Superorganism as Window Into Complexity and Evolution

Should a beehive be viewed as a collection of individual organisms, or a single organism unto itself? Or both?

Over the last several days I've written about the proposition that evolution can't be described purely in neo-Darwinian terms of genetic mutation and natural selection. Some scientists say that the development of Earthly life must be seen in a framework of networked collectivity, emergent phenomena and thermodynamics.

I learned about this while researching an upcoming story on the application of complexity theory to evolutionary biology. The story started to take form last summer, when I talked with Arizona State University biologist Bert Hoelldobler about insect superorganisms -- colonies that can be defined as individuals at what is traditionally considered to be a group level.

While researching the story, I talked with evolutionary biologist Gro Amdam, a honeybee specialist and colleague of Hoelldobler. She described how the development of individual bees is determined by the interactions of an entire hive, which ought to be seen as an individual itself.

How bees went from solitary to hive-linked creatures is a mystery, but it appears to involve a phenomena known as pre-adaptation, in which gradually accumulating characteristics suddenly make possible a whole new level of complexity -- a level that seems to just ... emerge.

Darwin had this really great idea, and people added to it later on
[...] but there are phenomena that don't fit within the basic framework. The modern synthesis fits really well with some processes, and with others might not be the full picture.

The tenet of the modern synthesis is that gradualism arises from the cumulative effects of mutations. Most mutations are bad; some are good;
and you sum them up over time and things gradually improve. This can explain much of the patterns we see around us -- but one very interesting concept that is not fully encompassed by gradualism is the concept of pre-adaptation.

Mary Jane West-Eberhard studies the role of development and plasticicity in evolution ... how some changes, it seems like they bring something to the table in a new way that wasn't selected at the level of phenotype. Pre-adaptation is a change that occurs in the past, that's a good thing, and can be explained through gradual change ....
but when you encounter some kind of new context, it springs you forward.

[As for my own work] ... the worker behavior of honeybees. They're one example of the superorganism. They have a very intriguing division of labor. That's one of the hallmarks of superorganisms: individuals do different things, like organs in the body. An organ is different from another organ in the context of the body. The division of labor in honeybee workers is between bees in the nest and those out foraging.
And between foragers, there's specialization of a bee collecting a mixture of pollen. Just as people can do different jobs, based on interest, these bees are doing very different things.

We published an alternative [theory of their] evolution, deriving from pre-adaptations. ["Complex social behaviour derived from maternal reproductive traits," published in Nature in 2006.] We proposed that the division of labor between worker honeybees that prefer nectar or pollen is a pre-adaptation that came from the solitary life cycle of the bee. So that's a specific example of how evolution can throw up a new pattern into play: you have an ordinary life cycle in the individual, but in a social context it's exploited by the colony to create bees that are experts in different things.

The transcription doesn't do justice to this part of Amdam's explanation. To boil it down: in nature, solitary honeybees go through multiple reproductive stages, each characterized by a particular physiology. In hives, individual bees are suspended at particular reproductive states -- that's how specialization occurs -- and their state is determined by interaction with other non-reproducing members of the hive.

The neo-Darwinian framework ... you can think of it as a linear process. But here it's nonlinear. You set something up in a linear sense -- the reproductive cycle of a female. When the females come together, the reproductive cycle is already there and can be used to create specialists. Then change is not linear anymore. Synergy is the wrong word; preadaptation is the right word. [It] enables you to make a step forward without this linear trajectory.

Division of labor is a completely different concept than reproduction.
[The jump] from reproductive cycles to divisions of labor is not just reproduction in a different context, some kind of single step forward.
It's an entirely new way of living, a whole new life history.

Until recently it was believed that the division of labor was an evolutionary development, that there were genes controlling for the division of labor. When they sequenced the honeybee genome, there was a big disappointment when they couldn't find any. [...]

In population-level selection, you have to define the unit of selection. In the case of honeybees and ants, it's the level of the colony. It's the colony that succeeds or fails, and is made up of individuals that contribute to success or failure, but it's selection at the colony level that guides it.

When you define the colony as the unit of selection, you have the superorganism at the level of individual, and you can explain its changes through the change of its parts. That's similar to any gradual process. The leap ... comes in at the founding of the colony, in how you build this new phenotype, in the emergent phenomena of social life or a colony. This is a big leap forward in evolution. When it's become a stable entity at the level of population, then the neo-Darwinian framework is perfectly matched to how it's changing through time -- but when you go from solitary living to a social being, and you use evolutionary building blocks or old genetic networks to rapidly build a new phenotype in which [genes governing individual processes form the basis of] a social division of labor ... that's where the gradualism of neo-Darwinism is not the perfect match.

A possible application of Amdam's thinking: cancer research.

Image: Todd Huffman

• A Brief History of the Superorganism, Part One
• A Brief History of the Superorganism, Part Two
• Thoughts on Ants, Altruism and the Future of Humanity
• Is Homosexuality an Evolutionary Step Towards the Superorganism?
• Honeybee Weapon in War on Cancer
• Life's Complexity Began With Poop
• Complexity Theory Takes Evolution to Another Level
• Evolution as Biological Thermodynamics

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