What scientific evidence makes it obvious that humans were around earlier than (say) 8 thousand years ago?

Here’s a site that has a lot of articles on human evolution that you might use as a starting point: http://news.discovery.com/human/evolution

Human Why the question?

… and since you asked about the dating methods: http://en.wikipedia.org/wiki/Carbon_dating

Here is one article.

Here is annother.

http://www.pbs.org/wgbh/nova/evolution/becoming-human.html

The British Museum held an exhibition of ice age art recently

Barbara Bush & Nancy Reagan?

There are numerous ways of dating an object, C-14 (Carbon dating) being the most well-known, but others exist as C-14 is only reliable to about 40,000 years. This goes into more detail about radiometric dating.

As for what makes them credible, no science is ever credible to those who place faith above reason, as Galileo found out when he suggested that the Earth revolved around the Sun, so define “credible”. I’ve dealt with too many people who define it as, “How closely it aligns with my preconceived notions”, to avoid being a bit skeptical.

I think they found footprints that’s older than 8 000 years somewhere in Brittan. The Cradle of Humankind in South Africa comes to mind.

@jerv I have to admit, when I first saw this question I immediately thought https://www.youtube.com/watch?v=4F4qzPbcFiA&feature=kp

The Codes of Ur Nammu are older than 4000 years old.

Not only were there people, but the concept of perjury, slavery, and punishment for sexual assault were already litigated at that time.

Ötzi is somewhere over 5000 years old.
Lucy is over 3 million years old, but is a hominid rather than a “human”. If we assume that H. Sap. did not coexist with Australopithecus, that puts the earliest humans in between those two times. Of course, if they did coexist then humans are a lot older.

If you assume that all this stuff was made by humans, then note that some of it is more than 20,000 years old.

@rexacoracofalipitorius

The earliest known species of human, Homo habilis, first appear around 2.3 million years ago. We, Homo sapiens, first appear in the fossil around 200,000 years ago. We assume that H. sapiens did not coexist with Australopithecus afarensis because there’s no record of them ever existing anywhere near the same time frame.