Journalist Tom Bethell writes to ask:
Reptiles exist in the same way that invertebrates exist. The problem arises for both groups when the are said to be ancestral to some other group. As in this 4-word sentence:
“Vertebrates evolved from invertebrates.”
It is an (inconspicuous) assertion that vertebrates evolved. Back-up evidence is seemingly provided by naming the ancestral group: Invertebrates.
But it doesn’t take a genius to see that the ancestral group is (improperly) defined by the absence of the character that defines the descendant group. What appears to be a factual statement with evidence attached turns out to be a truism. Rewriting it more plainly:
“The first vertebrate had parents that were not vertebrates.” (Duh.)
This was pointed out some years ago by the late Colin Patterson, chief paleontologist at the Natural History Museum in London. Patterson then boldly went on to say that ALL ANCESTRAL GROUPS ARE DEFINED BY THE ABSENCE OF CHARACTERS. Which characters? Those that define the descendant group.
An influential group of systematists called Cladists drew attention to this problem. Patterson was supported by some paleontologists at the American Museum of Natural History, notably Gary Nelson (Ichthyology) and Norman Platnick (one of the leading experts on spiders). The founder of cladistics was Willi Hennig, from East Germany. He called groups “defined” (i.e. ill defined) by the absence of character “paraphyletic.”
How does this apply to reptiles? They are ill-defined in the same way.
There is a broad group of organisms defined by the presence of an amnion, an envelope that shields early cells in the development of the organism. These organisms are called amniotes. Among them are two well defined groups: Birds and Mammals. But there are other amniota that are neither birds nor mammals. These are the ones we call reptiles. So they are non-mammalian, non-avian amniotes.
Therefore (problem solved) reptiles — non mammalian, non avian amniota — are ancestral to birds and mammals.
Aristotle called such ill defined groups confused and the cladists supported Aristotle. The function that such groups play in evolutionary theory is to serve as ancestral groups, thereby seeming to confirm Darwinism. They tell us which are the ancestral groups in the “tree of life.” They occupy the nodes in that tree.
I believe that nodes in the tree of life are always empty. Can anyone falsify that?
But I believe the tree of life is itself a fiction, as Craig Venter pointed out at a conference at Arizona State Univ. in 2011. Dawkins was there and was flummoxed.
The same problem exists with apes. They are defined as non-human hominoids, So guess what are they said to be ancestral to . . .
The overall problem brought up by the Cladists was discussed at length by the late David Hull, in his book. Science as a Process (1988).
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