Philosophy Concordance - online philosophical quotations

HCF’s second argument against human adaptations for speech production is the discovery that the descended human larynx (which allows a large space of discriminable vowels, while compromising other functions) can be found in certain other mammalian species, where it may have evolved to exaggerate perceived size. HCF note that while a descended larynx “undoubtedly plays an important role in speech production in modern humans, it need not have first evolved for this function” but may be an example of “preadaptation” (in which a trait originally was selected for a function other than the one it currently serves).

Thus even if the larynx originally descended to exaggerate size, that says nothing about whether its current anatomical position was subsequently maintained, extended, or altered by selection pressures to enhance speech. The fact that Homo erectus had a spinal cord like that of other primates rules out an alternative hypothesis in which the change was an adaptation to bipedal locomotion.

The human larynx is permanently descended in women, children, and infants past the age of 3 months (Lieberman, 1984), all of whom speak or are learning to speak, and none of whom, in comparison with adult males engaged in intrasexual competition, had much evolutionary incentive to exaggerate size if doing so would incur costs in other functions.

This trait, as expected, is specifically found in males of reproductive age. Moreover, even with its descended larynx, the human supralaryngeal vocal tract is no longer than what would be expected for a primate of our size, because the human oral cavity has shortened in evolution owing to the fact that humans, unlike chimpanzees, lack snouts (Lieberman, 2003).

Finally, the descended larynx is part of a suite of vocal-tract modifications in human evolution, including changes in the shape of the tongue and jaw, that expand the space of discriminable speech sounds despite compromises in other organic functions, such as breathing, chewing, and swallowing (Lieberman, 1984, 2003).

In this they seem to me to be like a blind man, who, in order to fight on equal terms with a person that sees, should have made him descend to the bottom of an intensely dark cave: and I may say that such persons have an interest in my refraining from publishing the principles of the philosophy of which I make use; for, since these are of a kind the simplest and most evident, I should, by publishing them, do much the same as if I were to throw open the windows, and allow the light of day to enter the cave into which the combatants had descended.

In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species.

When we attempt to estimate the amount of structural difference between the domestic races of the same species, we are soon involved in doubt, from not knowing whether they have descended from one or several parent-species.

I do not believe, as we shall presently see, that all our dogs have descended from any one wild species; but, in the case of some other domestic races, there is presumptive, or even strong, evidence in favour of this view.

In the case of most of our anciently domesticated animals and plants, I do not think it is possible to come to any definite conclusion, whether they have descended from one or several species.