Charles Darwin in his On the Origin of Species discussed the difficulty of believing that natural selection can explain the development of the variety and perfection of complex organs like eyes in the animal kingdom. The PAX6 gene found in animals from zooplankton to humans regulates eye formation and explains mutants.
Our speaker will be Robert Yee, MD. Bob is the Merrill Grayson Prof of Ophthalmology & Chair Department of Ophthalmology - Emeritus, IU School of Medicine.
Robert Yee: Photo: Carl Holl
Today’s Presentation
Program: Darwin's Dilemma: Evolution of Eyes.
Speaker: Robert Yee, MD, Merrill Grayson Professor Emeritus of Ophthalmology and former Dept. Chair, IU School of Medicine, Scientech Club member
Introduced By: Andy Ratermann
Attendance: NESC: 90, Zoom: 29
Guest(s): Linda Yee and one more unrecorded.
Scribe: Russell Judd
Editor: Carl Warner
View a recording of today’s Zoom presentation at:
Today's program 061724
Our talk today was given by Dr. Robert Yee, the Merrill Grayson Professor of Ophthalmology and Chairman of Ophthalmology Emeritus at the IU School of Medicine. Bob is a member of our Scientech Club. His talk was about Darwin’s book on evolution and natural selection, but he didn't believe that the theory explained the development of the eye. There are two types of eyes: the camera type and compound eyes. Camera type eyes are found in mammals, birds, and fish. Compound type eyes are found in many insects such as bees, dragon flies, and fruit flies. Compound eyes have units of pigmented photoreceptor cells and each unit creates a small image and when combined, a complete image.
Vision is complex and acuity needs vary with creature types. To suppose that the eyes’ mechanisms for distance adjustments, different amounts of light and color could have been formed by natural selection does not seem correct. But if gradations from a simple and imperfect eye and a complex eye can be shown to exist, and if the eye does vary so slightly and the variation be inherited, and if every variation be useful, then the difficulty of believing that a complex and perfect eye could be formed by natural selection could be overcome.
Darwin’s solution is a prototype eye consisting of a neural cell and a pigmented cell covered by a membrane without a lens. It would detect light and its direction. A more perfect eye would evolve by mutation and natural selection.
Recently genes called PAX genes have been discovered on chromosome 11p13’s distal region. These genes (about 150) control embryo body design and produce factors that control cell functions and brain and spinal cord development. The PAX6 gene helps with the formation of eyes and olfactory bulb. In vertebrates, it is the master regulator of eye development. Defects in these genes can result in aniridia glaucoma or problems with the cornea, the lens, or nystagmus (a vision condition in which the eyes make repetitive uncontrolled movements).
Thank you Dr. Yee, for giving us recent information about gene discovery, eye development and Charles Darwin.
