Most men suddenly discover the loving and caring side of them when they become fathers. Researchers have found that there is a scientific reason to it.

According to the study done by the researchers of Northwestern University, a man's testosterone level falls at the time when his partner gives birth to a child, and a more caring and loving side of a man's personality comes into view as the level of hormones lowers down.

The study found that testosterone levels decreased by nearly one-third in the days and months after their partners gave birth. It showed that testosterone level dropped by 34 per cent on an average when they became fathers, with the biggest hormone drop in those males who were directly involved in childcare.

Testosterone is the key hormone that defines male physiology. A higher testosterone level in males is mostly associated with dominating nature, aggressive behavior, and strong sex drive.

According to the study published in the journal Proceedings of the National Academy of Sciences, the researchers followed 624 childless males in the Philippines in their early 20s and then after they became fathers. The researchers found that testosterone levels in males declined sharply when they became fathers.

 Raising human offspring is such an effort that it is cooperative by necessity, and our study shows that human fathers are biologically wired to help with the job, said Christopher Kuzawa, the co-author of the study.

According to The Telegraph report, Lee Gettler, an anthropology doctoral student who also worked with Kuzawa in the study, said: It's not the case that men with lower testosterone are simply more likely to become fathers. On the contrary, the men who started with high testosterone were more likely to become fathers, but once they did, their testosterone went down substantially, he said.

Lee explained that it was the act of childcare that seemed to reduce testosterone.