This week in New Scientist there is a rather odd question/answer:
I have just read Poor Little Warrior, a short story about a man who time travels to the dinosaur era, dies there and is fossilised. Can we be sure hominin fossils haven’t met a similar fate?
And part of one of the answers, from Richard Swifte, Germany:
More possible would be finding traces of people’s clothes, tools, ornaments or even buildings. Any hard non-organic objects could leave recognisable traces for a long time.
We can agree on the hard non-organic objects, to some extent (depending on what it is), but I hope this person is joking about the traces of people’s clothes. Textiles are notoriously difficult to preserve, and only survives in cases like Ötzi (due to freezing conditions, surviving ~5,300 years) and the mummies in the Tarim basin (due to dessication, surviving ~4,000 years). These are among the oldest pieces of clothing I can find references to: the Tarkhan dress was confirmed in 2016 as likely the world’s current oldest known woven garment, and it was dated to ~3366–3120 BC… so ~5,300 years old, perhaps.
How on earth does anyone reckon textiles could survive from 66 million years ago, the end of the dinosaurs? Much less from up to 245 million years ago? Some of our modern synthetic fabrics might leave some traces, but we haven’t done the long-term studies on that (for obvious reasons), and even then, fossilisation is a tricky business and most things do not ever fossilise.
More to the point, on the hominin question, we know that hominin fossils are not anatomically modern humans who have travelled back in time because they’re not anatomically modern; in cases where we have sequenced mtDNA (like the Denisovan remains), they are not mitochondrially modern; and they’re not isotopically modern either.
I’m not an expert on this, but I do know that we are what we eat, and I eat like a 21st century British human, so every bone has been made using the available building blocks — exposed to very specific levels of radiation. This is how we know that old remains like those of the Amesbury Archer (4,000 years old) come from places other than where they are buried: we know the Amesbury Archer was raised near the Alps, and definitely not in Britain, though he was found near Stonehenge.
And I cannot believe nobody explained this in response to the New Scientist question.