Professor Graves’s prediction hinges around【根据】 the number of genes on the male and female sex chromosomes【染色体】. The female, or X, chromosome, contains a healthy 1,000 or so genes. What's more, girls and women have two of them. The Y chromosome started off with as many genes as its female counterpart. But over hundreds of millions of years it has crumbled away, leaving fewer than 100 genes in modern man. This includes the SRY gene, the ‘male master switch’ that determines whether an embryo is male or female.
However, there is some good news. She says that when Y chromosome falls to pieces, another chromosome could take on the role of the missing Y, leading to the creation of a new species of human.
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