If the man in your life has gorilla-like tendencies, this could be why.

Scientists have discovered a strong similarity between the human and gorilla Y chromosome.

Both have more in common with each other than they do with the same male-specific chromosome in the chimpanzee, our closest animal cousin.

The discovery was made by scientists who compared the DNA sequence of the Y chromosome in all three species.

Lead researcher Professor Kateryna Makova, from Pennsylvania State University in the US, said: "Surprisingly, we found that in many ways the gorilla Y chromosome is more similar to the human Y chromosome than either is to the chimpanzee Y chromosome.

"In regions of the chromosome where we can align all three species, the sequence similarity fits with what we know about the evolutionary relationships among the species - humans are more closely related to chimpanzees.

"However, the chimpanzee Y chromosome appears to have undergone more changes in the number of genes and contains a different amount of repetitive elements compared to the human or gorilla. Moreover, a greater proportion of the gorilla Y sequences can be aligned to the human than to the chimpanzee Y chromosome."

The Y chromosome of mammals is difficult to sequence for a number of reasons. One is that males only have a single copy of the chromosome, paired with a female X chromosome. Females have two X chromosomes.

Another problem that has to be overcome is the unusually high number of repeated DNA sequences in the Y chromosome.

Prof Makova's team used a combination of new techniques to gain better access to the Y chromosome's genetic information.

In future, it could be used to study male infertility disorders and aid the conservation of endangered species, said the scientists.

The findings are reported in the journal Genome Research.