A real man ENDS a fight, he doesn't START one
Without cheap access to space, the future of mankind is environmental degredation, shorter lifespans, poor standard of living, and much misery.
Even today we can see the results of environmental degredation if we dare look. Compare, for example, the typical American home of 2003 compared to the typical American home of 1903. The typical American home of 1903 was built using large long timbers and thick boards and studs (1903's 2x4's were really 2" by 4" in size, unlike today's 2x4's, which are smaller). The attic was framed with 2x8 or 2x10 joists and 2x6 or 2x8 rafters of 20' or longer in length. The sheathing was diagonal planks 1" in thickness, topped by wooden siding 1" in thickness. The interior walls were plaster applied to 1x2 wooden lathe.
The typical home of today is built almost solely with short sticks of wood, wood chips, and glue. The attic is built of pieces of 2x4 held together with pressed-on metal plates to form trusses, and 'truss uplift' is normal and expected in the home of 2003 ('truss uplift' is where the ceiling moves due to the differing environment between top and bottom of the trusses, causing the joint between ceiling and wall to crack). Floor joists for a second floor are built out of 2x4's using truss techniques too. The few large beams are built out of strips of wood glued together ("glulams"), rather than being large solid pieces of wood. The decking, rather than being 1" flooring over 1" diagonal deck, is 5/8" of wood chips held together by glue ("oriented strand board"), with the carpet applied directly on top of it. The sheathing is 1/2" of wood chips held together by glue, and is applied only where absolutely necessary to provide the minimal racking strength required by law, on most of the house the siding is applied directly to 15# asphalt-impregnated felt stapled to the studs. The biggest piece of lumber in the whole house is 8' long 2x4's, which are used to piece together everything else.
What happened in that hundred years? Resource depletion, that's what. Big timber became expensive. Thus new American houses are built out of sticks and sawdust and glue.
What will the typical new American home look like in a hundred years? Well, if we extrapolate the trend from 1903 to 2003 all the way to 2103, they will be made of cardboard stiffened with spit.
Without access to the resources of the Solar System, the future of humanity is to slowly wind down until we lack the capability to leave our little island, much less sail elsewhere and create new outposts where hopefully some sort of civilization will survive after ours collapses.