How long have humans been on earth?

Scientifically, no one knows. Christians, citing from Genesis, say Adam was the first human and he lived to be 930.

I'm Armenian, I like this Story, Armenia is also the earliest Cristian Nation, And Had the First Christian Church, Don't know the accuracy of the following:
Armenian Highlands: the birth place of civilization -------------------------------------------------------------------------------- I hope the following information will interest you. Based on my exposure to European and Near-Eastern research regarding genetics, archeology, mythology and linguistics, I have come to the conclusion that the aboriginal homeland of Armenians and all proto-Indo European and Aryan tribes were somewhere within the vicinity of the Armenian Highlands (eastern Anatolia, northern Mesopotamia, north eastern Iran and the southern Caucasus), more specifically, within the triangle formed by the Caspian sea, the Black Sea and the Mediterranean Sea. Putting aside wishful thinking and fairytales propagated by self-serving "Euro-centric" White Supremists on the one hand and equally unreliable Zionist saturated academia within America and England on the other hand, there is a large body of evidence that mainstream western academia has not been exposed to yet that clearly points to the Armenian Highlands as the primordial location where civilized man as represented by Indo-European and Mesopotamian tribes first entered the pages of history. According to Armenian and some European scholars and scientists, the following statements are either accepted as corroborated facts yet to be disproved by other discoveries elsewhere, or very likely speculation and/or theories that yet need to be corroborated through additional research. Thus, based on the evaluation of various scholarly and scientific disciplines, the Armenian Highlands are said to be: The earliest location where metal smelting is said to have taken place. The earliest location where agriculture is said to have been developed. The earliest location where animal husbandry is said to have been developed. The earliest location where wheeled transportation is said to have been implimented. The earliest location where petroglyphs of wheels, ox carts and swastikas are depicted. The earliest location where mankind is said to have developed a keen understanding of movements of the stars and the planets. The earliest location where cyclopic walls and round dwelling have been unearthed. The earliest location where some of the Babylonian, Sumerian, Iranian, Celtic, Slavic, Germanic and Greco-Roman gods and goddesses have their primordial predecessors. The location where Babylonian/Sumerian and Hebrew sacred texts indicate the civilization/mankind was first "created." The location where Babylonian/Sumerian and Hebrew sacred texts indicate the world was repopulated after the Great Flood. The location where, according to Hebrew sacred scripture, God is said to have changed the languages of mankind, thus, scattering them to the far corners of the world. (in my opinion, most probably a metaphor describing the Indo-European language diffusion) The following web-sites are related to the aforementioned statements: Indo-European homeland, Armenian prehistoric artifacts: http://www.armenianhighland.com/home...onicle120.html Karahunge: Armenia's "stonehenge" advent of astronomy: Armenia's Stonehenge Shengavit: a seven thousand year old dwelling: http://www.armenianow.com/2003/nove...atures/history/ Metsamor: Pre-ancient dwelling a center for metallurgy and astronomy: http://www.tacentral.com/history/metsamor.asp / http://www.tacentral.com/astronomy.asp Petroglyphs: Neolithic depictions of celestial bodies, swastikas, wheeled transportation, etc: http://www.arminco.com/hayknet/naskal.htm / Armenian Rock Arts Pre-historic religions within the Armenian Highlands, Armenian national gods and goddesses: HaYaSeR / My Home Page

Current theory is that the first "recognizably human" Home Sapiens emerged in Africa about 400,000 years ago. Prior to that there were earlier homonids that appear to have been "cousing" to Homo Sapiens (not necesarily direct ancestors) , including Homo erectus and Homo Neanderthalis. The earliest known species of the genus Homo is Homno habilis, which lived in Africa about 2.4 Million years ago.

There is no known "first" individual human being, just as there is no known "first" individual cat, or T. Rex, or apple tree.

See: Human evolution - Wikipedia, the free encyclopedia

The first human beings on earth were Adam and Eve created by God. God does not say when it happened only that it happened on the 6th day. A day to God is like a thousand days and a thousand days is like a day meaning God does not operate with time as humans do. He is not limited by time or space. Man may think they know but they can only speculate. Anything to bring contradiction to Gods Word.

What you say is true, but the receptive did ask for a scientific explanation.

I thought I would expand on Jeremiah333 answer
Modern man is called Homo sapiens and has been around for about 250,000. However the Homo genus is perhaps two million years old.

Which of our ancestors would you call a human being?
We have several close relative in the human family. Our close relatives are termed Homo. This is the genus that includes modern humans and our close relatives such as Neanderthal Man (Homo neanderthalensis) and Flores Man (Homo floresiensis).

Both of these groups lived outside of Africa before our ancestors left Africa (perhaps 80,000 to 100,000 years ago). And both survived until fairly recently. Neanderthal man survived in western Europe until perhaps 30,000 years ago. Flores Man survived until perhaps 15,000 years ago on the Indonesian island of Flores.

For more info look at Human evolution - Wikipedia, the free encyclopedia

Since we are the product of continuous evolutionary process it is difficult to say at what point the first human being lived.

@jeremiah333... Anything to bring contradiction to science.