And it's not just oil. It's all the minerals we've been mining since the dawn of civilization - take copper: before copper age one could find nuggets of pure copper metal [1], in ancient Egypt it was produced from ores with 10-12% copper [2]. 21st century copper ore has an average of 0.6% copper in it [3]. I doubt that ancient Egyptians could have done much anything with 0.6% ores.

[1] http://en.wikipedia.org/wiki/Metallurgy_during_the_Copper_Ag...

[2] http://www.reshafim.org.il/ad/egypt/timelines/topics/mining....

[3] http://en.wikipedia.org/wiki/Copper_extraction_techniques