Muons penetrate much further than X-rays, they do essentially zero damage, and they are provided for free by the cosmos.
Image credit: Science Source/Digital Globe.
Contributed by Janet Franklin, September 15, 2015 (sent for review August 18, 2015; reviewed by Betsy Carlson and Ross D. E. MacPhee)
Significance
A flooded sinkhole cave on Abaco (The Bahamas) has yielded the richest (95 species) set of late Pleistocene (ice-age) vertebrates on any Caribbean island. We track changes in species composition on Abaco through time and relate those biotic changes to climate change. The warmer, wetter climate and rising sea levels from 15,000 to 9,000 years ago probably led to the disappearance on Abaco of at least 17 species of birds. Another 22 species of reptiles, birds, and mammals persisted through those environmental changes but did not survive the last 1,000 years of human activity. For the species that remain, we believe that direct human activity threatens their future more than climate change.
Abstract
We report 95 vertebrate taxa (13 fishes, 11 reptiles, 63 birds, 8 mammals) from late Pleistocene bone deposits in Sawmill Sink, Abaco, The Bahamas. The >5,000 fossils were recovered by scuba divers on ledges at depths of 27–35 m below sea level. Of the 95 species, 39 (41%) no longer occur on Abaco (4 reptiles, 31 birds, 4 mammals). We estimate that 17 of the 39 losses (all of them birds) are linked to changes during the Pleistocene–Holocene Transition (PHT) (∼15–9 ka) in climate (becoming more warm and moist), habitat (expansion of broadleaf forest at the expense of pine woodland), sea level (rising from −80 m to nearly modern levels), and island area (receding from ∼17,000 km2 to 1,214 km2). The remaining 22 losses likely are related to the presence of humans on Abaco for the past 1,000 y. Thus, the late Holocene arrival of people probably depleted more populations than the dramatic physical and biological changes associated with the PHT.
Footnotes
- ↵1To whom correspondence should be addressed. Email: janet.franklin{at}asu.edu.
Author contributions: D.W.S., N.A.A., and J.F. designed research; D.W.S., B.K., and J.F. performed research; D.W.S., J.I.M., J.A.S.-C., H.M.S., and J.F. analyzed data; and D.W.S., N.A.A., J.I.M., J.A.S.-C., H.M.S., and J.F. wrote the paper.
Reviewers: B.C., Southeastern Archaeological Research, Inc.; and R.D.E.M., American Museum of Natural History.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1516490112/-/DCSupplemental.
Vertebrates on an ice-age Caribbean island
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- Ecology
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