Quantifying Animal Farmed Animal Suffering with Neuron Counts

The question of what weight to give to human interests and to nonhuman animal interests is difficult.67 Humans are literally outweighed by farmed animals: land-based farmed animals have 70 percent more biomass than all humans.68 Land-based farmed animals also outnumber humans greatly, by a factor of three to one, with 25 billion chickens, 1.5 billion cattle, 1 billion sheep, and 1 billion pigs alive at any one time; farmed fish outnumber us, at a very rough estimate, ten to one, with around 100 billion farmed fish alive at any one time. However, these species do not all have equal capacity for wellbeing, and it’s hard to believe that capacity for wellbeing does not matter at all when comparing the interests of different species. Accounting for differences in capacity for wellbeing does not entail that other species have lower moral status than humans. Rather, it gives their wellbeing equal weight but recognises that some species simply have less of it than others.

To capture the importance of differences in capacity for wellbeing, we could, as a very rough heuristic, weight animals’ interests by the number of neurons they have. The motivating thought behind weighting by neurons is that, since we know that conscious experience of pain is the result of activity in certain neurons in the brain, then it should not matter more that the neurons are divided up among four hundred chickens rather than present in one human. If we do this, then a beetle with 50,000 neurons would have very little capacity for wellbeing; honeybees, with 960,000 neurons, would count a little more; chickens, with 200 million neurons, count a lot more; and humans, with over 80 billion neurons, count the most.69 This gives a very different picture than looking solely at numbers of animals: by neuron count, humans outweigh all farmed animals (including farmed fish) by a factor of thirty to one. This was very surprising to me; before looking into this, I hadn’t appreciated just how great the difference in brain size is between human beings and nonhuman animals.

If, however, we allow neuron count as a rough proxy, we get the conclusion that the total weighted interests of farm land animals are fairly small compared to that of humans, though their wellbeing is decisively negative.