Gravity and Biology

Gravity has been the most constant environmental factor throughout the evolution of biological species on Earth. Organisms are rarely exposed to other gravity levels, either increased or decreased, for prolonged periods. Thus, evolution in a constant 1G field has historically prevented us from appreciating the potential biological consequences of a multi-G universe. To answer the question 'Can terrestrial life be sustained and thrive beyond our planet?' we need to understand the importance of gravity on living systems, and we need to develop a multi-G, rather than a 1G, mentality. The science of gravitational biology took a giant step with the advent of the space program, which provided the first opportunity to examine living organisms in gravity environments lower than could be sustained on Earth. Previously, virtually nothing was known about the effects of extremely low gravity on living organisms, and most of the initial expectations were proven wrong. All species that have flown in space survive in microgravity, although no higher organism has ever completed a life cycle in space. It has been found, however, that many systems change, transiently or permanently, as a result of prolonged exposure to microgravity.