The phrase “evolutionary success” sometimes appears in scientific productions. However, the concept seems to be based primarily upon quantitative data. For instance, Rodents are said to be “evolutionarily successful” because about 40% of Mammals are Rodents (about 2000 species out of 5000 Mammal species). In the same view, seed plants are considered “evolutionarily successful” because most modern-day plants produce seeds.
In this perspective, multicellular organisms are sometimes considered as having had little evolutionary success, if not being anecdotal, because they are hugely outnumbered by unicellular prokaryotes. As Gould stated: “We live now in the ‘age of bacteria’”.
Nevertheless, I was wondering whether such a vantage point was not biased. As a matter of fact, why consider that being successful necessarily means being numerous? There are no known animals able to run as fast as cheetahs: does that not make cheetahs evolutionarily successful? In a much more anthropocentric way, no known organism displays such a big brain as ours: does this make us a success of evolution?
Should we prefer qualitative assessments over quantitative ones?
Success doesn't necessarily correlate with numbers, as you say. Also, my opinion is that it is not evolution since no new species are being considered
Hello David; Whatever the phrase "evolutionary success" means, it surely is applied selectively and at different organizational scales. I generally read it to refer to a vague, impressionistic comparison of species diversity just as you have done. When I see it in the professional literature, it surely refers to diversity and, the editor should have insisted on using a diversity term.
As a picky note, humans don't have the largest brains. That distinction goes to elephants and cetaceans. We do have the largest brain/body mass ratio.
I agree with James Des Lauriers Evolutionary terms are too often used vaguely in publications to really mean things such as species diversity or adaptation
We don't have the largest brain/body mass ratio. We're in the top 10 or so, AFAIK, but the extreme is some species of mormyrid osteoglossiform which far surpasses us in that ratio and also in the ratio of brain/body oxygen consumption.
David; Thanks for the tip. As a result I looked up a paper by Nilsson (possibly your source as well) that confirms your assertion. Here is his bit that matters...
"Vertebrates have repeatedly been noted for having remarkably constant ratios of brain to body O2 consumption, the brain using 2–8 % of resting body O2 consumption, suggesting that evolution has put strict limits on the energetic cost of brain function. Only man, with a value of 20 %, is an exception to this rule. However, the results presented here suggest that, in the electric fish Gnathonemus petersii, the brain is responsible for approximately 60 % of body O2 consumption, a figure three times higher than that for any other vertebrate studied, including man. The exceptionally high energetic cost of the G. petersii brain appears to be a consequence both of the brain being very large and of the fish being ectothermic." The Journal of Experimental Biology 199, 603–607 (1996) 603 Printed in Great Britain © The Company of Biologists Limited 1996 JEB0101
More recently Sukhum (2018) develops the story further. Thanks, Jim Des Lauriers
In my opinion two concepts are relationship.For example Phylum Cnidaria is the first group of low metazoan invertebrates developed a coelenteron (=gastric cavity).The presence of it,is a evolutionary success quantitative because during the evolution this gastric cavity will be presents with differents names and with a complex structure through the animal evolution.The other hand, Phylum Cnidaria has cnidocyst and presence of it,is only and exclusive of this phylum,so it is do a evolutionary success qualitative.
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