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Researchers Ponder Why Animals Adopt Other Species’ Orphans

Beliefs about what animals “should do” are often hampered by a lack of common sense reasoning and an outdated evolution theory

At The Conversation, evolutionary anthropologist Isabelle Catherine Winder (pictured) and anatomist Vivien Shaw pose a question, “Animal adoptions make no evolutionary sense, so why do they happen?

For instance, scientists working with gorillas in Rwanda recently found the gorillas band together to take care of orphans. In these cases, young peers and (surprisingly) dominant adult males can be key to immature orphans’ survival. Perhaps it really does take a village to raise a child.

Meanwhile researchers in DR Congo found that bonobos (apes closely related to chimpanzees) go even further, and sometimes adopt babies from a different social group. We even have examples of cross-species adoption, such as the dolphin who adopted and nursed a melon-headed whale, and a group of capuchin monkeys who raised a marmoset.

Isabelle Catherine Winder, Vivien Shaw, “Animal adoptions make no evolutionary sense, so why do they happen?” at The Conversation

One could, of course, add many other examples. But there is something a little “off” in the way Winder and Shaw frame the evidence. For example, we are told that “Scientists used to think that humans are special because we have larger brains than other animals” but now “some experts in human evolution” believe that we evolved to be kinder than other animals are.

Wait. Animals don’t have reason or moral accountability but there is abundant evidence that mammals and birds have feelings. And feelings often follow their own rules. A cat may adopt a duckling, under the right circumstances or a lioness may adopt an oryx (the video skips immediately to the lioness and the oryx):

Winder and Shaw point out that traditional evolution theory doesn’t really account for these feelings:

Adoptions like these puzzle biologists. From an evolutionary perspective, what matters is how many copies of your genes make it into the next generation. Adopting a niece or nephew might therefore make sense. A biological sibling shares on average 50% of your genetic material, and their offspring inherits about half of that (25%).

If the cost of raising your niece is less than the cost of having another baby, you may ensure more copies of your genes survive by helping your niece. The idea that an animal might be altruistic (helpful) to members of their family to increase their own evolutionary success is called kin selection.

Adopting an unrelated child, however, can’t be explained by kin selection. It’s a choice that incurs significant cost, but does not result in more copies of the adoptive parent’s genes being passed on.

Isabelle Catherine Winder, Vivien Shaw, “Animal adoptions make no evolutionary sense, so why do they happen?” at The Conversation

Of course, few adoptive human parents approach the matter that way and animals are surely governed by more immediate sensations. So what would cause animals to put territorial or predatory instincts aside?

Winder and Shaw suggest several factors, including

● Domestic animals, fed and protected by humans, are free to indulge mothering or protective instincts. They may not even take note of differences between species.

● Among wild animals, the urge to nurture may overcome other urges (yes, that is a gosling in the video but the cranes don’t care) And why should they care? That’s officially called “misplaced reproductive function.” But, uncommon as it is, it contributes a little bit to the maintenance of the biosphere and may have other functions we don’t yet know.

● In large herds, adoption of an orphan may give young females practice with nurturing. It’s relevant, perhaps, that the young are usually only with an adoptive parent for one season anyway.

Mulling various theories to account for the evidence, Winder and Shaw conclude,

Attempts have been made to look for “hidden” relationships between helper and recipient, to make altruism “fit” with evolutionary selfishness. Perhaps instead we may just have to accept that humans are not unique in their capacity to care for and help each other.

Isabelle Catherine Winder, Vivien Shaw, “Animal adoptions make no evolutionary sense, so why do they happen?” at The Conversation

Well yes. If we don’t feel a need to affirm kin selection theory or selfish gene theory, maybe we don’t need an explanation — “evolutionary” or otherwise — for animals adopting unrelated animals. Animals think with their feelings, which do not always follow the theory. If whatever they are doing doesn’t kill them or their kind, that’s enough.

But when Winder and Shaw write, “we may just have to accept that humans are not unique in their capacity to care for and help each other,” again, wait.

What makes humans different is that many humans went out and spent decades studying animals and reporting back to the rest of us. So now you are reading about their work. The animals are simply doing what they do and not reporting or reading about it. That is the unbridgeable gap. Any theory that states or implies otherwise is in stark conflict with everyday evidence.

You may also wish to read:

Bonobo chimpanzees adopt orphans, a first for great apes. But this story is not what it seems. Let’s cut through some pop science assumptions. In a way, the willingness of our domestic animals to adopt other animals’ offspring — relative to that of the bonobos, according to researchers — is an argument for human exceptionalism. Given a chance, we break nature’s rules. We do things differently.

Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul; and with neurosurgeon Michael Egnor of the forthcoming The Human Soul: What Neuroscience Shows Us about the Brain, the Mind, and the Difference Between the Two (Worthy, 2025). She received her degree in honors English language and literature.

Researchers Ponder Why Animals Adopt Other Species’ Orphans