Abstract
Artificial life studies life-like organisation across substrates. The standard bottom-up taxonomy distinguishes physico-chemical, physico-mechanical, and computational substrates (Stepney, 2025), and classifies where an artificial organism appears. A recent overview of virtual artificial life (Stepney, 2025) concludes that virtual systems satisfying the full requirements of life (autopoiesis, agency, and open-ended adaptation) have not yet been exhibited, and identifies thermodynamic abstraction and the brittleness of symbolic substrates as recurrent limitations. We argue that an axis orthogonal to the standard taxonomy has remained underspecified: the causal role of the computing substrate itself. We propose substrate-coupled artificial life (SCAL) as a research programme in which the physical dynamics of the substrate participate causally in the production, persistence, and adaptation of life-like organisation, rather than serving as an inert execution layer. The framework is grounded in three observations about conventional silicon: 1/f noise from charge-trap dynamics at MOSFET interfaces, a cache-hierarchy latency gradient that satisfies Lewontin-style criteria for differential persistence among self-reinforcing memory-topology structures, and DRAM operating far from equilibrium as a Prigogine-class dissipative structure. We specify the experimental requirements such a programme implies in conventional silicon and set out specific falsification criteria. The work is theoretical and pre-experimental: it defines the framework, identifies the experimental commitments required to test it, and specifies the conditions under which it would fail.