hard to say. i really don't know what you have in mind.

but if for some reason each human decided he/she would break ties with all other humans and keep to himself/herself to keep from putting something into "the system," i guess we might find examples of some fishermen eating well for a time, depending on their whereabouts (if they can labor for themselves in their environment within your hypothetical), but humankind wouldn't last too long.

is that what you're asking? if you have other ideas in mind and want to paint a picture, by all means. but can we agree first that humans are social creatures?

not sure exactly what you have in mind by “contribute labor” …

supposing you mean no one does anything to sustain life for himself/herself or others …

guess all the beautiful babies would be doomed to going feral and humankind wouldn’t last too long. we’re social creatures, ya know.

i guess what i’m saying is the other people’s labor isn’t the source of another’s entitlement, per se.

other people’s labor may contribute to material value of shared resources, but that labor doesn’t exist in a vacuum, and a little labor won’t eclipse the sun

just because the labor of other people may touch upon the bounty of our material world, to varying degrees, there are always other factors at play and society may not have relinquished more ancient claims from which all beautiful babies’ entitlement to UBI could be said to derive.

the world we’ve been born into has already been bought up prior to our arrival and with that fact comes the circumstance that those with established ownership rights lording over our shared reality must ask all the new borns to recognize property rights that will necessarily infringe those new borns’ freedoms to otherwise enjoy whatsoever they might like to make use of.

well a willingness to recognize property rights of others who have claimed dominion over the fruits of the land comes at a price - what we might call a universal basic income, or thomas paine would have referred to as a citizen’s dividend.

such a baseline social entitlement is even more appropriate in a modern world where much of the ‘labor’ comes from energy sourced from dead organic matter ie fossil fuels