To Simon and others:
The midtarsal restraining mechanism is a vague adaptation, but, in my opinion, a valid and important component of hominid evolution.
Herb Elftman, in about 1960 described this in rather non-scientific terms, in his simple and short paper (Elftman, 1960). One should recognise this as being incomplete, and lacking in scientific content, it was groundbreaking. Now, add to that some decent anthropological stuff; look at Straus, (1928), but far more importantly Pete Lisowski (1967)
and you begin to see real science. Pete, who I knew well, and died four years ago, was a world leader in talar morphology. His own mentor, Professor (later Lord) Zuckerman, emeritus of anatomy at Birmingham, said to his staff: “there is something funny about the talus – go and find it”.
Pete did a huge amount of work of angular changes in the primate talus (Lisowski, 1967). This paper has never had the recognition that it deserves – an outrage. While Pete didn’t make the connection between midtarsal function and the talar head torsion (why would he, he was an anatomist and a medical doctor), he was the first to note the peramorphic heterochrony, sometimes described as gerontomorphosis (taking the ancestral state, and accelerating it forwards), when compared to African Apes. This was a huge advancement back in 1967. What he noted for the first time was that the adult value of the ape, was the same As the infantile value of the human. This is incredibly important, and essentially not recognised in the podiatric world.
Look at the figures in either of your compulsory readings for this. You will see how the torsion of the head on the talus needed to be advanced in order to provide the obliquity of “axes” as described by himself. This has never been picked up on by any other writer, apart from myself.
Compare the bisection lines in humans and any other primate, and you will see a striking difference. Those that we associate with the st pronated state,
you will see in others in the st supinated state; but of course m/t mobility is the norm in non-human primates; they all have a normal m/t break. Always think in form and function.
Why was this ignored by Root et al? I suspect because they lacked a proper biological background. Ask yourself: how many podiatrists understand heterochrony, allometry, numerical taxonomy & other morphometrics, just to mention a few of the vital tools required to grasp fully the biological implications of shape changes in bone (or any other structures, come to that).
Elftman H (1960) The transverse tarsal joint and its control. Clinical Orthopaedics 16: 41-5.
Lisowski FP (1967) Angular growth changes and comparisons in the primate talus. Folia Primatologica 7: 81-97.
Required reading:
1992 Gradualistic evolution as expressed in the hominoid talus. The Journal of British Podiatric Medicine 48: 171-174
1993 The long arch: new thoughts on the evolution of an old structure. The Australian Podiatrist 27: 35-43
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