Sci&Tech Editor Georgia Brooks explains the exciting new interdisciplinary theory, and its potential to unite discourses and explain unsolved scientific problems.

Written by Georgia Brooks
Images by Zoltan Tasi

Physics, as a scientific theory, manages to explain many things (and fails when it comes to a fair few). Scientists for years have been attempting to reconcile the laws of physics as we understand them now, with biological explanations of evolution. An international and interdisciplinary team of scientists have come up with a potential solution: Assembly Theory

Darwin’s theory of natural selection states that the evolution of species occurs when random variations in genetics become selected for survival over the course of generations. However, quantitative explanations of natural selection tend to focus on outcomes, and do not take physics into account. 

Where Assembly Theory is different, is that rather than defining matter by the materials that make it up (as we tend to do), it defines objects by the possible steps or ‘formation histories’ that the object underwent to reach where it is. This gives objects a dimension of time that isn’t taken into account when we just consider them in terms of the ‘stuff’ that makes them up. 

Rather than defining matter by the materials that make it up, it defines objects by the possible steps that the object underwent to reach where it is.

The scientists created a quantity called ‘assembly’ from two variables: 

  • Assembly index: the minimum number of steps needed to produce an object
  • Copy number: the number of this object in the world

Combined, these variables give an equation which can be used to determine the amount of selection that was needed to create this object. The idea of selection is reflected in the equation: an object with a high assembly index and a high copy number is evidence of selection. In simpler terms, for there to be a lot of something that is relatively complex to create, there must be some sort of advantage to it. 

Currently the theory has only been developed to the extent of molecules – expanding this would be far more complex

This theory unifies physics (the processes) with biological selection (the outcomes), providing a new framework with which to view both disciplines. There is also the potential for experimentation to determine the assembly index of a molecule, which would allow the theoretical calculations to be checked. However, currently the theory has only been developed to the extent of molecules – expanding this to the scale of organelles, organs and organisms would be far more complex, but could have huge scientific implications. 

Right now, Assembly Theory is an incredibly general framework. This is what allows it to potentially explain causation, evolution and other biological processes. Scaling the concepts to be applied more usefully within biology and beyond will take a lot of refinement and further research. Despite this, the implications of applying a temporal frame to these disciplines must now be taken into account when it comes to defining and understanding matter. Although it requires considerable refinement, there are plenty of research avenues open, and assembly theory provides a potential means to unify the scientific disciplines further.

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