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Hypotheses : Humans could not have appeared on the earth earlier than 3.75 billion years ago.

Proof :

1 Potassium 40 is the radioactive emission from the human body that relatively has the largest half-life. (1.25 billion years).

2 The age of the Solar System is 5 billion years old.

From 1 And 2

For a human with a stable configuration [longest half-life determinable] -

humans could not have existed on Earth for more than 3.75 billion years.

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On 3/13/2021 at 1:23 PM, HallsofIvy said:

Less than 3.75 billion years?  Well, Okay.  Most scientists put the first Homo Sapiens on earth at about 30 thousand years ago. That's a lot less than 3.75 billion!

But it did not start with Home Sapiens.  Life started about + 3.75 billion years ago with simple life forms, like bacteria, evolving into more complex living organisms, evolving into early hominids,  ancestors to all apes, which in time evolved into great apes (hominids) and finally into Homo Sapiens.

All species of modern apes have a common hominid ancestor which appeared about 5-7 million years ago:

When Humans Became Human

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On the biggest steps in early human evolution scientists are in agreement. The first human ancestors appeared between five million and seven million years ago, probably when some apelike creatures in Africa began to walk habitually on two legs.

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They were flaking crude stone tools by 2.5 million years ago. Then some of them spread from Africa into Asia and Europe after two million years ago.

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With somewhat less certainty, most scientists think that people who look like us -- anatomically modern Homo sapiens -- evolved by at least 130,000 years ago from ancestors who had remained in Africa. Their brain had reached today's size. They, too, moved out of Africa and eventually replaced nonmodern human species, notably the Neanderthals in Europe and parts of Asia, and Homo erectus, typified by Java Man and Peking Man fossils in the Far East.

https://www.nytimes.com/2002/02/26/science/when-humans-became-human.html#

Early Humans, Neanderthals, Denisovans Mixed It Up

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As a more recently-discovered group, we have far less information on Denisovans than Neanderthals. But archaeologists have found evidence that they lived and mated with Neanderthals in a Siberian love shack for around 100,000 years. The most direct evidence of this is the recent discovery of a 13-year-old girl who lived in that cave about 90,000 years ago. DNA analysis revealed that her mother was a Neanderthal and her father was a Denisovan.

Human Evolution

https://www.history.com/news/humans-evolution-neanderthals-denisovans

Edited by write4u
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