LIFE & EXTINCTION –EVENTS ON OUR PLANET – WHAT WE KNOW 

The evolution of life on Earth has been gradual, spanning glacial epochs, or ice ages, and interglacial epochs like the Holocene, the name of our present 11,700 year long interglacial period. In addition, a number of randomly distributed planetary scale disruptive events have caused mass extinctions and restructuring of the biosphere. While the Industrial Revolution clearly marked the beginning of a period of unparalleled creativity, technological development and growth in human populations, the associated demand for land and consumption of fossil fuels has also brought rising global temperatures, habitat destruction, pollution, and ongoing mass extinction of plant and animal species that threaten to transform current ecosystems and food webs, and potentially to overwhelm their capacity to mitigate extreme events and disturbances. It has also emerged that the Total Fertility Index for the developed world – the measure of whether a population is growing or shrinking – is now well below the steady state value of 2.1 children per woman capable of bearing children, with typical values now around 1.6. By contrast, for sub-Saharan Africa this number is around 4.

Placed within this context, we may consider that while our telescopes have begun to detect occasional extra-solar planets that may be capable of supporting life, they have seen no indication of the kind of broad heat signature we might expect from any expansive human-like advanced technological civilization. One interpretation would be that precursor civilizations tend to fail at some key obstacle on the path to sustainable outward expansion.