Secret signals of human sweat (Part 1)

If many women live together for a long time, their menstrual cycle will gradually become homogeneous. This is because pheromones in women's sweat are able to synchronize the menstrual cycle of people of the same sex.

Sweat secreted by humans also contains many mysteries.Photo: Corbis.com

Have you ever suddenly felt a sense of belonging and warmth when meeting someone for the first time? If you are a flyer, have you ever been afraid of flying? Those are fleeting feelings, but most of us cannot explain. After years of research, scientists have found answers to these seemingly irrational reactions of humans.

They are the reaction to the secret signals inside the sweat of others. Signals due to chemicals with a common name are pheromones. Pheromone is a relatively sensitive topic in biology. Although they exist in many living organisms, from insects to mammals, the number of human studies on pheromones can only be counted on the fingertips. So for a long time, we have only a vague understanding of human pheromones.

The situation has changed in recent years. Modern brain imaging techniques show that animal pheromones work not exactly the same way we think. Some scientists believe that humans can also produce and react with pheromones. According to them, it should not be questioned whether human pheromones exist, instead should start to understand how they affect human behavior.

Pheromone, first introduced in 1959, is the term for the chemicals that animals produce to stimulate instinctive behavior of the same type. For example, moths release pheromones to invite mates. When scientists find pheromones in animals, they realize their function is very diverse, not just to stimulate the instinctive behavior of the same species.

Since then the definition of pheromone has become a controversial topic. The most accepted definition follows: Pheromones are chemicals that function to transmit a signal that benefits both senders and receivers in terms of evolution.

No matter what definition we accept, the nature of pheromones does not change. They are an important part of the living world. Animals use pheromones to transmit information about themselves (such as gender and mating needs), physiological changes of other children (such as stimulating ovulation) and directly impacting behavior of the same type (warning about danger, inviting mating). Many mammals such as rats and deer often release pheromones to inform other animals in the herd of enemies.

For many years, it was thought that humans did not produce nor react with pheromones, in part because many scientists did not want to admit that humans also behave like animals. Another reason is that no one has found the mechanism of human brain response to pheromones.

Animals detect pheromones thanks to two tiny holes inside the nasal cavity. These two nostrils transfer the odor signal directly to the brain. Although humans possess an organ that functions like a pair of animal nostrils, we do not have nerve cells connecting it to the brain. We also have genes that regulate the activity of two extra nostrils, but they do not help the body produce receptor proteins capable of detecting pheromones. So many biologists think that humans have lost the ability to communicate with pheromones in a certain stage of evolution.

But this conclusion cannot prevent many scientists from continuing to study pheromones in humans. In 1971, Martha McClintock, a Harvard psychologist (USA), published a research result that shocked the public. According to her report, if many women live together for a long time, their menstrual cycle will gradually become the same. She said that pheromones in the sweat of women have the ability to synchronize the menstrual cycle of people of the same sex.

In 1998, Martha and a partner also discovered that women 's sweat during different periods of the menstrual cycle could reduce or prolong another woman' s menstrual cycle. Martha's conclusion became a controversial topic because no one had isolated the chemicals that caused the phenomenon.

Whether or not pheromones are involved in the search for partners in humans is also a controversial issue for many years. In the mid-90s of the last century, David Berliner and Luis Monti-Bloch - two faculty members of the University of Utah (USA), confirmed that when people smell the sex hormones of the opposite sex , our two side nostrils will emit an electrical pulse. In women, cells in this area responded strongly to extracts containing androstadienone - testosterone-derived derivatives of male sex hormones. Men also responded similarly to estratetraenol (found in female urine).

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