Sex-biased investment in children has been explored in a historic population in northern England, 1600 to 1800, following a family reconstitution study. An examination of the wills and other available data identified three social groups: the elite, tradesmen, and subsistence farmers. The community lived under marginal conditions with poor and fluctuating levels of nutrition; infant and child mortalities were high. Clear differences were found between the social groups, and it is suggested that the elite wetnursed their daughters whereas the elite (...) mother breast-fed her sons for only a short period and introduced supplementary feeding early. The wives of the tradesmen probably breast-fed both sexes for the same length of time. Subsistence farmers may have weaned their sons earlier than daughters. The results are discussed in terms of possible differences in investment strategies. The investment strategy of the elite group was probably male-biased but may, in practice, have favored the female offspring. (shrink)