Define 'spirit of life': It is impossible to succeed in defining 'spirit of life' as people 4500 years ago understood it. We might approximate it by studying the concept as it is understood by modern traditionalist indigenous people, in tandem with pertinent information gathered from other ancient and prehistoric cultures. However, based on my studies I would say that there is a good chance people of Salisbury Plain ca. 2500 BC knew life to be a result of an infusion of an immaterial spirit from the cosmos into a material body derived from Earth. Matter alone is not, cannot live without a force derived from some unknown location. The Lakota call this force Wakan Tanka - Great Mystery, Mysterious Power. Expression of this power is found in movement of air, wind. Motion is an indicator of life. All things move. It is this power that causes animals to breathe. Its source is somewhere within the Winter Hexagon.
Note that my definition of 'spirit of life' is of no consequence here. I work hard to avoid including my personal beliefs in my writings when I discuss beliefs and intentions of ancient and prehistoric cultures, although I admit it is impossible to not include personal preference, perspective and bias in my work. After all, that is something that separates each writer form all other writers. My interest is not in comparing my beliefs with ancient and indigenous people, but to discover what those people were thinking and communicating to us via the symbols they left behind. I believe those symbols are key to recognizing, identifying and understanding the achievements of prehistoric humankind. Stonehenge is an excellent example of such achievement!