Written by Dr Juliet Turner
I like to think of myself as an ant colony. Each cell is ant, and many different cells (ants) work together to form the complex higher entity that is Me (the ant colony). This might sound a bit insane, but it has a real scientific basis, and one that I explored in depth during my DPhil before I started work at the GWCT.
So why do I think of myself as an ant colony? To justify this, I need to go back to basics. All complex life depends on division of labour and cooperation between smaller parts.
In a multicellular organism such as a human being, there are two broad categories of cell. First, the somatic cells – skin cells, blood cells, etc. Second, the germline cells – sperm and eggs. Somatic cells replicate through asexual reproduction (mitosis) but ultimately die when you do. Germ cells, however, undergo sexual reproduction (meiosis). If you die, your germ cells can live on, having built themselves into a new cellular arrangement (a baby).
Ant colonies have a similar system. Worker ants are sterile, like somatic cells. Queens are vessels for propagating genes to the next generation, like our germline cells. Just as somatic cells cooperate to ensure the survival of your germline, workers cooperate to ensure the survival and reproduction of their queen. New colonies are formed when queens disperse, mate, and settle down to produce a brood. That brood eventually develops into a colony.
If you ever had an ant farm as a child, and captured worker ants but not the queen, what you had was not a true colony. It is similar to how a petri dish containing blood cells is not a human being. Queens and workers have total mutual dependence. Reproduction itself has been allocated as a specific role for only a subset of the population. Just as our bodies are colonies of cooperating and mutually dependent cell types, ant colonies can be thought of as higher-level individuals, made up of cooperating castes. The division of individuals into reproductive and non-reproductive castes is called reproductive division of labour– a key focus of my thesis.
There can also be additional division of labour among the non-reproductive individuals. Somatic cells are divided into skin cells, muscle cells, blood cells, etc. Ant workers are divided into soldiers, foragers, gardeners. This is called non-reproductive division of labour. In the very socially complex leafcutter ants of the Neotropics, there are specialised foragers that bring food into the nest, just as we bring food into our body for digestion. Others remove waste from the centre of the nest and deposit it in a designated landfill area analogous to our digestive system. A soldier caste defends against intruders much like our own immune system.
Sometimes ant workers go rogue. They neglect their obligations to the colony and instead try to just replicate themselves. In social evolution, we call this ‘cheating’ behaviour. These workers reproduce asexually, laying unfertilised eggs that develop into clones of themselves. In our cellular bodies, when cells do this we call it cancer. A cell that multiplies uncontrollably forms a tumour. Both ant colonies and human bodies have ways of dealing with these ‘cheats’ – immune cells suppress cancer, and ant workers police each other; patrolling the colony and destroying any eggs not laid by the queen.
Both ant colonies and multicellular bodies are among the most cooperative and complex systems in nature. They have evolved many analogous characteristics. An organism is a cooperating assemblage of cells. An ant colony is a cooperating assemblage of organisms (a superorganism). However, this is more than just an analogy – both represent distinct levels of biological organisation. You can think of life as layers of biological organisation, nested inside each other like Russian dolls.
Drawing the line of deciding what an ‘individual’ is becomes much harder when you view things this way. Once an additional layer of biological organisation evolves as a stable form, the ‘individual’ is the new greatest whole. Once, a long time ago in our evolutionary past, our ancestors were individual single-celled life forms. Now, our cells are just tiny components of a much larger and more complex being. Ants and some other insects have evolved a step above this, where a colony of organisms is the new higher-level individual.
Understanding the parallels between different complex systems shows us how cooperation underpins life at every level – from cells to societies.
I write more about my DPhil research in my second blog, 'My DPhil: Explaining Patterns in Complexity'.