First-born girls tend to engage in sexual activity in a later age than their younger sisters, a new Australian research has revealed.The study, discussed at an Australian Society for Human Biology conference on Wednesday, also points out that the reproductive behaviour of children are affected by the order in which they are born into a family.While a previous study has revealed the difference in the behaviour and family-orientation of the children, the new study notes the difference in their reproductive strategies, including the age at first sexual intercourse, first pregnancy and first birth with the middle-born children standing out in the survey results.While Middle-born males have sex for the first time at a younger age than their brothers, last-born females are younger when they have sex for the first time, the report pointed out, according to 'Courier Mail’.But middle-born children of both sexes tend to have fewer children of their own, the report suggests with females 2.6 times more likely to fall pregnant at any given age.Researcher Fritha Milne of Western Australian University, said her work confirmed that the first five year of a child's life are crucial."During this time the young must elicit support and resources from the parents," she said adding "If there are any siblings, then they have to compete for the limited resources of the parents. Claiming her research to be "really interesting," Milne said "it gives you some insight into people's behaviour and allows you to see that the behaviours displayed by later-born children could be just an adaptation to their place in the world."
