Punctuated Equilibrium Example: A Marine Microfossil

The paper

Spencer-Cervato, C. and Thierstein, H.R., 1997. First appearance of Globorotalia truncatulinoides: cladogenesis and immigration. Marine Micropaleontology, v.30, p.267-291.
reports on the species Globorotalia crassaformis. There is a location in the South Pacific where this species gradually turns into a transitional species, G. tosaensis, and then into G. truncatulinoides. The gradual change took 500,000 years.

In the Indian and Atlantic oceans, in slightly more recent sediment, we find the "sudden" appearance of the descendant species. This "suddenness" is therefore from migration, not Creation.

We know that these are different species (and not just strange looking fossils of a single species) because both species still exist today.

Thanks to geologist Dr. Andrew MacRae for this example.

Last modified: 6 August 1997

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