ALMHOV, SWEDEN—Researchers studying cow teeth from southern Sweden dating to around 4000 B.C. have found evidence that early farmers there knew more about livestock husbandry than previously thought. By analyzing the oxygen isotopes in the teeth, the team found that cows were born over the course of a year, not just one season, indicating that the Neolithic farmers could control when calves were born. “It’s very interesting that the farmers of the period were able to manipulate the calving seasons, so all the calves did not come in the spring,” Durham University's Kurt Gron told ScienceNordic. “This is very hard to do, and would not have taken place if the farmers had not intended to do it.” By controlling the calving season, the farmers had access to milk year round, which suggests to some archaeologists that the farmers were so sophisticated that they were probably immigrants from central Europe where such livestock practices were already established. To read about the technology used by people around this time in Europe, go to "Neolithic Toolkit."