Imagine a unique set of scales that measures the value of life. If a single human were on one side, how many chimpanzees (our closest genetic relatives) would need to be on the other side before the scales tipped in their direction?

This may seem like an abstract, irrelevant or even offensive question to some people. But it was made horrifically real by the death last week of Harambe, the Cincinnati Zoo gorilla who was shot after a young boy fell into his enclosure.

Zoo handlers were faced with the agonising decision to take Harambe’s life to ensure the young boy would not lose his. The response to this event online has varied from anger, to sadness, through to considerations of how much choice the zoo’s staff really had. How do we decide what our own lives are worth compared with other species?

People are upset over the death of Harambe. YouTube

Perhaps we can try to frame the comparison in relative terms. There are 7.4 billion human beings on the planet, whereas Western lowland gorillas are critically endangered. Does a human life hold more value than that of a member of a critically endangered animal species?

Harambe’s death suggests that the instinctive answer is yes, but is there a point at which some people’s moral scales might tip the other way? Our research suggests there might be.

The Concept Of ‘Moral Expansion’

No one expects an easy answer to this question. But the fact that we can even ask it shows that our moral sensibilities have expanded beyond the boundaries of our own species.

Many of us feel a deep moral responsibility not just to protect our fellow humans, but to guard the moral rights of entities the world over. This change, which has spanned the past few centuries, has resulted in some serious ethical challenges to the ways we interact with other species and the environment.

Recently, animal rights organisations in the United States have fought for the legal personhood status of chimpanzees like Tommy, while animal advocates have petitioned the United Nations for a Declaration of the Rights of Great Apes since 1993.

In the meantime, a river in New Zealand has been officially granted legal personhood status (similar to the status given to corporations), making the river a legal “person” with its own rights and interests under law.

In line with the concept of compassionate conservation, these examples highlight the narrowing of the gulf between the moral rights of humans, non-humans and the environment.

For supporters of these causes, human rights and corresponding moral standing should no longer be restricted to humans.