Question

It can be inferred from the passage that human populations vary considerably in their:

• A. Sensitivity to certain bodily odors
• B. Ability to assimilate artificial chemicals
• C. Vulnerability to certain toxins found in plants
• D. Ability to discern bitterness in taste
• A. PTC is not a naturally occurring chemical but rather has been produced only recently by scientists.
• B. Most humans lack sufficient taste sensitivity to discriminate between PTC and bitter chemicals occurring naturally.
• C. Variability among humans respecting PTC discrimination, like variability respecting earwax, cannot be explained in terms of evolutionary adaptivity.
• D. Unlike non-human primates, humans can discriminate intellectually between toxic and non-toxic bitter substances.
• A. Artificially synthesized chemicals might eventually serve to alter the course of evolution by desensitizing humans to certain tastes and odors.
• B. Some human polymorphisms might be explained as vestigial evidence of evolutionary adaptations that still serve vital purposes in other primates.
• C. Sensitivity to taste and to odors have been subject to far greater natural selectivity during the evolution of primates than previously thought.
• D. Polymorphism among human populations varies considerably from region to region throughout the world.
• A. The amount of bodily odors and secretion that take place reduce at each stage of evolution.
• B. The extent of attention paid by non-human primates to body secretions is much higher than that of the more evolved human species.
• C. Artificially synthesized chemicals have impaired the extent of sensitivity that human beings have to body secretions.
• D. All of these

Answer 1

The Correct Option is D

The passage mentions the significant variation in the percentage of people who can taste the artificially synthesized chemical phenylthiocarbonide (PTC) across different human populations. It suggests that this variation is related to the ability to discern bitterness in taste, which has evolved over time as a means to discriminate toxic substances. Therefore, the most reasonable inference is that human populations vary in their ability to discern bitterness in taste.

Answer 2

The passage explains that PTC is an artificially synthesized chemical, and the evolutionary history of humans has not acted directly on it. Since PTC is not naturally occurring in the environment, it would not have been subject to the same evolutionary pressures as naturally occurring bitter substances that humans needed to discriminate for survival. This suggests that evolutionary history did not act on PTC specifically.

Answer 3

The passage suggests that human polymorphisms, such as the ability to taste PTC and the variability in earwax, may be vestigial traits—evolutionary remnants of traits that served important functions in the past, like distinguishing toxic plants or responding to body odors, which are still relevant in non-human primates. This fits best with the idea of evolutionary adaptations that may have had vital purposes in the past.

Answer 4

The passage refers to the attention that non-human primates and humans pay to bodily secretions, specifically in relation to cerumen (earwax) and other odorous bodily fluids. It suggests that non-human primates pay more attention to these body secretions, which might have played a role in evolutionary selection, while the human focus on these traits has diminished. This reflects the idea that non-human primates pay greater attention to body secretions than humans do.