to give primary focus to those beings. In particular, these arguments do not make a case for focusing on helping insects over, say, new kinds of beings who might be created in the future in even larger numbers.
It is also worth noting that there may be countervailing reasons not to emphasize insects more. One is that it could risk turning people away from the plight of non-human animals and the horror of suffering, which many people might find difficult to relate to if insect suffering constitutes the main focus at a practical level. This may be a reason to favor a greater focus on the suffering of larger and (for most people) more relatable animals.
I think the considerations on both sides need to be taken into account, including considerations about future beings who may become even more numerous and more neglected than insects. The upshot, to my mind, is that while focusing primarily on helping insects is probably not the best way to reduce suffering (for most of us), it still seems likely that 1) promoting greater concern for insects, as well as 2) promoting concrete policies that help insects, both constitute a significant part of the optimal portfolio of aims to push for.
My own view on strategy in brief
While questions about which beings seem most worth helping (on the margin) can be highly relevant for many of our decisions, there are also many strategic decisions that do not depend critically on how we answer these questions.
Indeed, my own view on strategies for reducing animal suffering is that we generally do best by pursuing robust and broad strategies that help many beings simultaneously, without focusing too narrowly on any single group of beings. (Though as hinted above, I think there are many situations where it makes sense to focus on interventions that help specific groups of beings.)
This is one of the reasons why I tend to favor an antispeciesist approach to animal advocacy, with a particular emphasis on the importance of suffering. Such an approach is still compatible with highlighting the scale and neglectedness of the suffering of chickens, fish, and insects, as well as the scale and neglectedness of wild-animal suffering. That is, a general approach thoroughly “scope-informed” about the realities on the ground.
And such a comprehensive approach seems further supported when we consider risks of astronomical suffering (despite the potential drawbacks alluded to earlier). In particular, when trying to help other animals today, it is worth asking how our efforts might be able to help future beings as well, since failing to do so could be a lost opportunity to spare large numbers of beings from suffering. (For elaboration, see “How the animal movement could do even more good” and Vinding, 2022, sec. 10.8-10.9.)
Final clarification: Numbers-based arguments need not assume that large amounts of mild suffering can be worse than extreme suffering
An objection against numbers-based arguments for focusing more on insects is that small pains, or a high probability of small pains, cannot be aggregated to be worse than extreme suffering.
I agree with the view that small pains do not add up to be worse than extreme suffering, yet I think it is mistaken to think that this view undermines any numbers-based argument for emphasizing insects more in animal advocacy. The reason, in short, is that we should also assign some non-negligible probability to the possibility that insects experience extreme suffering (e.g. in light of the evidence for pain in insects cited above). And this probability, combined with the very large number of insects, implies that there are many instances of extreme suffering occurring among insects in expectation. After all, the vast number of insects should lead us to believe that there are many beings who have experiences at the (expected) tail-end of the very worst experiences that insects can have.
As a concluding thought experiment that may challenge comfortable notions regarding the impossibility of intense pain among insects, consider that you were given the choice between A) living as a chicken inside a tiny battery cage for a full day, or B) being continually born and reborn as an insect who has the experience of being burned or crushed alive, for a total of a million days (for concreteness, you may imagine that you will be reborn as a butterfly like the one pictured at the top of this post).
If we were really given this choice, I doubt that we would consider it an easy choice in favor of B. I doubt that we would dismiss the seriousness of the worst insect suffering.
For their helpful comments, I am grateful to Tobias Baumann, Simon Knutsson, and Winston Oswald-Drummond.