The history of harvest festivals goes back to ancient times. Almost all ancient people, from slaves to emperors, depended on the harvest for food. They, unlike modern humans, did not have reserves to fall back on in the event that the harvest failed. As a result, they felt they needed to trust their gods to give them a good harvest. They would often pray to the gods before a harvest and throw a religious festival afterward. They would feast with their friends and family and give part of the harvest to the gods as a measure of thanks. Over time these celebrations evolved into holidays. Halloween was originally a pagan harvest festival that Christianity adopted (along with Christmas). Thanksgiving originated as a harvest festival that the pilgrims created to celebrate surviving and not starving during their first winter in America. Even if the harvest is not as important today, many harvest festivals have evolved into a series of popular holidays that many people commonly celebrate.