Sensitivity to environmental vibration, of which our sense of hearing is a specialized example, is found in unicellular organisms as well. The external ear and associated internal specializations developed in mammals, although convergent specialization of skull bones for hearing occurs in other terrestrial vertebrates. Certain fish have an entirely different specialization for "hearing" in which a sensitive structure is associated with the swim bladder, detecting faint vibrations. Thus, most of the structure of mammalian ears is indeed a relatively late innovation, compared with the use of nostrils in smelling (at least present in fish), the vertebrate eye (in conodonts), etc. Proprioception, however, seems to have undergone substantial improvement at roughly the same time. This is the internal sense of body motion, i.e., why you can close your eyes and still tell where your hands are as you move them without touching something for reference. The fossil evidence on pro!
prioception is non-existant, so estimates of its timing depends on the condition of modern animals. External ears have a dismal fossil record, but the internal specializations involve bone and so do a bit better.
Dr. David Campbell
46860 Hilton Dr #1113
Lexington Park MD 20653 USA
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droigate Spa
---------- Original Message ----------------------------------
From: "D. F. Siemens, Jr." <firstname.lastname@example.org>
Date: Sun, 21 Oct 2001 19:45:48 -0700
>Keith gives a good answer from one viewpoint. But we may carry matters
>further back if we think of basic sensitivity to various types of
>stimuli. Touch is found in the sensitivity of bacteria to attachment, and
>also in the repulsion reflex of paramecia, for example. I recall that
>_Balantidium coli_ does not bounce off on contact, and so bores through
>the intestines of its hosts. Vision can probably be ascribed to the red
>spot of Euglena and certainly to the eye spots of helminths. But the
>algae and blue-green bacteria seem to have a more rudimentary ability to
>orient relative to light. However, the formation of images probably is
>first found in arthropods' compound eyes. I can't separate taste from
>smell at the most basic level of chemical sensitivity. It is evident in
>bacteria as well as fungi and protozoa. The earliest sensitivity to
>vibration that comes to mind is the earthworm. The earliest production of
>sounds for signalling is probably among arthropods. As Keith notes, just
>what does Jeans mean?
>On Sun, 21 Oct 2001 17:03:10 -0400 george murphy <email@example.com>
> On skimming Sir James Jeans' Science & Music (first published in
>1937) I noted the closing sentence:
> "Students of evolution in the animal world tell us that the ear
>was the last of the sense organs to arrive; it is beyond question the
>most intricate and the most wonderful."
> Is the statement in the first clause now correct? If so, it
>suggests an interesting theological reflection.
>George L. Murphy
>"The Science-Theology Interface"
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