On Earth today, life is extremely diverse and, one might say, ubiquitous. Life exists everywhere: on land and in the sea, at a depth of several kilometers and in a shallow dirty puddle on asphalt, in the Arctic and Antarctica, in hot hot deserts and on mountain peaks, and even in volcanic craters. Living matter seems to envelop our planet in a continuous layer, and this layer is called the biosphere - from the Greek word bios - "life". But has it always been like this? Let's imagine that we have a time machine and take it on a trip to the Past. But first, let's get acquainted with the "route". The entire history of the Earth is divided into large - more precisely, huge - time intervals, which are called geological eras.We are living in the Holocene epoch of the Quaternary period of the Cenozoic era. So let's go?