The Y sex chromosome of men will not become extinct, according to a study published on Wednesday in the journal Nature. Researchers compared the chromosomes of humans to a Rhesus monkey, a species that separated from human ancestors 25 million years ago, and to chimpanzees, which separated 6 million years ago. The data show that the genetic decay in the Y chromosome was quick at first, but then became minimal in recent history - there is no further gene lost within the past 6 million yeard. \"The Y is not going anywhere and gene loss has probably come to a halt. The genes (in Y chromosome) that remain on it have critical biological functions, and that means they are going to survive,\" said Jennifer Hughes from the Whitehead Institute in Cambridge, Massachusetts, the United States. \"We can\'t rule out the possibility it could happen another time, but the genes which are left on the Y are here to stay,\" she added. The finding challenged the previous researches which suggested the Y chromosome may become extinct in five million years\' time, based on the rate at which genes are disappearing from the chromosome.