Trace the evolutionary history and adaptive significance of each of the followin

Question

Trace the evolutionary history and adaptive significance of each of the following human adaptive complexes deep adaptations, (adaptative complexes that we modern humans have inherited from our deep evolutionary past). In other words, develop an illustrated/illuminated handwritten account that traces the evolutionary history of each complex across deep time. Human Hearing System (focus on the evolution of the mammalian hearing system) Human Vision System (stereoscopic, retinal fovea, trichromatic color vision) The Human Hand (with long, strong opposable thumb, short fingers, nails backing tactile pads with dermatoglyphs, precision and power grip, etc.)

Explanation / Answer

These primitive fish have organs of balance. These fish have embedded under their skin, along the length of its head and body, a series of depressions or grooves known as the 'lateral-line'. Groups of hair cells just beneath the grooves detect differences in water pressure, which allows the fish to adjust to variations in currents and eddies.

These grooves evolved into the structure of the inner ear found in all vertebrates, including humans. The nerve cells in the inner ear are adaptations of earlier hair cells sensitive to the motions of liquid. The middle ear and the Eustachian tube evolved from the respiratory apparatus of the fish, while various inner ear structures were developed from parts of the fish jaw. In mammals, the quadrate and articular bones (of reptiles) have evolved into the incus and malleus bones in the middle ear.

The cochlea is the auditory portion of the inner ear. It originated in the late 17th century. Within the mammalian cochlea exists the organ of Corti, which contains hair cells that are responsible for translating the vibrations. The size of the basal turn of the cochlea was not different in Neanderthals and Holocene humans, however it became larger in early modern humans and Upper Paleolithic humans. Furthermore, the position and orientation of the cochlea was similar between Neanderthals and Holocene humans, relative to plane of the lateral canal, whereas early modern and upper Paleolithic humans have a more superiorly placed cochlea than Holocene humans. Modern humans have long cochleae, but the space devoted to each frequency range is quite large (2.5mm per octave), resulting in a comparatively reduced upper frequency limit.

The vision of all vertebrates can be classified as diurnal or nocturnal. For nocturnal vision, retinae rich in rods, which are more sensitive to dim light than cones is a necessity. Diurnal vision requires numerous cones, which give clarity of images with focusing in good light, so the retina foveae of diurnal vertebrates are pure cone. The human fovea is pure cone, but outside the macula, rods outnumber the cones by 20 to 1.

The evolution in placement of eye played major role in human stereoscopic vison. Humans have two eyes located side-by-side in the front of their heads. The close side-by-side positioning, each eye takes a view of the same area from a slightly different angle. The combined image is more than the sum of its parts. It is a three-dimensional stereo picture.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.