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The presence of exposed land on the early Earth is a prerequisite for a certain type of prebiotic chemical evolution in which the oscillating activity of water, driven by short-term, day–night, and seasonal cycles, facilitates the synthesis of proto-biopolymers. Exposed land is, however, not guaranteed to exist on the early Earth, which is likely to have been drastically different from the modern Earth. This mini-review attempts to provide an up-to-date account on the possibility of exposed land on the early Earth by integrating recent geological and geophysical findings. Owing to the competing effects of the growing ocean and continents in the Hadean, a substantial expanse of the Earth’s surface (∼20% or more) could have been covered by exposed continents in the mid-Hadean. In contrast, exposed land may have been limited to isolated ocean islands in the late Hadean and early Archean. The importance of exposed land during the origins of life remains an open question.
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Colonizing the Caribbean: New geological data and an updated land‐vertebrate colonization record challenge the GAARlandia land‐bridge hypothesis
Abstract Over the past three decades, the hypothesized mid‐Cenozoic GAARlandia walkway (34 ± 1 Ma) has featured prominently in discussions on Caribbean biogeography. However, a fundamental issue has been a lack of geological and geophysical data from the Aves Ridge with which to evaluate the proposal. Consequently, opinions have been based purely on biological data, mainly from molecular‐clock studies but also from fossils and taxonomic composition. For whatever reasons, a polarization of views has occurred; some champion the land‐bridge to explain the colonizations of the island group, whereas others prefer over‐water dispersal. We examine the hypothesis drawing upon an updated compilation of land‐vertebrate colonizations (35 clades: 6 amphibian, 6 mammal and 23 reptile) plus a newly published geological study of the Aves Ridge and the adjacent Grenada Basin (to the east). The former indicates that the colonizations were heavily filtered and assembled in a piecemeal fashion consistent with over‐water dispersal; a mid‐Cenozoic ecological corridor would likely have led to a richer assemblage with a wider variety of components. The latter, which draws upon drill‐core and seismic data, indicates that the southern and central Aves Ridge was submerged at the aforesaid time. With the GAARlandia hypothesis geologically falsified, many biogeographical scenarios that have been proposed for the Greater Antillean biota now require re‐evaluation.
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- Award ID(s):
- 1932765
- PAR ID:
- 10367644
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 48
- Issue:
- 11
- ISSN:
- 0305-0270
- Page Range / eLocation ID:
- p. 2699-2707
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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