It has been far too long since my last post, occasioned by the fact that I have entirely too many irons in the fire.
I hope you will forgive this brief “drive-by” post, with a request for some help and information.
One of the common refrains that comes up regarding the fossil record, or regarding claims about biodiversity and the evolution of species more generally, is that the vast majority of species that have ever lived on the Earth have gone extinct. This is often phrased as “99% of species that have ever lived have gone extinct” or similar wording. (Occasionally someone will temper the number to 98% or 95% or some other nearby figure, but 99% seems to be the most common claim.)
I am trying to track down a credible source for this incredible claim.
With the help of, yes, Wikipedia, I’ve managed to make a little bit of progress.
- Apparently, in 1991, University of Chicago paleontologist, David Raup, estimated that there might have been anywhere from 5 to 50 billion species that had existed during the history of the Earth.
- Given then-current estimates of existing species, Michael McKinney calculated that “well over 99% of earth’s species” had gone extinct. As near as I can tell, this was presented by McKinney at a symposium and published in 1997 along with other symposium papers and presentations in a book titled, “The Biology of Rarity: Causes and consequences of rare-common differences”.
No doubt this is not the only source for this claim, as many other biologists would have quite readily drawn similar conclusions based on Raup’s estimate.
I would be most grateful for any additional, or more solid, sources for the idea that “99% of all species that have ever lived have gone extinct.”
Incidentally, it is worth noting that the actual number of known (not estimated or projected or inferred) species is quite different. Compared with some 1-2M known species currently living, there are about 250K identified fossil species. Obviously these numbers are also subject to some margin of error, but at least they deal with known, identified organisms, rather than projections and estimates. Even allowing for lots of gray area due to the ever-elusive definition of “species” and the fact that observable fossils will obviously tend toward larger creatures (e.g., one suspects it will be tough to get a decent count of bacteria in the fossil record!), it will still not be lost on the reader that these numbers flip the common claim on its head, with the fossil record count making up but a minor percentage of currently-living species, rather than vastly dwarfing the latter.
This leads to a couple of important follow-up questions:
- Is the fossil record truly so poor that many billions of species have come and gone without leaving a discernable trace? Not thousands, not millions, but billions? Were Gould and Eldridge wrong to suggest that the fossil record, albeit imperfect, is generally reliable and tells a largely accurate story of the history of life on Earth, at least as it relates to the larger animals?
- Or is the “99% extinct” claim serving some other role — perhaps something of a modern incarnation of Darwin’s proposal that the number of long-dead intermediates must be “innumerable” and that the fossil record is not to be trusted, because it reflects but a miniscule part of the Earth’s actual biological history?
I would like to know one way or another.
Any help you can give in either (a) tracking down good sources for the 99% extinct claim, or (b) spelling out why the claim should be accepted, despite the actual physical data, would be most helpful.