User talk:217.7.192.169

Hi, Thanks for the page. There is sth. unclear but:

Under Terminology it says:

After about 2.5 billion years, oxygen generated by photosynthesizing single-celled organisms began to appear in the atmosphere marking the beginning of the Proterozoic....

Question: 2.5 billion years after what event??? After the formation of the earth(?), would mean: 2 billion years ago, which is not the beginning of the Proterozoic (2,5 billion years ago).

The emergence of „earliest oxygen“ in the atmosphere is listed on the same page as 1 billion years after the formation of the earth or 3,5 billion years ago.

To make the Proterozoic fit in any way, the sentence above could be changed to „2,5 billion years ago“, rather then „after 2,5 billion years....“. Still the emergence of oxygen does won‘t fit into the sentence.

Thanks Stephan Heberger