In the fierce competition in the evolution of plants in order to protect themselves, they have evolved a variety of defensive measures to avoid herbivores grazed himself, especially its leaves. Some plants use acupuncture branches throughout the policy to allow the animals impossible under the and some plants on the leaves was poisoned, poisoned like to use my eating animals.
As omnivorous animal, human food plants also need to supplement the necessary vitamins and fiber. And food plants is a more safe and convenient food and clothing, to maintain their way of living. But some plants are poisonous, and some people just hate evolved trait toxic substances taste buds on the tongue of some plants contained, these people will feel the taste is very toxic substances "bitter" and does not like to eat, even if chewed too hard to swallow, so as to avoid poisoning.
Over time, people have these traits because it can avoid poisonous plants so as to obtain a strong survival advantage. In fact, avoidance of toxic substances is so important that human evolution of a series of genes encoding a total of 25 kinds of bitter taste receptors on the tongue taste buds, each receptor can make humans more than a dozen or dozens of substances on a category feel bitterness, all 25 species can feel the bitter taste receptors had thousands of bitter substances. Most of these substances are harmful to the human body or toxic substances, but of course there are useful though is bitter but then a small amount of human material.
In 1931, a named Arthur? Fox chemist accidentally Phenylthiocarbamide blown into the air, but except himself of many of my colleagues have complained about the kind of bitter substances. Later, after research scientists found that bitter taste and taste sensitivity trait is called propyl receptor genes. The bitterness taste gene called TAS2R38, No. 7 in the human chromosome.
There are two types of this gene, which are dominant and recessive genes G Gene C. One kind or propyl Phenylthiocarbamide G gene encoding human taste buds on the tongue's receptors. People will have this receptor in the presence of food and propyl similar compounds feel bitter taste. The C gene encoding the receptor does not taste the bitterness of this substance.
If a person with dual-dominant gene G, then he is very sensitive to bitter substances. If someone is a dominant gene G contains a recessive gene C, then he has a normal taste for bitterness. Others are carried by two recessive genes C, these people can not taste the bitterness of this very common vegetable substance. Bitterness is a taste aversion people are born, not taste bitter, and sometimes even feel that certain foods do not have a bitter taste, the proportion of people drinking this genotype will feel bitterness than normal to high.
An interesting thing is that for bitterness unconscious person would think 80% of tropical plants Antidesma feel bitter fruit unbearable. The feeling of bitterness normal person would think this fruit is sweet.
Feelings of bitterness, ability to avoid plants contain toxins is the ability of humans after a long natural selection was evolved. Chinese traditional medicine has a "bitter medicine" is that taste very bitter herbs on the human body is good on the table some of the bitter taste of food is also very popular. But in fact, most bitter thing is harmful to humans, such as some traditional "bitter medicine": realgar (arsenic-containing heat will break down as arsenic), mercury containing aloe, manshuriensis contain Aristolochia, can more or less cause harm to humans.
(Finishing from Science Park)
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