In August 2009, in order to measure this mutation rate, researchers turned their attention to the male-specific Y chromosome, because most of the DNA fragments are only passed down from father to son and do not fuse maternal genes. The changes are entirely due to nucleotide mutations.

This research was completed in collaboration with the Wellcome Trust Sanger Institute in the UK, the Chinese People's Liberation Army General Hospital, Shenzhen BGI Institute and other institutions.

Measurement results and DNA sequence analysis of the Y chromosome revealed that human genes accumulate 100 to 200 new mutations each time they are passed from one generation to the next.

This number is the first direct measurement of the mutation rate of a human gene - which equates to one mutation per 30 million base pairs.

Researchers from China and the UK analyzed tens of millions of base pairs on the Y chromosome of two distantly related men living in rural areas.

Their ancestors were the same person more than 200 years ago, so they inherited the same Y chromosome.

Over the next 13 generations, this Y chromosome was faithfully passed from father to son, although DNA copying errors occasionally occurred.

The researchers cultivated cells taken from the two people and used next-generation gene sequencing technology to discover 23 candidate mutations.

They then used traditional sequencing techniques to confirm 12 of the mutations. Eight of these mutations arose during the cell culture process, and only four were true genetic variations.

The researchers calculated that about one in 30 million base pairs is mutated.

The success of this direct measurement allowed people to accurately understand the pace at which humans themselves are evolving.