The problem is that if just one man, Homo Sapiens, lived before Adam then the whole Adamic sin and "ransome" sacrifice idea of the WT and others falls apart.
Men were building Temples and other structures 11,000 years ago and more.
Indeed, this is why I wrote this in a thread about Adam and Eve a few months ago:
It's amusing to imagine a naked Adam and Eve in 4000 BC, wandering around their Garden in wonder at everything, learning all kinds of new things as the "first humans", then looking over to the side as they stand near the edge of the property and noticing Mesopotamian workers walking by, dragging large stones to construct buildings in the center of their nearby city, Uruk. "Uh, hello?", they say, waving confusedly at their neighbors. God's voice booms from above, "Er, you should probably just ignore them."
"Uruk was an ancient city of Sumer and later Babylonia, situated east of the present bed of the Euphrates river, on the ancient dry former channel of the Euphrates River, some 30 km east of modern As-Samawah, Al-Muthanna, Iraq. [...] In addition to being one of the first cities, Uruk was the main force of urbanization during the Uruk period (4000–3200 BC). This period of 800 years saw a shift from small, agricultural villages to a larger urban center with a full-time bureaucracy, military, and stratified society." -- http://en.wikipedia.org/wiki/Uruk
"Ubaid culture is characterized by large village settlements, characterized by multi-roomed rectangular mud-brick houses and the appearance of the first temples of public architecture in Mesopotamia, with a growth of a two tier settlement hierarchy of centralized large sites of more than 10 hectares surrounded by smaller village sites of less than 1 hectare. [...] During the Ubaid Period [5000 B.C.– 4000 B.C.], the movement towards urbanization began." -- http://en.wikipedia.org/wiki/Ubaid_period