Altruism (Part 2)

Altruism is keeping our Society together.

“Every man must decide whether he will walk in the light of creative altruism or in the darkness of destructive selfishness”- Martin Luther King, Jr.

We have already discussed the introduction about Altruism and now we  will look at it in more detail.

In altruism, the organisms benefit the other being at the cost of their own life but this is opposite to natural selection.  Natural selection states that only the survival of the fittest will survive and those who could not adapt to the environment will eventually get eliminated. Hence, Natural selection explains competition for survival whereas the altruism explains the social behavior among the community. Thus, Natural selection works for individual and Altruism works at group level.  

To check how much natural selection favors altruism we use Hamilton’s rule. Hamilton’s rule is the quantitative measure to predict that when will the natural selection favors altruism. For this we have a formula: –


c = Cost (suffered by the donor while undertaking the altruistic behaviour)        

               b = benefits (gained by the recipient of the altruism)

                r = coefficient of relatedness (is the genetic relatedness of the altruist to the beneficiary).   

The rb should be more than c because if an altruist is suffering, the cost will be more meaningful if a no. of people gets help rather than only one. The benefit should always be more than the cost. Only then Natural selection will favour altruism.

Coefficient of relatedness depends on genealogical relationship between donor and recipient. The relatives are genetically similar because they share common genes. In such case when altruistic donor who is carrying altruistic gene, share his/her food, there is certain possibility that the recipient is also carrying the copies of the same gene. More they are genetically related higher is the ‘rb’ favouring altruism. The non-relatives do not share genes and hence their ‘rb’ will be less, favouring very less or no altruism. The costs and benefits are measured in terms of reproductive fitness. Reproductive fitness reflects the ability of individuals to pass on their genes to subsequent generations.

Such altruistic gene reduces the fitness of the donor but boosts the fitness of its relatives, who are also carrying the same gene. Such behaviour among the community increases the copies of altruistic genes, which are further transferred to next generation. And thus, promoting altruistic behaviour. Hence, Hamilton rule explains that the gene of altruism can spread by natural selection.

For example, a female Monkey with a well-nourished offspring nurses a starving offspring of a full brother because the benefit to his brother compensates more for the loss to himself since the survival probability of her non-starving offspring is only slightly reduced. This can be understood by considering the relatedness coefficient. Given that, the average genetic relatedness (that is, r) between two full brothers is 0.5, then according to Hamilton’s rule (0.5 × 1) > 0.25.

Let’s see the relatedness coefficient: –

Relationship to youRelatedness coefficient
Parent, child                                   ½
Grandparent, grandchild                                   ¼
Great-grand parent, Great grandchild                                   1/8
Nth level ancestor                                   1/2n

Hamilton’s rule comes under the theory of inclusive fitness (in which an organism’s genetic success is believed to be obtained from collaboration and altruistic behaviour). Inclusive fitness is of two types Direct fitness and indirect fitness.

                          Inclusive fitness = Direct fitness + Indirect fitness

Direct fitness is the number of offspring produced directly by an individual, and indirect fitness is the number of related individuals produced, multiplied by the degree of relatedness of those individuals.

Inclusive fitness suggests that altruism happens among organisms who share a given percentage of genes enables those genes to be passed on to succeeding generations.

Inclusive fitness which applies only to relatives is known as kin selection.

Kin selection, by this theory we can understand that when in a situation an altruist has three options a relative, her kids, and someone stranger then an altruist will prefer to help his kid or the relative only.

A popular example of kin selection is: –

Alarm calls – in closely related groups such as squirrels and apes put themselves at risk to warn relatives of approaching predators.

Different emotions lead to altruism like empathy and elevation. Empathy for others seems to encourage altruism. Another emotion called elevation appears to inspire altruistic behavior too.

The evolutionary biologist JBS Haldane once remarked “I would gladly lay down my life for two brothers or eight first cousins”.it captures the idea of Hamilton’s rule quite nicely. Haldane understood that each person shares on average 50% of his or her alleles with each and decides how they himself should be willing to lay down his life to save those two brothers.

Altruism is not just something we should only think about but should cultivate it in ourselves and spread kindness, of course keeping ourselves in a safe position.

Altruism Quiz –

Check your score and find out how Altruistic you are…

References –

Shikhajyoti Baruah
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I am a Postgraduate Biotechnology Student seeking to better understand how biological activity motivates and shapes human lifestyle and their surroundings. I choosed Biotechnology because we get a wider field of knowledge and it opens us up to think differently.
I like storytelling, dancing and writing and also i love playing guitar.
I was selected in youth parliament which was held in the year of 2015.
And have also participated in Model United Nations, in one of the MUNs i was awarded with verbal mention.

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