How has the population grown from only two people?

In 2009, the US Census Bureau estimated that the world’s population was growing at the rate of 1.10% per year. At that rate, it would double every 63.3 years and the population would take only 2007 years to grow from 2 people to the current 6.8 billion. Obviously human beings have been around for a lot longer than that, and wars and epidemics have meant that the current population growth is higher than it has been at some times in the past (although it is a lot lower than it was 40 years ago). However, the calculation shows that there has been more than enough time for the entire population of the world to have come from Adam and Eve.

Reference:
http://www.census.gov/ipc/www/idb/worldpop.php