Sunday, February 12, 2012

Oestrogen makes males attractive to other males

Chemicals produced by cells to induce behavioural changes to other cells are often called hormones. They travel to the blood in order to eventually find their target: a receptor somewhere on the cell's surface. A class of chemicals similar to hormones travels in a slight different way: they are excreted by the organism, instead of dumped into the blood. They make their way to an other organism of the same species, where it induces behavioural changes. These molecules are called pheromones, and they are thought to play an important role in the mating process, possibly even in humans. Scientists from Oregon State University have shown that oestrogen, which is actually a known hormone, can influence pheromone levels in snakes: males that excrete it in high levels attract other males, which are interested in mating. In a previous study scientists showed that male-female attraction is also governed by DNA.

According to the scientists, the oestrogen excreted by the snakes they investigated is the same as found in other animals. Humans use it as female sex hormones, which may explain why, when acting on the production of pheromone in snakes, attracts other males. Apparently, they do not care that the mate they are attracted to is actually a male, and not female. It seems that the 'message' sent by oestrogen is strong enough to overcome physical differences.

Scientists from Oregon State University studied red-sided garter snakes in their natural habitat, but added a little oestrogen to some of the test subjects. They found that when males possess higher levels of the hormone, larger amounts of pheromone are produced as well. In turn, it caused sexual interest in other male snakes: they preferred male snakes that produced high levels of pheromone over females. To further illustrate that oestrogen production results to male attraction, they measured levels of the hormone in females. What they found is a correlation between the attractiveness of a female and the level of oestrogen production.
Chemical message
Cells need to send messages to each other because they need to cooperate. Trillions of individual messages are sent throughout your body every second every second. We humans send messages to each other by speech, but are also affected by other signals such as body language and smell. Chemical messages work in pretty much the same way as speech: one individual, being a cell or a whole organism, produces it, and another individual receives it. For each type of chemical message there is a specific receptor on the cellular surface. They 'capture' the message, and induce changes inside the cell, which eventually lead to changes in gene expression and thus cellular behaviour. In a nutshell, that's what happens in biological communication, albeit on a large scale. When it comes to red-sided garter snakes, chemical messaging has profound consequences. The snakes use pheromones to assess species, sex, population, season, reproductive condition, size and age. Basically, the chemicals tell them all that needs to be known of a possible partner.

Males and females are naturally attracted to each other. Evolution has favoured sexual reproduction over a-sexual, the latter being cells dividing themselves, for example. There are several things that make males attractive to females, and vice versa. Obviously, looks play an important role, but scientists take more and more interest in the actions of pheromones, hormones that act between organisms, instead of inside them. Snakes have shown to send extremely strong messages and signals packaged in pheromones. We think humans are also, albeit unconsciously, affected by pheromones. However, there is still some controversy about the extent in which we are influenced by these chemicals.  

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