The way in which to define the term “diaspora” depends on the depth of the historical perspective from which the migration of humans across the face of the Earth is approached. Diasporas – intentional relocation of a group of people united by similar physical characteristic or a common country of origin – have been occurring since before the dawn of written history.
Even prior to the genesis of the modern human species, evolutionary predecessors traveled large distances to colonize the corners of the globe. It is not as if ancient humans all independently came into being on the landmasses on which people reside today. Rather, noting how the continents have spread out over millions of years, it is believed individual diasporas took the earliest members of the Homo sapiens family-group off of Africa some 150,000 years ago.
The diaspora to the Americas is much newer. Depending one’s school of thought, migrations to the New World may have been as recent as 20,000 years ago. Still after these prehistoric mass migrations, diasporas would continue, including the proliferation of early peoples like the Vikings.
Nonetheless, more commonly, a diaspora is seen as narrower in scope than a migration. Diasporas are generally considered different from migrations in that diasporas are usually a forced relocation at the hands of another; this is why the above periods of travel from continent to continent are usually referred to as migrations.