Q: If human beings were wiped out by some sort of catastrophe such as a lethal virus, meteorite impact or the effects of global warming, would any evidence of our existence and intelligence remain to be discovered by an intelligent life form inhabiting the Earth 65 million years later?
A: One indication of intelligent life that may survive 65 million years is the close association of metal objects with human remains. People have gold/ mercury fillings, wear jewellery and have surgical implants, all of which remain with them after death.
In the distant future, humans will form a significant part of the fossil record due to the culture of burial, which increases the chances of preservation. Intrinsically related to these future fossils will be the metal artefacts that we carry with us. The highly resistant nature of jewellery metal (gold and platinum) and surgical steels will mean that in many cases corrosion from groundwater and sediment diagenesis will be minimal.
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If the delicate remains of sea creatures can survive in the fossil record, so can the metal objects associated with modern humans, which, of course, reflect the intelligence required for metallurgy.
A: Nearly everything that humans construct is metastable and will revert to simpler chemical forms over time. There is a degree of decay even in the highly stable materials used for the Egyptian pyramids and the statues on Easter Island, yet these are very young in geological terms. None of our steel, concrete, glass or plastics will last even a million years.
If anything survives us, it will be partially modified superstable materials. Conceivably some advanced ceramics might resist weathering buried deep in the soil, but would they be recognisable?
Of course, one thing will remain as an indelible record of our intelligence, and that is the extinctions that we are causing. Even 65 million years from now, the fossil record will show that the diversity of large animals on Earth fell rapidly around this time. The record of the smaller animals and plants will also show that a major extinction event occurred around now. An intelligent species 65 million years in the future will find it puzzling that the megafauna survived the series of recent ice ages, and then died out in unison all over the world in this particular interglacial period.
Perhaps they will associate the extinctions with a worldwide pulse of erosion and the laying down of thin layers of fine clays across the ocean beds of the Earth. But will they recognise this as the work of an intelligent species? I think not.
A: Assuming the next intelligent life form has achieved space travel, it may well find some junk on the Moon relatively unchanged, including a plaque reading 鈥淲e came in peace for all Mankind鈥� signed by one Richard M. Nixon. Wbether they would be correct in interpreting this as an artefact of intelligent life is a moot point.
A: After 65 million years the world as we know it would scarcely exist. The continental surface upon which we live is the most unlikely place for our remains to be preserved. Scavenging, weathering, glaciation and tectonic processes will surely remove our traces. Fossilisation requires very rapid removal from the effects of oxygen and the simultaneous mineralisation of the remains, and both are improbable.
Buildings and human remains may be preserved if they are entombed rapidly in volcanic ash on a subsiding coastal plain 鈥� Japan for example 鈥� as in the Roman towns of Pompeii and Herculaneum. Humans may be preserved if they are entombed in a swamp such as the Everglades or the Mississippi Delta. Tectonic uplift of these areas might expose the rock strata for geologists of the future.
Perhaps geologists will also find evidence in these rocks of unusually high quantities of industrial pollutants, in the form of metals such as lead, zinc, mercury and cadmium. This may echo the widespread iridium anomaly which is supposed to mark the impact of a large meteorite leading to the demise of the dinosaurs.
There is also a possibility that those same tectonic processes will have exposed our underground nuclear waste repositories, leading to great puzzlement at the unusual mechanism which enriched certain isotopes of uranium. Plutonium and other unnatural elements and isotopes will have quietly decayed away by then.