Equity isn't the only form of capital investment.
> How is capitalism different from early human tribes?
Well, lots of ways, including the thing that actually defines capitalism, the particular model of property rights.
> They also needed to work and trade.
Which is broadly true of every human society, regardless of politico-economic system; such systems differ in the (for instance) distribution of the accumulated benefits of trade, not in it's practical necessity.
> Things have become much more sophisticated but the basic principles remain.
The basic principles that remain the same are not the features that distinguish politico-economic systems from each other.
> People complain about spending too much time for a company and slaving away - but in earlier times they would have spend way more time on the fields plowing while 4 of their 8 kids died.
Yes, technology has improved since ancient times, and, in the domain of politico-economic systems even most critics of capitalism would agree that it represents positive progress from feudalism and other earlier politico-economic sysyems.