A researcher team from the Northwestern University in the US have discovered that testosterone levels in a man drop after he becomes a father.
The study involved measuring the levels in 624 young men before and after their child was born.
As soon as the men became fathers, their testosterone levels dropped substantially, particularly in the month after the birth. Even larger falls in testosterone levels were seen when the man became more actively involved in the care of his offspring.
The male testosterone hormone has been shown to increase the male sex drive which is believed to aid in the competition for attracting a mate. Generally, a mans testosterone level does not change much, although it can change following a medical treatment and it does slowly decline as men age.
The researchers suggest that the drop in the testosterone levels help to make the man more family-orientated.
Christopher Kuzawa, an investigator in the study, suggests that the emotional, physical and psychological demands of fatherhood can lead to substantial changes in the male biology in order to cope. He said: “Raising human offspring is such an effort that it is co-operative by necessity, and our study shows that human fathers are biologically wired to help with the job.”
The researchers also suggest that the lower level of testosterone can also offer protection against certain diseases. Married men and fathers tend to have a better level of health than single men at a comparable age.