Thursday, May 3, 2012

The Rift Valley and Evolution


NASA Image, Rift Valley
It's incredible to think about all of the natural forces that came together to create a sentient species on this little blue planet of ours.  There are so many interesting ways to approach the question of our origins. The Great Rift Valley in Africa is a place that elicits such conversations.

What can  geology, the study of rocks and the physical earth, tell us about human origins, for example?  The crust is constantly on the move due to the internal heat of the earth’s interior. Along the Pacific rim, the sea floor is forced back into the depths of the earth forming a vast ring of volcanic fire;  In India, the Himalayas rise as the plates crush into each other.  How can any of this relate to human evolution?

In East Africa the land is being literally ripped apart by the same great forces.  A new ocean will soon sever the continent apart and the horn of Africa will become its own separate land. The African Rift Valley also happens to be the place where our first human ancestors evolved. Could there be a connection between the colossal forces working within the earth and the evolution of life and of human kind?

NASA Map of Rift Valley
Life has blossomed on earth due to the geologically active earth’s interior.  It is the reason why our planet has a magnetic field. Without that field life would be in deep trouble as it protects the earth from the sun’s periodic ejections of radioactive particles. The magnetic field also keeps the atmosphere from being slowly ripped away by the solar wind. Just look at poor Mars as an example of planet that has cooled and lost its shield.

But as far as the human story of evolution, the influence of geology may go further than that. Evolution is all about adaptability. Over the course of about five or six million years the development of hominids may have been spurred by the geomorphic changes happening across the African Rift Valley landscape. As its geology changed, bodies of water formed and disappeared, the climate became cyclically wetter and drier, and in turn the surrounding ecology adapted.

Every creature has evolved in its own unique ways. Nature is amazingly creative in that regard. Perhaps, changes in the Rift Valley favored hominids that were cleverer, more able to survive by using intellect, in turn, encouraging early humans to develop larger brains, and leading ultimately to us.

There were also global climatic changes during this time, possibly related to plate tectonics, as well as changes in the relationship of the earth and sun. Earth has experienced a few dozen ice ages in the last few million years, each one radically changing life on the planet. All but one hominid species went extinct. Climate change is no hand maiden.

In any case, a particular combination of species, land forms and climate change in the Great Rift Valley is probably why you are reading this right now.

Now that’s something to think about. There seems to be a lot that goes into making sentient life, and it seems to be a fragile process. Perhaps it is quite rare in the universe, but I doubt we are the only example, as we now know there are likely tens of billions of planets just in our galaxy alone.