Mitochondrial DNA has shown that a single woman existed on the African Savannah 150,000 years ago. The first male existed 90,000 years ago in the Rift Valley of Kenya.

I could get quite depressed.

I am relieved to find that, despite being a fairly sloppy piece of popular science jounalism, what the article actually said was -

Our mtDNA appears to coalesce in a single woman, who lived on the African savannah 150,000 years ago. Our Y-chromosome survives from a single man, who lived in the Rift Valley of Kenya or Tanzania 59,000 years ago.

This has been around for about 25 years and has been somewhat modified since. It is probably one of the most misunderstood ideas in popular science.

This Wikipedia article seems a bit out of date but gives the general idea - http://en.wikipedia.org/wiki/Mitochondrial_Eve

Bizarrely, this article from a creationist website seems to do its literature research very well before reaching some strange conclusions not supported by the evidence.http://www.trueorigin.org/mitochondrialeve01.asp