It’s been said that if a machine ever gains awareness, it will be not due to our careful programming, but to an unforeseeable anomaly. Perhaps the first anomaly occurred back in the distant primordial fog of human evolution. We may never know. But a new analysis of ancient genomes suggests that different branches of the human family tree interbred multiple times, and that some humans carry DNA from an archaic, unknown ancestor.
“The oldest traces of life are fossils of marine microbes dating back almost 3.5 billion years. It was in the oceans that multicellular organisms evolved; their oldest fossils date back to about 2 billion years ago,” observes Carl Zimmer in Planet of Viruses. “Microbes may be invisible to the naked eye,” he adds,”but collectively they dwarf all the ocean’s whales, its coral reefs, and all other forms of marine life.”
“Our moon is a witness to the history of the solar system,” says planetary scientist Kentaro Terada at Osaka University in Japan, referring to the lack of erosion on moon’s surface and evidence from the Copernicus crater and glass impact spherules from Apollo landing sites of a massive asteroid storm about 800 million years ago, in which two quadrillion kilograms of rock rained down the moon and Earth. A cosmic storm of about 30 and 60 times as much mass as the Chicxulub impactor that ended the reign the dinosaurs– kickstarting the most brutal ice ages in the planet’s history known as the Cryogenian epoch.
Science fiction writers have long had bizarre, vivid images of extraterrestrial life from Plutonians resembling intelligent ice cubes to H. G. Wells’ vision of silicon-aluminum men in “Another Basis for Life” dwelling in an atmosphere of gaseous sulfur on the shores of a liquid iron sea. Astrobiologists have hotly debated how closely extraterrestrial life would evolve to resemble that on Earth, with some arguing that with a slightly different roll of the “Darwinian dice”, Earth would have been inhabited by creatures unimaginable. Others argue that if there is biology elsewhere in the universe we would find it strikingly familiar down to the carbon-based machinery in its cells.
From about two million years ago until around 10,000 years ago, the world was inhabited, at one and the same time, by several human species, one of the earliest being Homo erectus, who walked upright and were built like modern humans, and they eventually spread from Africa, across Europe and Asia. Our possible direct ancestor, Homo erectus, researchers have discovered, crafted a cutting-edge tool out of a hippo’s leg bone around 1.4 million years ago in the early Acheulean, starting our immense journey from ax to algorithms and perhaps Homo sapiens last great invention, artificial intelligence.
Has life started many times of Earth? Could life as we know it today on our pale blue dot in fact be a second genesis? Could Earth’s original microbial life have formed four billion years ago, only to be destroyed some ten million years later during the age of Late Heavy Bombardment by massive asteroids sterilizing the planet? But perhaps some of this primordial “life as we don’t it” survived the 200-million-year barrage of huge objects followed by a second genesis of microbial life representing our form of life co-existing to this day with a “shadow biosphere” of Earth’s original alien life forms.
