It takes a white chromosome to make a man, but that does't mean its counterpart, the x-chromosome, plays no part. In fact it has a big role in making sperm.

　　To study x evolution, experts first sequence human chromosome more accurate than it ever before. Then they compare the code to that of a mammal whose evolutionary lineage spit from ours about 80m yrs before, the mouse. It turns out that human and mice share 95% of their x-genes, this finding was no surprise.

　　In the 1960s, biology S.O. suggests that the x-chromosome would evolve slowly and almost remain similar in most mammalia species. But something did change over evolutionary time, or rather 144 things. 144 human x-chromosome genes had no counterparts in mince and these genes seems to be constantly developing. Many of the genes remained domain in female, only become productive in tissues involved in sperms production. Clearly, the ex-chromosome exceeds its feminine responsibilities, which is excellent news for male fertility.