Evolution: only genetics can design a bush of life (Introduction)

by David Turell , Wednesday, June 26, 2019, 18:57 (1976 days ago) @ Balance_Maintained

There is great difficulty in staying with the Linnaeus classification based only only body appearance:

https://www.quantamagazine.org/phyla-and-other-flawed-taxonomic-categories-vex-biologis...

"The problem that Hejnol sees with the whole system is that the ranks don’t mean anything specific or uniform across all groups of life. Even though species is arguably the most important rank across multiple fields of biology, there are dozens of species concepts in use — and biologists working with different groups of organisms can’t seem to agree on just one. You might think that the other end of the hierarchy would be more settled, but it wasn’t so long ago that domains simply didn’t exist — the three domains we use today (Archaea, Bacteria and Eucarya) were only proposed in 1990. At that time, the top rank was kingdom, and there were five of those; now there are at least six, though some say there should be as many as 32. Similar ambiguities plague all the taxonomic ranks in between — even those often considered to be major, distinct and unambiguous, like phyla.

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"Over time, the number of animal phyla has expanded to about 35. Yet there has never been a solid definition for what makes a group a phylum as opposed to a subphylum, a class or any other taxonomic rank. There have been many arguments about whether groups like vertebrates or nematodes are distinctive enough to be their own phyla, or whether phyla like arthropods, tardigrades, velvet worms and annelids should be lumped in with others (as they were in Haeckel’s day).

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"But perhaps a bigger problem than the artificiality of the boundaries between phyla is that they also tell us little about the range in diversity within a phylum. Some, like the phylum Placozoa, have almost no morphological diversity: All placozoans look so much alike that researchers haven’t yet decided whether there are only a handful of species or more than a hundred of them.

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"Even if phyla were defined on the basis of evolutionary timing, deciding which point in the evolutionary process to use would still be arbitrary and anthropogenic. “If you want to be consistent,” Jenner said, each rank would have to be tied to an evolutionary split and would contain only sister groups — so there would be two phyla, and then two subphyla from each of them, and so on. But that’s impractical too, according to Jenner, because it would mean that everything that isn’t a sponge belongs in one phylum. “Nobody would say that’s a good idea.”

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"... searching for the unique characteristics that define Linnaean ranks is “wrong evolutionary thinking.” Hejnol and his colleagues not only found flaws in the statistical analyses used in that study, but also discovered a more fundamental error: the conflation of current patterns with the processes that led to them. Notable differences between individual species within phyla are to be expected because each lineage developed independently over hundreds of millions of years. That tells us almost nothing, though, about how the lineages originally split.

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"In the end, there simply seem to be no objective, consistent criteria by which to define a phylum — or any other rank, for that matter. “So far, all explanations of what a phylum is have badly failed,” Hejnol said. “This is not a scientific entity which we can use, or should continue to use, when we communicate with each other.”

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"Scientists can usually sidestep the problems with taxonomic rankings by separating discussions about how organisms evolved from arguments about how to name or classify them. “When you’re doing evolution, you’re doing evolution. And when you’re doing systematics and taxonomy, that’s a different thing,” he said. That separation may be awkward, but “it’s clunky because life is clunky.'”

Comment: I still feel this is the wrong approach. Use genetic comparisons as previously proposed. God made a complex bush obviously to purposely to create the necessary econiches for a food supply to finally reach primates and then humans over 3.8 billion years. God chose the entirety of the evolutionary process of creation.