In 1911, an Anthropologist by the name of Theodora Kroeber discovered the last living member of the Yahi Tribe in Northern California. She took him with her to her home in San Francisco, and introduced him to modern life. Through working with him, teaching him her culture she slowly learned to communicate with him. By communicating with him she learned as much as she could about his culture, and his way of living, and by doing this, she was able to write a book about him and his extinct tribe. Through this book she interpreted that spirits were a big part of life for the Yahi Tribe. They asked the spirits for help when they needed it, and talked to the spirits for advice, the spirits even existed in their dreams. Spirits were one of the many reasons they believed that they were so close to nature. The spirits existed in every living and non-living living creature and object. .
When the Yahi People were alive they understood that all living and non-living creatures had a spirit, whether it was good or bad. Ishi realized that if he spoke with the spirits and asked them to take the bad away, that they would try their best to do so. This theory is well explained in the following quote: .
"May the roots of the manzanita catch your feet and throw you.
May the thorns of the thorns of the chaparral tear your clothes and hold you.
May the poison oak snap against your faces so you do not see where you step.".
In this quote Ishi is praying that the Saldu will not see his animal trap, because if they see the animal trap they will discover Ishi's tribe and kill the remaining seven Yahi people in the tribe. .
In this book Ishi also discusses his friend, Timawi's death. When Ishi explains Timawis death to his Uncle he says, "his spirit is released. He lies with the Ancestors. I have bathed and said the purification prayer." This is an important quote because it explains how the Yahi's looked to the spirits after death.