If surplus population includes indigenous people including people with limited exposure to colonisation or capitalism,

How can the position ‘within capitalism’ be understood Their life is not within capitalism? And yet they experience and are affected by heteronomous forces

An Identical Abject-Subject:

The theory of surplus population derives from arguments presented by Marx in the first volume of Capital, chapter 25 in particular, on the “general law of capitalist accumulation”. Marx defines the surplus population as workers without regular access to work: a worker “belongs to” the surplus population “when he is only partially employed or wholly unemployed”.4 Marx refers to this surplus population as a “relative surplus population”, because these workers are not absolutely surplus, as in a Malthusian account (which is to say, it is not a matter of there not being enough food, water, shelter, etc). Instead, these workers are surplus relative to the needs of capital — that is, relative to capital’s demand for labour.