Did you know that your closest animal relative may not be the male-domiated, strength-regulated chimpanzee - it may very well be the female-led, sex-drenched bonobo. Male bonobos may have sex up to 3,000 times a day.
The control section of [voles'] DNA expands and contracts in the course of evolution so that members of a wild population of voles, the Emory researchers have found, will carry sections of many different lengths. Male voles with a long version of the control section are monogamous and devoted to their pups, whereas those with shorter versions are less so.
People have the same variability in their DNA, with a control section that comes in at least 17 lengths detected so far, Dr. Young said.
The control mechanism is also present in humans' two closest cousins, the chimpanzee and the bonobo, and bears on a controversy as to which of the two species humans more closely resemble.
Chimpanzees operate territorially based societies controlled by males who conduct often-lethal raids on neighboring groups. Bonobos, which look much like chimps, are governed by female hierarchies and facilitate almost every social interaction with copious sex.
The DNA sequence of humans, chimps and bonobos is generally very similar, but in the section that controls response to the hormone vasopressin, the Emory researchers have found the human and bonobo versions differ significantly from that of the chimp. Though not too much can be deduced from a single gene, the result shows that bonobos should be taken very seriously as a guide to human behavior and that the chimp is not the only model. - nytimes.com
So! Blame your congenital unfaithfulness on... well, it's congenital!