As we have learned throughout the year, natural selection occurs when environmental pressures give selective advantages to certain mutations in a population, which give individuals greater chances to survive and reproduce. Plants are preyed on by a variety of herbivores and omnivores, and as a result plants who secrete poisons to avoid being eaten have been selected for. Since people from thousands of years ago were omnivores, they may have been killed by eating some of these plants. So, a variation on humans, which Dr. Moalem calls supertasting on page 84, was selected for. Plants' poisons taste bitter to a person's palate, and the supertasters can sense this easier, which helps them avoid eating poisonous plants. But, as Dr. Moalem says on page 85, foods like broccoli, which taste bitter, may help humans survive, as broccoli may help defend against cancer.
Relating to Big Idea 1, are supertasters still being selected for? Against? Are there still selection pressures on tasting ability in today's society at all? Did the poisonous plants drive the evolution of peoples sense of taste? Did the humans eating plants drive the plants evolution? Or was it co-evolution? On page 85, Dr. Moalem states that broccoli has compounds that can help fight cancer. Is it possible to get these compounds from something besides broccoli so that supertasting is still a selective advantage?
Zachary Rane (zrane3@students.d125.org)
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ReplyDeleteToday we are so heavily reliant on others to obtain or create the necessary food that we eat, that our skills and adaptations in discerning what's healthy and what's not has become flawed. This is because all it takes for us to be nourished is to go on down to the local grocery store or McDonalds and choose what satisfies our appetites. Therefore, the need for supertasters nowadays is diminishing. Not only is the accessibility of food a large component of not needing supertasters, but there are also other ways, such as lab testing, to make sure certain plants don't have any chemicals in them that can harm us.
ReplyDeleteThere are three groups of tasters researchers refer to. There are non-tasters, medium tasters and supertasters. Research has concluded that about 25% of the population are supertasters, 25% are non-tasters, and 50% are medium tasters. This shows stabilizing selection where the intermediate phenotype, medium tasters, is favored and the extremes, non-tasters and supertasters, are not as favorable, yet the extremes are able to survive due to the vast selection of foods we have available today. In today’s society supertasting has been found to be unfavorable. As mentioned, broccoli contains a compound that can help prevent the growth and spread of cancer. Therefore, supertasters are at a disadvantage and theoretically have a higher chance of getting cancer because they avoid foods that prevent it. The good news is that other foods can also provide this compound, glucoraphanin. Broccoli is in a group of vegetables called cruciferous vegetables which all contain glucoraphanin. Vegetables in this group also include cauliflower, brussel sprouts, cabbage, and bok choy. So there are other ways of obtaining this cancer preventing chemical. On the other hand, supertasters can also be selected for because they tend to shy away from foods high in fats, salt, or sugar, thus making them more healthy. This helps them avoid many current conditions such as obesity, hypertension, and even heart disease. Therefore, it is difficult to say whether or not supertasters are selected for because the circumstances we face today are much different than when our bitter taste receptors were selected for about 100,000 to 1,000,000 years ago (Moalem 84).
I believe that as natural selection took its course, co-evolution took place in order to select for the plants that were able to avoid being consumed, and the consumers that were also able to avoid this plant. This relates to Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties. Since the plant also provided as a food source for many other organisms such as animals and insects, this adaptation must have been enabled to ward off these predators. As many of the predators that attempted to eat this plant died, it signaled humans that this plant must be dangerous. This led us to believe that if one bitter tasting plant was poisonous then all bitter tasting plants were poisonous. So, those able to detect bitterness to decide which plants were to be avoided and which were to be eaten were selected for.
References: http://www.bbc.co.uk/science/humanbody/body/articles/senses/supertaster.shtml, http://www.webmd.com/food-recipes/features/super-veggies-cruciferous-vegetables
(Ted Nowak, tnowak4@students.d125.org)