Question

Briefly give an evolutionary argument for human testes, our inability to make vitamin C, and our eyes. (NOTE: Not a description of each evolutionary development in the question)

Answer 1

The human testes - Arguably, the ugliest male part after male erectile organ, is the scrotal sac. This renders any argument based on its appearance, size, symmetry moot. Scientists earlier considered it to display the individual's genetic capability, just like a peacock's plumage. This viewpoint was thrown out simply because testicles weren't any more attractive than they were a million years ago. This indicated that it didn't have an exhibitionistic purpose. An evolutionary biologist came up with the "activation hypothesis". The human sperm develops at a temperature of 34-degree celsius. The descended scrotum allows quick dissipation of heat due to the thin layer of skin and since it's not embedded into the body it has a temperature of its own. During copulation, the scrotal sac is pulled upwards. The heat from the female reproductive organ, causes the sperms to become motile, this motility is important to ensure proper fertilization. The catch is that sperms can only survive at this higher temperature for a maximum of four hours and hence they need to be stored at a temperature lower than the body temperature.

Vitamin C -Primates rely on external sources of food. Apes and Chimps were primarily vegetarian. Fruits are high in vitamin C, and since early primates could get sufficient vitamin C from external sources, the body didn't need to produce it. The early humans lived on meat and berries. Berries are a good source of vitamin C hence the body doesn't need to produce it,

Human eye- Some scientists argue that the human eye is poorly designed as compared to the less evolved organisms. One striking difference is the presence of inverted retinas in the humans. It is intuitive to suggest that in order to capture the maximum light, and thus have greater sensitivity, the photoreceptors on the retina must directly face the light source. This non-inverted type of retina is seen in cephalopods.

Human vision is acute and very detailed. The human eye has a high processing power. The oxygen consumption of the retinoid tissue is 50% more than the kidney, 300% greater than the cerebral cortex of the brain and so on.

The assumption we make here is that the design in the cephalopods is much superior. Let's examine that assumption. Cephalopods can only detect patterns of movement. They only respond to patterns of movement, and if their prey is stationary, they won't be able to detect it, and thus won't attack. On the other hand, humans can detect the color, depth, texture, movement and everything else in the surroundings. I think the real problem here lies in our idea of what is a superior design and what isn't.