In theory, as technology becomes more and more advanced, you can have enough specialists to fill a very large number of very deep supply chains.
When you have a primitive society, you just need a "wood guy", a "stone guy" and a "plants guy".
If you want to have fancy computers, you need things like "high pressure silane pump control loop guy".
Though I'm pretty sure the number of people needed to maintain the current level of technology is substantially less than 7 billion, because a lot of those people are stuck in subsistence farming and basically don't contribute to industry.
When you have a primitive society, you just need a "wood guy", a "stone guy" and a "plants guy".
If you want to have fancy computers, you need things like "high pressure silane pump control loop guy".
Though I'm pretty sure the number of people needed to maintain the current level of technology is substantially less than 7 billion, because a lot of those people are stuck in subsistence farming and basically don't contribute to industry.