Human remains from this period are rare and many have undoubtedly been destroyed by burial rituals or made useless by damage.[30][31] The most informative archaeological evidence are mummies, remains which have been preserved by either freezing or in peat bogs;[32][33] no evidence exists to suggest that prehistoric people mummified the dead for religious reasons, as Ancient Egyptians did. These bodies can provide scientists with subjects' (at the time of death): weight, illnesses, height, diet, age, and bone conditions,[34] which grant vital indications of how developed prehistoric medicine was.