The title of this post are two common remarks one hears when the press covers evolution. Drives me straight up the wall. A study published in the Proceedings of the Royal Society B looks at these claims from the standpoint of paleontology and paleoanthropology.
The study examined the record of fossil discoveries in catarrhine primates and non-avian dinosaurs to assess the impact of fossil discoveries on our understanding of those groups evolutionary history.
As the authors put it:
Sampling theory predicts that the majority of new species are discovered rapidly and that the rate of discovery slows to an asymptote as sampling matures. Given this, it is expected that as species are discovered our knowledge of the fossil record of higher taxonomic groups should improve to the extent that new discoveries merely fill previously known gaps rather than identifying entirely new (and previously unknown) clades. Secondly, the phylogenetic distribution of newly discovered taxa should be random and so, again, existing phylogenetic patterns should be robust to the discovery of new taxa.
Thirdly, in consequence, macroevolutionary hypotheses based on mature datasets should remain robust to continued discovery of species.
More importantly, how can you tell when you tell whether your group is robust to future discoveries? The authors examined the phylogenies of catarrhine primates and non-avian dinosaurs with regard to changes in the quality of the fossil record through time, changes in tree shape, and diversification rate shifts. They conclude that future discoveries will have minimal impact on our understanding of catarrhine primate evolutionary history and could have a significant impact on our understanding of the evolutionary history of non-avian dinosaurs.
Tarver et al conclude:
Ultimately, our study indicates that the stability of taxonomic datasets should be assessed before embarking on macroevolutionary studies, or else researchers run the risk of conflating artefacts of incomplete taxonomic, stratigraphic, ecological or biogeographic sampling for evolutionary phenomena. This may provide fewer headlines and knowledge of evolutionary history that stands the test of time.
One of the ironic things about this is that a different paper also coauthored by Benton received just such hyperbolic treatment in the mainstream media.
Update 1: I have fixed the link and formatting issues. I published this post via email and, oddly about half of it has disappeared. I will fix that issue this evening.
Update 2: The missing text has been added back in.