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"No fossil evidence has been discovered for ultramicroscopic intracellular replicators such as viruses." But didn't the genetic makeup of viruses suggest that they derive from the very earliest life forms? That virus-like creatures/entities were a middle stage between mere organic compounds and the first cellular beings? [probably not - since they are parasitic on cellular DNA they could not have arrived prior to their hosts. Books like the recent (2016)]A New History of Life have remarked this] I know there is no fossil evidence to back this up, and I'm not a biologist, but we might want to add that such things as viruses are thought to have been around throughout the Archean. Steinbach ( talk) 17:06, 17 January 2016 (UTC)
Red Planet X (Hercolubus) has been editing the start date for the Archean to be 3800 Mya, both in this article and in Template:Geological history. When I reverted, and asked for a reliable source, the editor provided a toolserver URL and reverted me. The current state of the article is now self-contradictory: it states both 4000 Mya and 3800 Mya.
Toolserver is not considered a reliable source (see WP:CIRC). There is a reliable source given in the article: the International Commision on Stratigraphy lists 4000 Mya as the start, as of 2013 [1]. Is there a better reliable source for 3800 Mya? — hike395 ( talk) 20:04, 12 January 2017 (UTC)
@ Triangulum: It's a nice-enough image for Earth's surface, but the Moon is depicted in a much later era. We see Aristarchus much as it appears today and Copernicus as a very young crater surrounded by fresh ejecta. We also see Procellarum, of course, as it predates Copernicus. I believe Copernicus has been dated as about 800 to 900 million years old and Procellarum at about a billion. Aristarchus, so bright because of its young age today, is considered approximately 450 million years old. In any case, Aristarchus is clearly a very young feature.
It may well be that the artist, rather than speculate on what may have occupied these parts of the lunar surface in Earth's Archean eon, played it safe by depicting the Moon with the features that we know about now. However, this means the Moon seen here is far more evolved than it was then. The near side would not yet have had all those maria.— BruceK10032 ( talk) 06:58, 28 April 2017 (UTC)
Apologies for the first part which was a mis-reading on my part. However, the last sentence of the lead states (or implies) that continents only formed during the Archean, but the main text says that some experts believe that the earth cooled enough to allow the formation of continents after 500 million years, thus in the late Hadean. Dudley Miles ( talk) 15:15, 15 April 2018 (UTC)
In the second paragraph on the geology of the eon, the following sentence is found: "Although a few mineral grains are known to be Hadean, the oldest rock formations exposed on the surface of the Earth are Archean or slightly older." Now, since any time "slightly older" than the Archaean is by definition part of the Hadean eon, this makes the sentence internally contradictory. I'm not sure what the author of the sentence intended. Should it be edited to remove the introductory clause about the mineral grains, or the final clause about "or slightly older"? Doug ( talk) 22:37, 16 April 2018 (UTC)
This article asserts that "(t)he earliest evidence for life on Earth is graphite of biogenic origin found in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland." I'm not an expert on the subject, but, to my knowledge, there is now evidence of even more ancient life, dating to 4.1 Ga during the early Hadean (as reported in Bell et al. 2015) [3]. The article should probably be updated to reflect this. Indianajoe13 ( talk) 17:52, 29 March 2022 (UTC)
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