Without money you have a barter economy where “every day the shoemaker and the apple grower will have to learn anew the relative prices of dozens of commodities.”(Harari Pg. 176) This was a very unreliable system which led to the advent of a single currency, money. “Money is thus a universal medium of exchange that enables people to convert almost everything into almost anything else.”(Harari Pg. 179) As this system of currency spread and was developed in other parts of the world(using mainly gold and silver) this led to the peoples of afro-asia to conduct trade with one another leading them to be more unified.
Empires also lead to the unification of people. “An empire is defined solely by its cultural diversity and flexible borders.”(Harari Pg. 190) As Empires conquer more nations, cities and tribes over time these people are assimilated into the culture eventually becoming Roman when a few generations ago they were Carthaginian. Then when the empire inevitably collapses, and a new empire rises out of the ashes of the old one, and conquers other forieghn lands, the ideas of the new empire which were influenced by the old empire are passed along to new foreigners who become assimilated in the new empire, unifying a bigger part of the world through shared ideas.
And finally the other big unifier is religion. “The crucial historical role of religion has been to give superhuman legitimacy to these fragile structures.”(Harari Pg. 210) But has another aspect of unification besides being the glue for many political and economic systems in human history. As Paul of Tarsus though it “necessary to spread the good word about jesus throughout the world”(Harari Pg. 217) With this new universalizing nature of christainity and later islam the world would now be unified directley through religion regardless of empirical borders ore economic systems. By 1000AD Christianity or Islam had spread to all corners of the Afro-Asian world and today the Entire world. This is the final piece to the unification puzzle.
My own thoughts on Harari’s explanation to why humans are becoming more unifiers are quite uneventful as I agree with him on every level. Empires, Money, and religion are the 3 big pieces to unification as without one the others are less meaningful and impactful. And without one the world would be less unified. But even though he doesn’t say one is above the other I think money is the biggest unifier as even regions of multiple religions and empirical heritages will cooperate on the basis of money.