One of the more interesting dilemmas that animal rights critiques poses is exactly what role human beings should play as part of the animal kingdom, specifically when it comes to things like predation. After all, if we suppose that birds have rights, not only does the turkey on a farm have a right not to become my Thanksgiving meal, then so does the bird chirping outside my window have a right not to become the victim of the neighborhood serial killer of the feline persuasion.

Occasionally a variety of this argument is used as an attempted reductio ad absurdum against the case for animal rights — that if one were to take seriously the claims made by animal rights theorists that humans should be out there attempting to prevent lions from preying on zebras and antelope. Taking that to a further extreme, perhaps instead of attempting to preserve endangered carnivore species, human beings should instead allow them to go extinct since this would reduce the total suffering in the world on this view.

Some people, especially in the transhumanist community, take this idea very seriously, however. In September, The New York Times published an op-ed by Rutgers University philosophy professor Jeff McMahan on this very topic. Once you get past the tedious introduction referencing Isaiah and whether or not we would be “playing God” by making wholesale changes in carnivorous species, McMahan gets to the heart of the matter,

There is an element of truth in this view, which is that our moral reason to prevent harm for which we would not be responsible is weaker than our reason not to cause harm.  Our primary duty with respect to animals is therefore to stop tormenting and killing them as a means of satisfying our desire to taste certain flavors or to decorate our bodies in certain ways.  But if suffering is bad for animals when we cause it, it is also bad for them when other animals cause it.  That suffering is bad for those who experience it is not a human prejudice; nor is an effort to prevent wild animals from suffering a moralistic attempt to police the behavior of other animals.  Even if we are not morally required to prevent suffering among animals in the wild for which we are not responsible, we do have a moral reason to prevent it, just as we have a general moral reason to prevent suffering among human beings that is independent both of the cause of the suffering and of our relation to the victims.  The main constraint on the permissibility of acting on our reason to prevent suffering is that our action should not cause bad effects that would be worse than those we could prevent.

That is the central issue raised by whether we ought to try to eliminate carnivorism.  Because the elimination of carnivorism would require the extinction of carnivorous species, or at least their radical genetic alteration, which might be equivalent or tantamount to extinction, it might well be that the losses in value would outweigh any putative gains.  Not only are most or all animal species of some instrumental value, but it is also arguable that all species have intrinsic value.  As Ronald Dworkin has observed, “we tend to treat distinct animal species (though not individual animals) as sacred.  We think it very important, and worth a considerable economic expense, to protect endangered species from destruction.”  When Dworkin says that animal species are sacred, he means that their existence is good in a way that need not be good for anyone; nor is it good in the sense that it would be better if there were more species, so that we would have reason to create new ones if we could.  “Few people,” he notes, “believe the world would be worse if there had always been fewer species of birds, and few would think it important to engineer new bird species if that were possible.  What we believe important is not that there be any particular number of species but that a species that now exists not be extinguished by us.”

. . .

Yet the extinction of an animal species is not necessarily bad for its individual members.  (To indulge in science fiction, suppose that a chemical might be introduced into their food supply that would induce sterility but also extend their longevity.)  And the extinction of a carnivorous species could be instrumentally good for all those animals that would otherwise have been its prey.  That simple fact is precisely what prompts the question whether it would be good if carnivorous species were to become extinct.

. . .

Here, then, is where matters stand thus far.  It would be good to prevent the vast suffering and countless violent deaths caused by predation.  There is therefore one reason to think that it would be instrumentally good if  predatory animal species were to become extinct and be replaced by new herbivorous species, provided that this could occur without ecological upheaval involving more harm than would be prevented by the end of predation.  The claim that existing animal species are sacred or irreplaceable is subverted by the moral irrelevance of the criteria for individuating animal species.  I am therefore inclined to embrace the heretical conclusion that we have reason to desire the extinction of all carnivorous species, and I await the usual fate of heretics when this article is opened to comment.

Transhumanists who go down this road typically posit altering the DNA of carnivores and omnivores so that they no longer need/desire the flesh of other animals (which McMahan does mention), or producing meat  in a non-cruel way (for example, growing it in a vat and then distributing it somehow).

An alternative that McMahan seems to ignore might be modifying prey species so that they no longer suffer when they are killed by predators which would allow predation to continue without reducing the number of species or radically changing the ecosystem in other ways.

It is also curious that McMahan and others tend to stop there. After all, predation is not the only cause of suffering in the animal kingdom. For example, in 2009 a 39-year-old chimpanzee kept in captivity at a zoo in Oregon died from what is believed to have been either a heart attack or stroke. Presumably, either way the chimpanzee’s death involved quite a bit of suffering.

Would human beings also be obliged to then re-engineer animals to prevent the sort of suffering that occurs even from “natural” deaths? If we are somehow obliged to prevent suffering due to predation, it becomes difficult to argue that we can still tolerate other forms of suffering that animals experience.