Why is the sense of smell of dogs and monkeys so sharp and efficient compared to human senses? Scientists from the Weizmann Institute of Science and the Max Planck Institute in Germany offer an answer to this age-old mystery
Trained dogs are able to identify, through the sense of smell, the escape route of suspects, or the reality of drugs, or explosives. Why are humans unable to do this? Why is the sense of smell of dogs and monkeys so sharp and efficient compared to human senses? Scientists from the Weizmann Institute of Science and the Max Planck Institute in Germany offer an answer to this age-old mystery.
In all mammals, including humans, there are about 1,000 genes that encode unique protein receptors located in the nasal mucosa and whose role is to bind molecules of odorants, and in this way identify different smells. But not all of these genes work properly, and in fact, the percentage of defective genes determines the sharpness of the animal's or human's sense of smell.
In previous studies carried out by Prof. Doron Lantz's group from the Department of Molecular Genetics at the Weizmann Institute of Science, it became clear that in humans, more than half of the genes encoding receptors have become pseudo-genes, that is, genes that include a mutation expressed in a sort of "stop" command that prevents the gene from functioning properly. But an open question remains: is this a relatively ancient phenomenon, which also applies to various monkeys, or does this genetic "disaster" apply only to the human race. To answer this question, the scientists compared the DNA sequence of a sample of 50 genes encoding olfactory receptors in humans and different species of monkeys. Thus it was discovered that while the percentage of defective genes in chimpanzees, gorillas, orangutans and rhesus monkeys was only 28 to 36%, the percentage of defective genes in humans reached 54%.
This study also allowed for an accurate reconstruction of the destruction process, showing that it occurred very quickly, in the evolutionary "blink of an eye": only three to five million years. From this comes the conclusion that the reduction in the sharpness and efficiency of the sense of smell is the property of humans only, and it probably stems from the development of the brain in "human" directions such as emphasizing the importance of sight, developing the ability to distinguish between colors as well as the ability to recognize other details based on facial features and not based on smell.
The research team included Yoav Gilad, a research student at the Feinberg Seminary of the Weizmann Institute of Science, who conducts part of his research at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Prof. Doron Lantz, the supervisor at the Weizmann Institute of Science, Orna Man, another research student in Prof. Lantz's research group, and Prof. ' Svante Paabo, head of the research institute in Germany. The research findings were recently published in the scientific journal "Records of the American Academy of Sciences" - PNAS.
