27 March 2018

The key adaptation

For some time now, I've been fond of pointing out to people the view that the evolution of human intelligence, with its capacity to transfer technology culturally rather than only as biological adaptation, is very probably the most important development in the history of life on Earth at least since the evolution of photosynthesis, about 2 billion years ago. Another contender, actually even more fundamental from the point of view of the evolution of complex organisms, especially animals, would be the evolution of Eukaryotic cells, which resulted from the chance merger into what's called endosymbiosis of two bacterialike precursors (actually a bacteria and an archeon). This chance event required not only that two cells merge and one not have eaten the other but both continue to live in one envelope, but that they reproduce together and continue as one organism with diverse ancestry... a very unlikely event, which almost certainly only happened once. Virtually all macroscopic life is descended from that first eukaryote. 

From Daniel Dennett's From Bacteria to Bach and Back, here's an illustration of the point, which he credits to the polymath Paul MacCready (of Gossamer Albatross fame). MacCready calculated that at the dawn of what's sometimes nowadays referred to as the Axial Age, i.e., the invention of agriculture, about 10,000 years ago, humans and their dependent pets and livestock consisted of roughly 0.1% of the land vertebrate biomass of the Earth. Today, after 10,000 years of cultural evolution, the figure is 98% (mostly cattle). No doubt Homo sapiens is part of "nature," but there can be no doubt that our species has changed the biosphere of this planet more than any other single species ever, and we're just getting started. When the time comes when terrestrial life is found on thousands of planets across this section of the Galaxy, which will happen unless we commit species suicide, it will be safe to say that this thing we think of as intelligence is the key adaptation for the long term survival and expansion of life in the universe. 


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