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What is the oldest fossil ever found on Earth? Where and when was it found? What was the oldest fossil with a brain with 2 hemispheres ever found?

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    $\begingroup$ The question is nice but brain is maybe confusing. Does a flatworm with a little central nevious system has brain? then the question will be quite close to say what is the ancient metazoo fossil found, were I believe you were trying to ask secondly for the first cordata with well developed brain maybe. btw you won't find the nervious system if it is a fossil $\endgroup$ – Universal_learner Aug 7 '18 at 8:02
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    $\begingroup$ And once you get into micro-fossils and chemical fossils, then there's a lot of debate and disagreement. Eg. Carbon isotope anomalies around 4Ga have been interpreted as being possibly due to life, but that is controversial. There is generally wide agreement that we have micro-fossils by 3Ga. Varying amounts of disagreement cover micro-fossils in the 4Ga-3Ga range... $\endgroup$ – winwaed Aug 7 '18 at 14:29
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    $\begingroup$ You have asked two questions Muze. For oldest fossil they will talk you about what @winwaed talks you. It is more chemical evidences of life than fossils. With brain? Well that's a quite strange question. A neurologist should then answer firstly what's a brain, and then remember a fossil has not organs, so the answer could become realy tricky to answer. I think it would be more clear if you tell the first cordata, or the first metazoo/pluricelular -geologist are very interested in Cambrian Life Explosion, the Ediacaran Phaune and so.... $\endgroup$ – Universal_learner Aug 8 '18 at 1:03
  • $\begingroup$ @winwaed sounds like start to a great answer! $\endgroup$ – Muze the good Troll. Aug 8 '18 at 4:20
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The oldest undisputed fossil are Stromatolites, bacterial mats, the oldest of which are dated ay 3.7 billion years ago. The key term here is undisputed, there are other possible fossils but it is very hard to have certainty with chemical or cellular fossils. The oldest uncertain fossils trace back to 4.28 billion years and are possible bacteria trapped in hydrothermal vent products.

The oldest fossil of a creature with a brain is weird. it is actually several creatures from Ediacaran biota. These are also some of the oldest multicellular life fossils, lacking any hard parts fossilization of early small animals is incredibly rare event even considering how rare fossilization already is. There are several bilaterally symmetrical animals capable of movement, this combined with the fact they are more than two cells thick means they almost certainly had a brain.

Kimberella and Spriggina and their relatives are both almost certainly mobile, with some form of nervous system based on phylogenetic bracketing, others are also likely since the ancestor of chordates may in there somewhere. We know there were moving creatures from the ediacara because we actually have trace fossils that are consistent with a muscular moving organism like anemone.

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