Assembly theory explains and quantifies selection and evolution Simplified

Darwin’s theory of Natural selection shows how selection among variants in the past generates current functionality, or past to present.

In theory, Physics can take us from past to current to future.

However, physics has no functional view of the Universe. This is why it cannot distinguish new functional features from random fluctuations.

Thus, true ’newness’ is impossible if we use either the physics or biology approach.

Therefore, we rely on randomness or statistics such as large combinatorial set of possibilities.

However, this search generates an unsustainable expansion.

Assembly Theory (AT) addresses these by describing how new features via selection works through the time aspect.

AT:

• predicts features of new discoveries during selection
• quantifies how much selection produced the current version without prespecifying individuals or units of selection.

In AT, living things are not considered as point particles (as in most physics). Instead, they are histories of their own formation as an intrinsic property, mapped as an assembly space* [which we will rename as historical evolution or HE].

The HE is the pathway that starts from elementary building blocks towards a living object, using only recursion.

For the shortest path, the HS captures the minimal memory.

• This historical memory has the minimal number of operations necessary to construct its current living thing from past things.

HE has ‘multiple realizability’ wherein biological evolution produces things with the same functions via “modular use of units” in many different contexts.

For each unit, the minimal HE is unique and independent of its formation. Therefore, it accounts for multiple realizability in how it could be constructed.

We introduce the foundations of AT and its implementation to quantify the degree of selection and evolution found in a collection of living things.

HE is a function of 2 quantities:

1. The number of copies of the observed living things
2. The living things HE indices

The HE index is the number of steps on a minimal path producing the living thing.

HE captures the amount of historical memory necessary to produce a resulting selected configuration of historically contingent living things.

• This is similar to how entropy quantifies the information (or lack of it) necessary for the configuration of particles.

HE is different because of its dependence on the contingency in construction paths of complex living things.

• HE leads to a unified language for describing natural selection.
• HE unifies selection across physics and biology.

A “living thing” is finite, distinguishable, persists, breakable into quantifiable elementary nonliving building blocks.

This definition is opposite to physics which treats fundamental things as unbreakable quantum particles.

We believe that fundamental quantum particles are not fundamental because they are really infinite particles limited by limited human observational ability.

Living things are anything that can be broken and built. This lets us account for the emergent living things produced by natural selection. This is fundamental to the theory.

‘Copy number’ has foundational importance in our theory that accounts for selection.

The more complex the living thing, the less likely an identical copy can exist unless some information-driven mechanism that generates that living thing is selected.

A living thing that has multiple copies allows the signatures describing the set of constraints that built it to be measured experimentally.

For example, mass spectrometry can measure assembly for nonliving molecules because it can measure how molecules are built by making bonds.

HE index and copy number

To construct an HE for a living thing, we take its elementary nonliving building blocks. Then we recursively join these to form new structures.

At each recursive step, the living things formed are added back to the HE pool, available for subsequent steps.

AT captures symmetry-breaking arising along construction paths due to recursive use of past living things that can be combined in different ways to make new things.

Assume object i. It is an HE that is produced by recursively assembled pathways from its nonliving building blocks. For each living thing, the most important feature is the HE index.

This index is the fewest steps required to generate the living thing from basic building blocks.