Explain this Darwin: finding altruism in unusual suspects
By Desiree Chevailer
Lance Writer
February 4, 2009
 Bob: “Hey! Did you hear the one about the naked mole-rat?”
Jane: “Um… The naked mole rat? That pretty much sounds like a joke in itself.”
Bob: “No seriously! This one’s great! Two naked mole-rats walk into a bar. The one spots a sexy lady naked mole-rat and says, ‘Hey, I’d die tomorrow without any complaints if I could make some babies with her!’ The other naked mole rat takes a drink and says ‘Nah, she ain’t all that. But I’d give my life for two brothers or eight first cousins!’ [elbow jab] Isn’t that brilliant! Do you get it? Huh? Huh?”
Jane: “I’m very confused. And the phrase ‘sexy lady naked mole-rat’ makes me feel very uncomfortable.”
Dear reader: Never fear, this is not some sort of pre-Valentine’s day piece on dates from hell. Believe it or not, there are actually organisms that would die and/or give up their sex life in order to save the lives of others! And not just naked mole rats, either!
Across the animal kingdom, altruistic behaviours, which are acts that benefit a recipient with no apparent advantage to the actor, persist in the face of an evolutionary process that is driven by natural selection, or simply ‘survival of the fittest.’
Fitness in this sense is defined not only by the ability to survive in a particular environment; an individual’s genes must also be passed on to future generations.
The friction between altruism and natural selection is then easily observed; if fitness requires survival and passing on your genes, why would you risk your life or reproduction for others? Why hasn’t natural selection removed altruistic behaviours?
What do naked mole-rats have to do with this?
Many scientists have found evidence that the answer to this question is relatedness- as implied by the terribly awkward joke above.
Given a situation where an individual is more likely to pass on their genes through an act other than reproduction, they will likely do so.
For example, if by sounding an alarm call an individual might risk death by inviting attention from predators to themselves, they may pursue the action anyway if by sounding the alarm call the actor has the opportunity to save a certain number of relatives.
By acting altruistically, the individual has increased their fitness indirectly by contributing to the survival and reproduction of their relatives. Therefore, altruistic acts can still make sense within the framework of evolution when those acts increase an individual’s fitness.
William Hamilton first proposed relatedness as the solution to the altruistic behaviour puzzle in the early sixties with the theory of kin selection.
Hamilton found that fitness could be accrued directly, via reproduction, but also indirectly, through the survival and reproduction of relatives.
Hamilton actually worked out an equation to figure out the likelihood that an individual will commit an altruistic act, which is where the “I’d give my life for two brothers and eight first cousins” joke originally told by the late J.B.S Haldane (a well-known geneticist and evolutionary biologist) came from.
The equation takes into account the relatedness between two individuals, the benefits associated with an action that would increase another individual’s direct fitness and the costs to the actor.
In nature, evidence supporting the theory of kin selection is abundant. Eusocial societies (examples include ants and some species of bees, wasps and rodents) are characterized by a high level or organization, division of labour, overlapping generations and cooperative care.
How does it all make sense in the greater evolutionary framework? Let’s use a typical ant colony as an example. In an ant colony, individuals are 75 per cent related to their sisters because unlike species where males and females are both diploid (have two sets of chromosomes) male ants are haploid.
Females are still diploid, so when a male and female mate, males only have one specific set of chromosomes to contribute.
Therefore, female offspring, who will be diploid, receive one of two sets from their mother, and one definitive set from their father, making them more related to their sisters than to any would-be offspring (offspring would be 50 per cent related to their mother and father).
The pursuit of increased indirect fitness in turn motivates workers to aid in the survival and reproduction of their queen. Another example can be observed in the naked mole rat, who displays behavioural differences based on relatedness (less-related individuals shove each other more than related individuals).
In other cases, like the alarm-calling described earlier, which is common in prairie dogs, this behaviour is generally considered to be the result of many closely related individuals being born in and residing in the same general area.
While scientists have already presented a variety of studies supporting the theory of kin selection, further research is still needed to better understand altruistic genes.
Eusociality, in particular, is a complex problem for evolutionary biologists as they continue to study real-life examples among different species and habitats.
For more on evolution and natural selection, check out Adaptation and Natural Selection by George C. Williams or the best-selling The Selfish Gene by Richard Dawkins.
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