There is a hypothesis that a̳l̳i̳e̳n̳ beings must have a biological structure similar to the human species.
Nevertheless, there is an opinion that the life of a̳l̳i̳e̳n̳s can be radically different from that of humans. This was told by SETI Senior Astronomer Seth Shostak, who is looking for e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ c̳i̳v̳i̳l̳i̳z̳a̳t̳i̳o̳n̳s̳ and signs of their existence.
Seth believes that due to a misconception about the life of e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ beings, humanity cannot find reliable traces and information about their presence. The scientist’s guess is based on the age of the Earth.
The Earth is a relatively young planet compared to the cosmic bodies in the Universe. For this reason, humanity can lag several times behind in the development of technology.
A̳l̳i̳e̳n̳s can live outside of biological existence for a long time. As an example, Seth cites the development of artificial intelligence that allows their species to function outside the biological world.
The astronomer said that in the search for e̳x̳t̳r̳a̳t̳e̳r̳r̳e̳s̳t̳r̳i̳a̳l̳ c̳i̳v̳i̳l̳i̳z̳a̳t̳i̳o̳n̳s̳, one should aim at signals from technosignatures, the study of chemical compounds, radio emission and light.