Human hallux

(writing in progress)

Although humans differ from other vertebrates in many ways, there is no single diagnostic feature which distinguishes Homo morphologically from all other animals.

A unique feature of humans that seems previously to have been overlooked is that the longest digit on the hind foot (i.e. the pes) is the first digit (i.e. the hallux or ‘big toe’).

In all other mammals, including our closest relatives among the primates, the first digit of the foot is – if present at all – always shorter than at least one other hind digit.

The relative development of the hallux distinguishes humans categorically from all other animals, in a way that the thumb (i.e. the pollex)
does not.

Although humans have extreme manual dexterity, the hand is morphologically similar to the primitive manus of the first amphibians, and many animals (including not only primates but also rodents and birds) share some measure of opposability of the first digit with the rest of the fore foot (i.e. the manus).

Morphologically more diagnostic of humans than the thumb is the corresponding digit on the hind foot, one crucial to the upright bipedal running of humans.

At a behavioural level the ability of humans to run upright on two legs is unique (although many birds run bipedally, none of these maintain an upright spinal column while running) and at the simplest morphological level this depends on the length of the hallux, making the ‘big toe’ in a sense the quintessential part of the human body.

The reason why the diagnostic significance of the hallux has previously been overlooked by biologists is a cultural bias in which hands have been assumed to be both aesthetically and evolutionarily superior to feet.
 
(writing in progress)

Posted on June 14, 2022 12:52 AM by milewski