Kid: “I don’t look anything like my mom!” — Crossbreed Adoption: A Challenge to Darwinian Theory

Maternal Instinct Cross the Species Line

Cross species adoption is a phenomenon that has been puzzling scientists for years. Such behaviour contradicts Darwinian Theory of Natural Selection and Evolution, which is the selection of behavioural traits that increases the rate of survival and reproduction. Adopting someone else’s young that holds no similar traits and investing precious resources and energy in ensuring their survival not only reduces the mother’s reproductive success, but also the species’ own rate of survival. The Darwinian Theory fails to explain this phenomenon, that happens (as seen in video) not only between cats and dogs, but across all types of species, such as a baby chimpanzee being nursed by a leopard who preyed on its mother, and a young deer nursed by a feline cat.

Dog adopts a litter of kittens

The title of the video is called “Maternal Instincts crosses the Species Line”. But instincts is categorized under learning, which is also under natural selection, again, the Darwinian Theory. So we then start to question, if natural selection ultimately aims to bolster the rate of survival and reproduction, and if cross breed adoption is proven to challenge that idea, then can we truly say that cross breed adoption is a result of strong maternal instincts?

It could be possible. In the National Wildlife Magazine’s “Parenting Paradox”, written by Sharon Levy, it mentioned that such a behaviour may be advantageous in terms of gaining parenting experience. Moreover, the research article “Cross-Genus Adoption by Wild Capuchins” mentioned Maestripieri’s (2001) suggestion that the “adoption of an unrelated infant is an evolutionary maladaptive consequence of mechanisms selected to promote mother-infant bonding”. This article can be found at:,%20692%20-%20700%202006.pdf.

But then again, these are all human interpretations of what we observe. Whether they truly represent the meanings of such behaviour, we can never be sure.


Cross-Genus Adoption of a Marmoset (Callithrix jacchus)
by Wild Capuchin Monkeys (Cebus libidinosus):
Case Report Patricia Izar, Michele P. Verderane, Elisabetta Visalberghi, Eduargo B. Ottoni, Marino Gomes De Oliveira, Jeanne Shirley and Dorothy Fragaszy.

Patricia Izar,  Michele P. Verderane,Elisabetta Visalberghi, Eduardo B. Ottoni, Marino Gomes De Oliveira, Jeanne Shirley & Dorothy Fragaszy, 2006. Cross-Genus Adoption of a Marmoset (Callithrix jacchus) by Wild Capuchin Monkeys (Cebus libidinosus): Case Report. American Journal of Primatology, 68:692–700.

“Parenting Behaviour,” by Sharon Levy. National Wildlife Magazine, Aug/Sept 2002. URL: (assessed on 5 April 2010).

“Maternal Instinct Crosses the Species Line,” by CBS News Youtube Channel, 22 April 2009. URL: (assessed on 6 April 2010).

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