I agree that it became more formalized in recent history - but it has existed in a general form for a long time. I would consider labour to be any work done fo

I agree that it became more formalized in recent history - but it has existed in a general form for a long time. I would consider labour to be any work done for a wage - exchanging your work for payment from someone else... And that has been going since Sumeria at least - probably a long time prior to any written record we can consult. That said, the proportion of the population participating in the labour market has changed - right now nearly all adults participate in the labour market in some manner, but subsistence farming as the norm for life wasn't so far back in history.