Researchers have discovered evidence of horse riding by studying the remains of human skeletons found in burial mounds called kurgans, which were between 4,500 and 5,000 years old. The earthen burial mounds belonged to the Yamnaya culture. The Yamnayans had migrated from the Pontic-Caspian steppes to find greener pastures in today´s countries of Romania and Bulgaria up to Hungary and Serbia.