Different elements of the fogey book vanish at different charge per unit : os is lose at greater charge per unit than terrestrial deposit , and that ’s specially the fount for the continental U.S. and South America , compared to the Arctic . The finding were published inBiology Letterslast week .
When it amount to the fossil criminal record , older thing are generally less common than youthful things . This progressive , time - dependent expiration of geological deposits is called taphonomic loss . And to make certain copiousness is mensurate as actual teemingness in the fogy record for a particular time period ( relative to the abundance of geologic deposits of the same age ) , researchers turn to what ’s called taphonomic correction .
To create theoretical account of taphonomic loss , University of Wyoming’sTodd SurovellandSpencer Peltoncompiled hundred of carbon 14 dates on bones of extinct Pleistocene fauna from South America , the contiguous U.S. , and easterly Beringia ( near the Bering Strait between Russia and Alaska ) that go steady back to between 13,000 and 40,000 years .
The duo notice that bone is lost at great rate than terrestrial sediments overall – but only for South America and the non - arctic regions of the U.S. Bone in eastern Beringia was lost at approximately the same rate as terrene deposit , thanks to the excellent saving event of permafrost . “ well more ivory has been fall back over meter in region further south – in fact , at a faster rate than the sediments in which they were deposit have gnaw at , " Surovell articulate in astatement . " That mean investigator must set for those differences as they estimate the number of these beast , many of which are now out , across the Americas . "
For the 10,000 - twelvemonth point from 25,000 to 15,000 years ago , their eastern Beringia bone model designate an approximately 47 percent loss of material , while for the South America and contiguous U.S. finger cymbals , their theoretical account find a 93 to 99 percent loss . That means , 100 fossils date back 25,000 years from Alaska would be tantamount in abundance to about 189 fossils date back 15,000 years ; for South America and farther south in the U.S. , 100 25,000 - class - honest-to-god fossil are equivalent to more than 3,000 fossil at 15,000 years before present .
