Evolution in the News - April 2021
by Do-While Jones

Dinosaur Leg Bones

The evolution of dinosaurs is based on shapes of leg bones.

In this month’s feature article, we alleged that evolution is based entirely upon perceived similarity, so here’s a recent example from the professional literature which proves our point.

Bipedal locomotion evolved along the archosaurian lineage to birds, shifting from “hip-based” to “knee-based” mechanisms. However, the roles of individual muscles in these changes and their evolutionary timings remain obscure. Using 13 three-dimensional musculoskeletal models of the hindlimbs of bird-line archosaurs, we quantify how the moment arms (i.e., leverages) of 35 locomotor muscles evolved. 1

They looked at nothing other than hip, leg, and foot bones. They didn’t consider teeth or ribs or anything else. They just took lots of measurements of bones and made calculations.

Based on all those measurements they came up with an evolutionary history represented by the following two diagrams.

Don’t worry if you can’t read or understand the diagrams because it doesn’t really matter what these diagrams show. Our purpose is just to show the kind of drawings they made, based on the measurements and calculations, and that they drew conclusions from these diagrams.

We won’t waste time disputing the accuracy of their measurements or their method of calculating similarity because they are irrelevant. Our point is that they determined relationships based upon nothing more than the similarity of bones (from which they inferred muscle attachments, in the cases of extinct species). They said,

This inference also depends on the (parsimonious) assumption of a continuous spectrum between hip- and knee-based locomotion without apomorphic intermediate states, which is yet to be tested via quantitative biomechanical analysis. 2

The definition of parsimony is,

The scientific law of parsimony dictates that any example of animal behavior should be interpreted at its simplest, most immediate level. 3

They made objective measurements and precise calculations, but in the end, they accepted what they subjectively considered to be the simplest conclusion that confirmed their bias. (And, by the way, they need more money for future research to test their conclusions. )

We know from experience that future evolutionists will make equally accurate measurements of teeth, or cranial volumes, or rib cages, and compute equally valid mathematical assessments of similarity which will show different evolutionary histories. As we hope you learned by doing the experiments suggested in this month’s feature article, future evolutionists might even compute different degrees of similarity from the same measurements of hip and leg bones.

Not only is similarity subjective, it isn’t proof of common ancestry.

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1 Science Advances, 19 March 2021, V. R. Allen, et al., “The evolution of pelvic limb muscle moment arms in bird-line archosaurs”, https://advances.sciencemag.org/content/7/12/eabe2778
2 ibid.
3 https://www.merriam-webster.com/dictionary/parsimony