By: Jenny Lam
An organism’s behavior is said to be altruistic if it benefits the survival and reproductive success of other organisms at the expense of itself (Okasha). In other words, altruistic behaviors involve sacrificing oneself to help others. From a Darwinian perspective, biological altruism appears counterintuitive, as it would be expected for organisms to act in ways that increase their own chances of survival and reproduction, rather than purposefully lowering them to help out another organism. It is natural to wonder how these behaviors arise through natural selection and how they have prevailed through evolution, despite bringing harm to the altruistic individual.
To describe the reproductive success of an organism, the term ‘fitness’ is used, which is the contribution that an individual makes to the gene pool of the next generation relative to the contributions of other individuals in the population (el-Showk). Although fitness is commonly viewed as a measure of strength or health, from an evolutionary point of view, it is known as a measure of reproductive success and survival. Biological altruism is defined as behavior that reduces an individual’s personal fitness but increases the overall fitness of other individuals within the population (Taylor). These altruistic behaviors can be seen in numerous animals, especially those with complex social structures. For instance, a Belding’s ground squirrel that sees its predators gives a high-pitched alarm to warn other individuals in the area of danger, allowing them to retreat to their burrows and avoid predators (Sherman). However, this alarm puts the altruistic squirrel at risk since it draws attention to its location. Additionally, female vampire bats donate blood to each other and share regurgitated blood to other bats who weren’t able to obtain a meal that day. Vampire bats display reciprocal altruism, a behavior in which an individual will temporarily reduce its fitness to increase another unrelated individual’s fitness, with the expectation that it will receive the same treatment at another time (Greshko).
Group Selection Theory:
An early theory to explain altruism’s role in natural selection was group selection, proposed by Charles Darwin in The Descent of Man (1871). He argued that although self-sacrificial behaviors harm the individual carrying it out, these behaviors could be beneficial at the group level; groups that were more willing to sacrifice themselves for the common good were more likely to survive compared to their more selfish counterparts. Later, several authors proved group selection to be a weak and limited evolutionary force through mathematical models, which showed that its effects were significant only in specific conditions. A problem with group level-altruism is that it can easily be exploited from within by selfish individuals who freeload by receiving the benefits of the others’ altruistic behavior, but not acting altruistically in return (Okasha). These selfish individuals are more likely to reproduce due to receiving the benefits of altruism without being altruistic, leading to an increase in the frequency of the “selfish” gene in new generations, rather than the “altruistic” gene.
Kin Selection and Hamilton’s Rule:
A more popular explanation arose in the 1960s to explain how altruistic behavior could have prevailed without group selection: kin selection, also known as the inclusive fitness theory (Okasha). Proposed by William Hamilton, kin selection is a type of natural selection that favors the reproductive success of an individual’s relative, even at the expense of the individual’s itself (Queller and Strassmann). If an altruistic gene causes an organism to behave altruistically towards its kin, this increases the family member’s chances of survival and reproduction. As a result, the family member is more likely to pass down the gene in question, since related organisms have a larger chance of bearing the same genes than unrelated organisms. In other words, altruistic genes can spread by causing its bearer to reduce its own fitness in order to increase the fitness of its relatives. Relatives are more likely to carry the same gene because they are related, resulting in them passing on that altruistic gene to future generations. An animal can maximize its genetic representation in the following generation by helping its close relatives. The inclusive fitness of an organism is measured by the survival and reproductive success of its kin, so although altruistic behaviors may decrease an organism’s individual fitness, it can increase the inclusive fitness of the individuals in the population (Gardner and West).
Hamilton demonstrated that natural selection will favor an altruistic gene when a condition known as Hamilton’s Rule is satisfied. 3 variables in an act of altruism are considered: the benefit to the recipient, B, which is the average number of extra offspring produced due to the altruistic act, the cost of the act, C, which is how many fewer offspring that altruistic animal produces, and the coefficient of relatedness, r, which is the fraction of genes shared by the two organisms (e.g. siblings share ½ of their genes on average). When the benefit B, multiplied by the coefficient of relatedness r exceeds the cost of the altruistic act C (i.e. rB>C), Hamilton’s rule is satisfied, indicating that altruism will be favored by natural selection in that case (Okasha). This suggests that the degree of altruism is higher in close relatives compared to distant relatives, as closer relatives would have a higher value of r since they are more likely to have genes in common.
The Gene’s-Eye View of Evolution:
Altruistic behavior brings up another famous yet controversial theory popularized by Richard Dawkins: the gene’s-eye view of evolution, or the selfish gene theory. Dawkins proposed that many genes in an organism’s genome may be in conflict with one another and that these genes act to increase their presence in the next generation, even at the organism’s expense (Madgwick). This theory contrasts with Darwin’s original organism-centered view of natural selection by suggesting that the gene is the central unit of natural selection and evolution. The idea that genes in an organism can be in conflict with one another can be puzzling at first, as genomes are usually viewed as a singular unit whose DNA work together to enhance an organism’s fitness. Called intragenomic conflict, the phenomenon arises when a gene promotes its own replication in a way that is harmful to other genes of the same genome, even if it has a negative effect or no effect on the organism (Werren). These genes are known as selfish genetic elements and they can be used to explain altruistic behaviors such as kin selection and the green-beard effect (Ågren and Clark). First proposed as a thought experiment but later found in animals such as red fire ants, the green-beard gene is one that causes a unique phenotypic effect (e.g. a green beard) that allows the organism to recognize it in others and act altruistically towards those individuals, increasing their fitness. This results in a higher chance of increased propagation of that green-beard gene in future generations. Although the organism is altruistic, the gene can be considered selfish, benefitting itself at the expense of the altruistic individual.
The basis of biological altruism remains both interesting and controversial with much still left to be explored in the future. Unlike psychological altruism, which involves helping others without expecting anything in return, biological altruism is defined by behavior that increases the receiver’s fitness at the expense of that of the giver. Numerous theories have been developed through the years that attempt to explain this phenomenon, two popular examples being kin selection and the selfish gene theory, which both relate maximizing genetic representation in the population gene pool to altruistic behaviors. These concepts are currently being used to examine human behavior from an evolutionary perspective, and research connecting kin selection in humans and emotional closeness can provide more understanding of altruistic tendencies (Colquhoun et al.). By incorporating concepts of biology and evolution to gain a better understanding of altruism in humans, one can apply this knowledge to encourage behavior that benefits other people and society as a whole.
Questions
Is biological altruism the same as ‘real altruism’?
Many people are familiar with altruism, meaning “acting to help someone else at some cost to oneself, with special emphasis on the selfless intentions of the actor” (“Altruism”). Some argue that biological altruism is not “real” altruism, as concepts such as kin selection and the green-beard effect are centered around selfish genes trying to maximize representation in the gene pool at the expense of the altruistic organism. The problem with comparing biological altruism to this definition of altruism is that one cannot be equated with the other, as the two are inherently different, with biological altruism being based on fitness, rather than the conscious self-interests of the individual (Okasha). It can also be argued that most living things do not act consciously, and as a result, cannot have selfish or selfless intentions behind their actions.
What does it mean when a gene is “selfish”?
A ‘selfish’ gene is one that can enhance its own inheritance at the expense of other genes in the same genome, but are either neutral or harmful to the individual carrying the gene. The phrasing of “selfish genes trying to maximize representation” is not entirely accurate, since genes are not creatures with conscious goals and interests, but rather, it is a metaphor to explain altruism through a Darwinian natural selection process and to show that the effect of these genes can be described as if they were selfish. Dawkins himself admitted that his use of the word “selfish gene” is misleading since it implied that genes are sentient beings by giving them an anthropomorphic quality (Ridley). He mentioned that “immortal gene” would have been a more accurate name for his ideas, as “genes are in a sense immortal. They pass through the generations, reshuffling themselves each time... Natural selection will favour those genes which build themselves a body which is most likely to succeed in handing down safely to the next generation a large number of replicas of those genes.”
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