ThePouch
we did not come from a common ancestor. my first ancestors were Adam, Eve and Cain. ( Abel was murdered by his brother so i'm pretty sure he did not have any offsprings.)
Wait, you say we didn't come from a common ancestor, then said that we all came from Adam and his sons. Surely that would make Adam the common ancestor of all humans. And surely that would allow us to do some tests to find out when he lived.
See, there is a nifty trick you can pull off on DNA to find the last common male or female ancestor of any group of inderviduals. They have run tests on masses of the earths population.
By running genetic clocks backwards, we can calculate that the last common male ancestor of every man alive today lived about 60,000 to 90,000 years ago. Any more recently, it would be easy to spot.
Running a similar test on women gives you a date of about 150,000 years ago. So 'Eve' would have lived over 60,000 years before Adam. Makes sense, if you understand evolution. For creationists, this is a problem.
http://en.wikipedia.org/wiki/Mitochondrial_Eve
http://en.wikipedia.org/wiki/Y-chromosome_Adam