Why is the chemical nature of communication between organisms so ancient? To answer this question, one needs a bit of imagination and a wealth of scientific facts. Let us imagine our planet 3–4 billion years ago. At that time, it was shaken by powerful volcanoes, meteorite impacts, and intense tectonic activity. Gases escaped from huge fissures and craters on its surface and became part of its atmosphere. Since there was no ozone layer, the barren rocks were exposed to much stronger solar radiation than today. Any living being that happened to arrive on Earth back then would have been instantly killed by the intense radiation and the toxic primordial atmosphere. Radical changes had to occur on Earth before life could arise. And the presence of large bodies of water was essential. Water collected in low-lying areas, forming lakes, which in turn merged into seas and oceans. How many years it took for the world's oceans to fill is unknown. However, it is likely that the water level 2–3 billion years ago was roughly as high as it is today. With the formation of large bodies of water, the water cycle on Earth began. Water evaporated, saturated the atmosphere with water vapor, and returned to the oceans after condensation. The presence of water vapor in the atmosphere is an important factor for the emergence of life, as it, together with the ozone of the ozone layer, absorbs deadly ultraviolet rays.