She was thinking that for thousands of years, when people died – especially powerful people, especially people who were feared – the survivors had gone to a lot of trouble. They’d slit the throats of their best horses, they’d buried slaves and favourite wives alive, they’d poured blood into the earth. It hadn’t been mourning, it had been appeasement. They’d wanted to show their good will, however spurious, because they’d known the spirit of the dead one would be envious of them for still being alive.
Robber Bride – Margaret Atwood
The burial of horses and goods and wives was an old tradition practiced most fervently by the pharaos in Egypt but the Chinese had similar traditions too:
A 2,400-year-old pit containing the remains of horses and chariots believed to belong to a member of an ancient royal household has been uncovered in China.
The Russians did it too:
Warrior king found in ancient Russian tomb: Scythian ruler was buried with riches, weapons and even his HORSE
I believe that even from ancient times, people were dedicated to the afterlife. This was perhaps because their mortal lives were relatively short; very few lived to beyond 40 years old. Mummifying their dead was a way to preserve and prepare them for the afterlife (mummies have been found from Egypt all the way to Peru and Siberia). Items that might be useful in the afterlife were also customarily buried with the dead including everyday objects, foods, beverages, jewelry, pets and servants. The people believed that life after death was similar to life on Earth, so they felt it was important to include all the daily necessities in their burial tombs. If items were not in the tomb, the dead would not have access to them in the afterlife. Some kings began filling their tombs long before their deaths to ensure they would have all they needed and wanted.
Most Mesopotamians (Sumerians) were buried in cemeteries. The bodies were laid on their backs in individual graves. The graves were sometimes reopened to place a second family member instead. Why did they do this? Who was generally the second family member? Maybe they placed the wife or husband with the first body. Alas, we do not have this information.
Some of the graves contained the bodies of dogs. It was common for pets to be buried just like their owners, with the same care that is. Meat bones have been found placed near the mouths of dogs to be food for the afterlife.
As time moved on, the people sacrificed were replaced with statues or symbolic items. This practice has continued until today when people are buried holding on a precious item (to them).