Something like that happens whenever there is a Genetic Takeover.

For example, probably at one point only one individual used DNA. Now all known life on Earth is descended from that individual – and all the RNA-based organisms have gone extinct.

In fact I can only think of one sense in which multicellular organisms dominate:

“A probably tiny initial lineage soon came to dominate the tiny tiny tiny tiny fraction of life on Earth that we humans find interesting to look at.”

What other single species has caused a mass extinction (except possibly, as you say, the first oxygen producer)?

The relevant inequalities, it seems to me, are not of genetic or even memetic fitness but of power, as vague as that is.

“total bacterial biomass (even at such minimal weight per cell) may exceed all the rest of life combined, even forest trees, once we include the subterranean populations as well”

- http://www.stephenjaygould.org/library/gould_bacteria.html

…but he offers no figures in support of this – and even if there were any, it would not support the assertion under discussion – since that refers to “unicellular organisms” and “orders of magnitude”.

http://en.wikipedia.org/wiki/Metagenomics

Sogin et al., http://www.pnas.org/cgi/content/full/103/32/12115

Venter’s work, e.g.: http://www.sciencemag.org/cgi/content/full/304/5667/66
; http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001456

Note that in the Sargasso Sea work (Venter Science reference), approximately as many or more proteins were sampled from the Sargasso Sea as had previously been known from all previous bacterial work.

The Sogin work is particularly straightforward and surprising: by the standard (though arguable) definition of species in bacteria, there is a shocking amount of bacterial diversity present in the ocean. We still don’t have a good upper OR lower estimate on the number of bacterial species, but every time we look at a new microbial niche we find 10s or 100s of thousands of different species.

The real problem, of course, is that this is an active area of research, so I can’t give you hard and fast numbers: the field of microbial diversity is still figuring out the broad outline of what is out there and what it means. Heck, “diversity” by any of the old definitions (16s RNA, for example) may be the wrong way to think about true diversity, because there’s at least some evidence that many of these bacteria don’t do radically new things. (Many of them do, of course, but many of them don’t .

–titus

To illustrate, if 1500 military export markets were well-developed, Zulu armies would certainly be cheaply kitted with firearms and stirrups by the time the British got round to visiting.

Tim, here’s a discussion of the biomass issue:

http://www.stephenjaygould.org/library/gould_bacteria.html

It seems pretty up-to-date. It’s tough to find good research-level discussions of this stuff because it’s in introductory textbooks in microbiology now, but Gould comes through!

From the perspective of diversity, we *know* that there are many more species and varieties of bacteria than any other type, class, or group of organisms; that’s been evident for well over a decade and has been confirmed most spectacularly by the recent metagenomic studies by (among many others) Venter and the JGI. (The only possible exception is viruses, which occupy an uncomfortable niche in the biological hierarchy.)

Gould says that plant biomass outweights bacteria, which is no doubt correct. Diversity-wise, however, bacteria are far more “successful” than animals or plants.

As for Robin’s generalizations — I think the emergence of multicellularity certainly counts as a dramatic singularity event! (As does the CNS, probably, if he ever properly dates it

–titus