Thank you for this book. It sounded interesting, but I could not get into it. I will not post a negative review.

David Grinspoon, astrobiologist and Senior Scientist, Planetary Science Institute, is the author of two well-known books, Venus Revealed and Lonely Planets: The Natural Philosophy of Alien Life. His latest book that came out in 2016, Earth in Human Hands: Shaping Our Planet's Future offers some interesting thoughts. 

Milankovič cycles were first described by a Serbian geophysicist and astronomer Milutin Milanković in the 1920s. These periods are due to the eccentricity of the planetary orbit, the axial tilt, and the precession and they have a profound significance on how the earth evolved. The eccentricity causes 400,000 and 100,000-year cycles, the axial tilt 41,000-year cycles and the precession about 26,000-year cycles. These three cycles combine to affect the amount of solar heat that’s incident on the Earth’s surface and subsequently influence its climatic patterns.

The 26,000-year cycle (or 25,920 to be exact) could be perhaps one of the earliest cosmic mysteries cracked by human beings. Some believe that this was known to Mesopotamian and Indian civilisations in the Neolithic ages, around 5000 - 4000 B.C. It was estimated to be 25,920 years by the proto-scientists in the dawn of history, even before written languages were born. 

The sexagesimal, or base-60, the numeral system of the near-east arose because 25,920 is divisible by 60. Therefore 432, which is 25,920 divided by 60 is a sacred number for most ancient civilisations. This 'grand year' of 25,920 solar years was also responsible for the cyclic nature of time adopted all ancient religions in Mesopotamia, India and Egypt. One “Mahā-yuga” of Hindu calendar is 4.32 million years, and a “Kalpa" is a period of 4.32 billion years. 

Milankovitch cycles are now recognised significant to studies on palaeoclimatology and evolution of life. Appearance and demise of species are related to climatic events coinciding with these long cycles. It may have a role on how life first appeared on earth, how it became more and more complicated and ultimately to give rise to a particular species, the Homo Sapiens. Moreover, the Sapiens apparently have the ability to control these cycles if they decide to do so.

The idea of the lithosphere, hydrosphere, and the atmosphere was well understood for long. However, the idea that the controlling forces rise in the biosphere was the contribution of Vladimir Vernadsky, the Ukrainian geochemist. In his 1926 book, “The Biosphere”, he argued it was the life that shapes the earth. 

Vernadsky did not stop there. He talked about the “noösphere”, the sphere of human thought. He said that noösphere is the third in a succession of phases of development of the Earth, after the geosphere (inanimate matter) and the biosphere (biological life). Just as the emergence of life fundamentally transformed the geosphere, the development of human cognition fundamentally changes the biosphere. Going one step further, noösphere or another derivative arising from it may fundamentally change this planet or the cosmos itself. 

However, how did life on earth become such a formidable force? Where did it all this start?

Going by the whatever evidence we have, we are quite lonely. Gaia hypothesis, proposed in the 1970s by James Lovelock and Lynn Margulis, has steadily marched on to become Gaia theory or Gaia principle. Lovelock’s early career was in alien life exploration. He thought that life anywhere could be readily detected by the effects it makes, especially in the atmosphere. That later got him into Martian climate studies.

"Lynn Margulis’s name is as synonymous with symbiosis as Charles Darwin's is with evolution,” said historian Jan Sapp. She described the endosymbiosis theory that made complex life or eukaryotes possible. Eukaryotes, which includes humans like us, came into being after a bacteria made an archaeon its home. That bacteria continues to exist as mitochondria, the powerhouse of the cell, within all complex life. The chance encounter of a bacteria and an archaeon was also an incredibly rare event, having happened only once. Complex life is not easy to get. 

Gaia hypothesis prophesied that life in a planet cannot exist in niches. It has to be a planet-wide phenomenon. However, it has to start somewhere. Opinions on where this spot could be belong to the realm of speculation. The most favoured one used to be a warm pond somewhere on the surface of the earth, where lightning could strike. Warm pond hypothesis has started falling out of favour today.

Non-oxygenated early earth atmosphere had a surface bathed in ultra-violet radiations. No life can exist on a warm pond on the surface of the earth. If fact it was only very late in history, about 400 million years that life appeared on land. For the most of its existence, life hid in the deepest depths of oceans, where no light could penetrate. 

Plate tectonics is today evoked to explain all the geological process. Plate tectonics constantly keeps a planet a pulsating hub of constant movements. Volcanoes, earthquakes and tsunamis are all the effects of plate movements. Plate tectonics also gives rise to hydrothermal vents that rise from ocean floors. Discovery recently of alkaline hydrothermal vents like the “Lost City” changed our perception. 

In the early days of earth, in the absence of oxygen, alkaline vents are proposed to have acted as electrochemical flow reactors. Here alkaline fluids saturated in H2 mixed with relatively acidic ocean waters rich in CO2, through a labyrinth of interconnected micropores available in the deep-sea vents. The difference in pH across thin barriers of the vent walls produced natural proton gradients. The flow of electrons is electricity, the flow of proton, proticity. 

Life is nothing but proticity. The powerhouse of the cell, mitochondria, produces proticity.

Carbon fixation was possible thanks to proticity. Early single-celled organisms used their cell membranes to generate a proton flow that can produce hydrocarbon compounds. However, there is a limit to the amount of ‘skin’ one could have. This constraint disappeared when life invented mitochondria.

Another revolution that happened some time later was the appearance of cyanobacteria. Cyanobacteria were able to produce energy from sunlight. Photosynthesis was one of the first disasters to befall the earth. Oxygen, a deadly poison to most other life, was the waste product of photosynthesis. Most of life disappeared in this holocaust.

New oxygen tolerant forms slowly took over and reestablished life back on the desolate planet. Life is a tough bitch. The greening of the globe also started in a small way. For most of the land to become green, it took very long time more, after the oxygen in the atmosphere increased, and a protective ozone layer appeared. Ozone blocked the deadly ultra-violet radiations. Life surfaced from dark depths and hesitantly moved on to land. Land-based plants appeared in a big way only some four hundred million years ago.

Life has unintentionally changed the global physical environment. However, intentional shifts on a global scale belonged to a quite insignificant and weak species that came later. 
We know them as Homo Sapiens. However, they were only one among a score or more of human species that could walk and talk.

Human evolution has been pushed and pulled by the motions of the planets. Milankovič cycles saw the birth and death of species. They also heralded numerous ice ages of the past. The last glacial period started about 110,000 years ago and ended 12,000 years ago. 

Humans, including Homo Sapiens, retreated to caves when ice age started. When it ended 12,000 years back only one species remained - Homo Sapiens. All other cousins were long gone.
Surviving Sapiens emerged stronger and different. They stopped behaving like any other animal species. They started having beliefs and religions. They began having complex languages and philosophical debates. They started agriculture revolution, with which began the first intentional planetary-scale changes.

Sea level stabilised six to seven thousand years ago. The first large coastal settlements began emerging. Great civilisations developed in Iraq, Egypt and India. 
A new era, the age of humans, the Anthropocene emerged. It was a misnomer. No other human species, save the Sapiens remained by now. So it is not the Human era, but a Sapien era that was inaugurated.

The Sapien era saw how a single insignificant species could become the masters of a planet and start to decide how the physical environment and biosphere should behave. Ice ages came in tandem with Milankovič cycles in the past. Sapiens ingenuity made nuclear winter a possibility. 
The industrial revolution made intentional planetary change a reality. Sapien life induced global changes after the industrial revolution, though this became apparent only a bit later. Sapiens has already set foot on planetary bodies outside their home planet. 

From unintended damaging interventions, it is only a step away from intentional targeted planet-wide changes. We can call it the Terra Sapiens, the Wise Earth. 

Terra Sapiens is also only a step away from Cosmo Sapiens, the Wise Universe.