The report presented by the University of California San Francisco (UCSF) describes the other X chromosome women have in relation to men, the possible cause of female life and other physiological benefits.
The human Y chromosome has few brain genes and is not necessary to survive, the study said.
Based on experiments with mice, researchers analyzed the effects of female mammals of having two X chromosomes, compared to men who have only one and the other Y.
In contrast to the biological wealth given by the female X chromosome, only the masculine Y "contains a few genes different from those that create secondary sexual properties like male genitals and facial hair and are not necessary for survival," the publication says. .
"We have long been thinking about what causes female life expectancy," says researcher Dena Dubal, professor of neurology at UCSF and leading author of the study, published today in the scientific journal Aging Cell.
"We can imagine that nature has led women to develop in this way, and when you live longer you can make sure your offspring have welfare and possibly their descendants," Dubal said.
The researchers compared laboratory mice with four different combinations of chromosomes and gonads (organ-forming male or female gametes), the two found in nature -XX in the ovaries and XY in testicles – and two others created in the laboratory.
When manipulating a gene, combinations came from XX chromosomes implanted into testicles and XY chromosomes in the ovaries.
"The mice were genetically identical, except for their sex chromosomes, but everything else, including the environment, was the same," said the study.
The longest life was achieved in the mice with XX chromosomes in their ovaries, which exceeded the average life of 21 months and also reached 30 months.
The XX genes implanted in gonads prevented the early death of the animals, but they only extended their lives in one or two months.
"For a longer lifetime, mice must have ovaries with two XX chromosomes, according to the natural order," Summarized Iryna Lobach, Assistant Professor of Epidemiology and Biostatistics at UCSF and co-author of the report.