Divergences, Convergences, and Parallels

One way to conceive the shape of history is in terms of divergences, convergences, and parallels.

They occur at different scales of history.

In the history of the earth, one of the main divergences occurs when continents split apart by rifting. On several occasions in the earth’s past, supercontinents broke-up into smaller continents. Conversely, one of the main convergences occurs when continents amalgamate as their tectonic plates slide into one another. Parallels occur when some event such as an asteroid strike or a period of climate change brings consequences across the earth.

In the history of life, there is divergent, convergent, and parallel evolution. Divergent evolution is the predominant form, as once related populations evolve to become dissimilar and thus radiate into different lineages. Each major step in evolution was a divergence: the eukaryotes diverged from the prokaryotes, the multicellular diverged from the unicellular. Yet, there is also convergent evolution. This can occur when unrelated lineages move into the same environment. So, when land animals take to the sea, whether reptile, mammal, or bird, they evolve similar marine forms. Or, when ground dwellers take to the air, whether insect, reptile, or bird, they converge on similar forms. Parallel evolution is also important. Several different lineages appear to have independently evolved highly social arrangements, including ants and humans.

The shape of human history is, in large part, a matter of divergence, convergence, and parallelism. The greatest parallel was the about six or seven regions independently moved from foraging to farming in the space of a few thousand years. There have been many great divides as different populations diverged in forms of civilization, levels of technology, and degrees of wealth, among other divergences. Convergence is a late appearance in history as global linkages started making possible greater similarities across the world.

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