Darwin, in his theory of natural selection, suggested that a disproportionate amount of resources – food, for example - leads to competition for obtaining those resources. This, in turn, leads to a struggle for existence. The ones who have the ability to adapt to their environment are the ones that succeed in using those resources. These organisms are the ones that end up reproducing thus giving rise to another generation of organisms that also have the ability to survive in the specific environment. Those organisms which cannot successfully utilise the resources presented cannot survive long enough to reproduce and end up not producing any offspring. Eventually, this population consists of better-adapted individuals predominating with only a very small fraction of ill-adapted individuals. This picture can be better explained with the help of an example. Many species of plants have evolved to produce certain toxins to prevent them from being eaten by herbivores. Here, our organism is the plant, the environment is the animal that eats the plant, and adaptation in response to the environment is the production of toxins. This is, of course, an oversimplification of the plant-herbivore evolutionary relationship but it gets the point across nicely. One must adapt to the environment or get eaten!

Social Behaviour:

While some living beings were locked in an inter-individual conflict for survival. Certain kinds of animals evolved mechanisms such as cooperation and altruism in response to the selection pressure acted on them. Collectively, this may be called as social behaviour or eusociality since it suggests a higher order of organization than solitary animals. ‘Social’ behaviour does not have a single origin; instead, it has arisen separately in different animal groups at various points on an evolutionary timescale. Such animals live in groups often called colonies or societies. Amongst its characteristics, perhaps the most remarkable one is that of division of labour and brood care. In this context, ‘division of labour’ refers to the reproductive and non-reproductive division of labour. Only one or a few individuals are capable of reproducing, others are engaged in activities such as brood care. Brood care means the young of the colony are reared by various other individuals to ensure their survival. Biologists have been fascinated by such an intelligent system established to ensure continued survival of the species.

Insect Societies:

Insect societies are excellent systems to study social behaviour since each colony shows a profound division of labour among its members. Each individual is specialised to do one type of work. In many cases, such differentiation of work also reflects on their morphology. The guards are often larger in size than those who are engaged in nursing the young, for example. Ordinarily, a hive consists of queens, workers, and drones. Each one of them has defined functions. The Queen is the only one who is capable of laying fertilised eggs. She mates with the drones early on in her life. The drones are the male bees present in the colony. With a population of a few hundred, drones mate with the queen and die soon after. The workers are present in the colony in the most numbers. They perform all the tasks essential for the survival of the colony ranging from foraging to taking care of the young to defending the colony. In some cases, workers do lay eggs but in general egg-laying by workers is discouraged by various mechanisms including killing worker-laid eggs as well as more aggressive treatment of the laying workers. A possible explanation for this is that if all workers abandon their assigned tasks in favour of reproduction, the hive would not be able to function as smoothly.

Evidence in support of this idea comes from observations of queen-less colonies in which there is a greater proportion of egg-laying workers than in colonies with a queen. Queen-less colonies are not as efficient at carrying out all the tasks that are required for colony maintenance This is because a greater proportion of workers is engaged in reproduction and egg laying which reduces the workers who are available for these tasks. Due to a significant portion of the colony producing offspring (as opposed to just the queen) the number of young ones that require care exceeds what the colony can handle which only adds to its woes. Colonies that have a queen show a clear division of labour in terms of reproduction and other essential tasks. Because the queen is the only member of the hive that can lay fertilised eggs, workers can carry out their specialised jobs easily allowing the colony to function in perfect tandem as a single self-sufficient unit. These observations are not novel in any way but evolutionary biologists struggled for years in explaining this phenomenon, including Charles Darwin! Darwin had indeed observed such unusual behaviour but could conveniently circumvent it by assuming the colony to be a single reproduction unit while ignoring the individual members of the same. It was not until the 1960s that a comprehensive explanation was obtained for such altruistic behaviour in the form of Hamilton’s rule. Hamilton's rule says that an individual is more prone to self-sacrificial behaviour if it benefits a close relative than another unrelated individual. This idea fits well in the context of insect societies . The workers which are the genetic offspring of the queen sacrifice their own reproduction (by tending to the young, searching for food, guarding the colony, etc.) to benefit the latter's ability to produce more progeny. By Hamilton's rule, the workers are more closely related to their mother (the queen bee) than their sisters (other workers). Therefore, it makes sense that workers would help enhance the reproductive ability of the queen over other workers.

As with new ideas in science, this one took some time to be accepted by the larger scientific community as well. This process, however, was sped up in the particular case owing to the mounting evidence in favour of altruism. The concepts of competition and altruism are completely opposite yet are found to be occurring in nature together. This finding only enriched the existing trove of knowledge about life on earth.  

Only those insect societies in which the males are haploid. Further complications are introduced when societies with diploid males are considered. For the sake of simplicity, the latter will remain outside of the scope of this article. 

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