Are Headlines Hogwash?
In this series of posts, my esteemed colleague Dr. Zen Faulkes (aka neurodojo) and I will be examining some recently published work that grabbed the headlines. We will ask the question: is the science accurately portrayed?
This week’s paper was published in Nature Communications earlier this month. It grabbed a lot of media attention with a ‘melt your heart’ photo of a mama squirrel with an adopted orphan. Headlines such as:
Squirrels Show Softer Side by Adopting Orphans
Gorrell, J., McAdam, A., Coltman, D., Humphries, M., & Boutin, S. (2010). Adopting kin enhances inclusive fitness in asocial red squirrels Nature Communications, 1 (3), 1-4 DOI: 10.1038/ncomms1022
The headlines work.
Bona fide adoption has been documented to occur in these asocial squirrel populations according to the tenets of Hamilton’s rule (rb > c). Using 19 years of data from this well-studied population, researchers calculated ‘c’ as the reduction in survival of the natal litter that would occur by adding another juvenile, and ‘b’ as the probability of that newly adopted juvenile to survive given the size of its new litter. They then calculated the degree of relatedness that would be required in order for adoption to happen. Genetic data from the population confirmed that in all observed cases, the adoptions agreed with the predictions of relatedness. In other words: the mothers’ inclusive fitness was increased when she adopted. So, perhaps it’s not the warm fuzzy feeling that is being propagated through the headlines, BUT it is adoption all the same. In addition, it is adoption that agrees with the predictions of inclusive fitness.
Let’s not forget a key part of this puzzle: regardless of the mothers’ biological fitness calculations, an abandoned orphan whose biological fitness would have otherwise been ZERO ends up with a fairly decent shot at adulthood. You can enjoy the warm fuzzies from this point of view, because there is no denying the death sentence of an infant without parental care. Thanks to the adopting squirrel mamas for saving these innocent lives.
The headline gets it wrong. Not “Flaming atomic death wrong,” just “Where’d I put that box of bandages?” wrong.
The problem is the word “altruism.” Most people take “altruism” to mean “I do something good for you.” But in biology, “altruism” means, “I do something that is good for you, even though it’s bad for me.”
That difference is important. In an evolutionary sense, doing good for someone is easy to explain if I benefit – that’s cooperation. Doing good for someone else is also easy to explain if I break even – that’s generosity. But true altruism, where I do something that’s bad for me, is fiendishly difficult to explain.
Darwin himself realized this when he considered insects like bees and ants, where sterile workers help a reproductive queen. That seems to be altruism in that tough-to-explain-way-that-evolutionary-biologist-use-the-word meaning, He wrote that the problem they posed “at first appeared to me insuperable, and actually fatal to my whole theory” (Chapter 7, On the Origin of Species).
The brilliant thing about this paper is that it shows that these mama squirrels are not being altruistic: they are being selfish. The female benefits from taking on these abandoned pups, because she only takes the adopted pup when they are related. Because the mother and the pup are related, they share a certain number of genes in common, just like the mother’s own offspring would have.
When you look at many of these cases of altruism, you see very close relationships, which means the helping individuals share a lot of genes in common. Worker bees shares 75% of their genes with their sister queen, for instance.
If the adopted pup succeeds, more of the adopting mother’s genes go forward. More importantly, it seems that the mother only adopts when she stands to gain a benefit. There’s not many cases of adoption to fit to the model, and you would expect that the adopting mother to maybe get it wrong occasionally. The behaviour is rare, but “rare” is not the same as “unimportant.”
A mother squirrel may be warm and fuzzy, but her decision to adopt is cold and calculating.
For an interview with the lead researcher, listen online at: