Research help: how many species have there been?

As proofreading goes on chapter by chapter, I get my last chance to review references and properly site cite sources. It’s slow, tedious, and so little fun, I thought I’d throw some of it at you.

The question: How many species in the history of the planet have gone extinct?

The web has been surprisingly stingy. The wikipedia entry for extinction pointed me back at mediocre sources I already had.

Obviously I don’t need hard data as there isn’t much: but a ripe quote from an expert, or a summary of expert opinions would be perfect.

The prize: find me a reference that I’m willing to use in the book, and I’ll put your name in the book’s acknowledgments.

12 Responses to “Research help: how many species have there been?”

  1. bbz

    I found lots of info about how many species exist now, but only one about how many ever existed. So the estimate is 200 million to 1 billion and up. Thanks for the challenge.

    “Extinction is part of the natural process of evolution. The one and a half million species, which are now conservatively estimated to exist, represent less than one percent of the total number of species ever present on this planet (Nei, 1975).” (1)

    2 – 100 million species exist today. (2)
    4 – 6 million ” (4)

    “Between about 1.5 and 1.75 million species have been discovered and scientifically described thus far (LeCointre and Guyader, 2001; Cracraft, 2002).” (and more gold from there) (3)


  2. Scott (admin)

    Behold the power of blogs! Thanks John, nicely done.

    Anyone think they can top that?

    1. Ken Burroughs

      Well if 99.9% of species that have ever existed are extinct and we have between 10 – 100 million species now conservatively then there have been about 500-600 billion species.

  3. Robin

    I just read about the “All Species Foundation” at Kevin Kelly’s website a few days ago. “The organization would catalog very living species on earth within one human generation (25 years).”

    Maybe the following information could help you:
    “Estimates of undiscovered species on Earth range from 10 million to 100 million and The US National Science Board ( 1989) predicted that as many as 25% or more of the Earth’s species may become extinct by 2014”

    kind regards,

  4. Sam Greenfield

    I recommend citing sources rather than trying to “site” or even “sight” them. :-)

  5. Scott (admin)

    Sam – what are you trying to get mentioned in the book as a wise-ass or something? :)

  6. Mikko Heikkinen

    Few estimates/guesses on the amount of species that have existed:

    G. G. Simpson 1952: How Many Species? Evolution, Vol. 6, No. 3, p. 342
    50-4000 million species

    A. Cailleux 1954: How many species? Evolution vol, 8 p. 82-83
    17-860 million species

    Estimates on the amount of species living vary between 5 to 50 million, according to J. E. Winston 1999: Describing Species (and its references). About 1.4 million of those are known to science.

    Few other references that might help but which I don’t have access to:

    A. S. Iberall 1989: How many species? GeoJournal Volume 18, Number 2 / March, 1989

    D.M. Raup 1986: Biological extinction in Earth history. Science 231,1528-1533

  7. Peter Montgomery

    One more note
    Headline: MOST of the species that have ever existed do NOT exist today.

    Details: Due to the half dozen major cataclysmic events in the Earth’s history, there have been several times (such as 65 million years ago), when MOST of the Earth’s species have been eliminated. These major events go back to life’s early roots. 2+ billion years. This is in addition to the normal processes for evolution / mutation which cause species die-off.

    (without citation I’m afraid). -Peter

  8. Susan

    Don’t forget the bugs!

    “Insects make up 80 percent of all known animal species. Though only 900,000 insects have been identified, experts agree that there are still vast numbers of undocumented species. Estimates vary, but some researchers believe that as many as 2 to 100 million insect species could exist.”

    And the plants!

    “About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet’s species. Less than 5 percent of the animal species in the seas survived. On land less than a third of the large animal species made it. Nearly all the trees died.”

  9. Bruce Hughes

    I would recommend you start in the Back Matter of Edward O. Wilson’s “the Diversity of Life”, which you can search on Amazon.


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