See also tree of life

Tree of life

The concept of a tree of life, a many-branched tree illustrating the idea that all life on earth is related, has been used in science , religion, philosophy, mythology, and other areas...

 for other meanings of the term.

The Tree-of-Life is a fictional plant (the ancestor of yams

Yam (vegetable)

Yam is the common name for some species in the genus Dioscorea . These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania...

, with similar appearance and taste) in Larry Niven

Larry Niven

Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...

's Known Space

Known Space

Known Space is the fictional setting of some dozen science fiction novels and several collections of short stories written by author Larry Niven. It has also in part been used as a shared universe in the Man-Kzin Wars spin-off anthologies sub-series....

 universe, for which all Hominid

Hominidae

The Hominidae or include them .), as the term is used here, form a taxonomic family, including four extant genera: chimpanzees , gorillas , humans , and orangutans ....

s have a built-in genetic craving. Consumption of Tree-of-Life makes human-related species turn into Protector

Pak Protector

Pak Breeders and Pak Protectors are two forms of fictional life in Larry Niven's Known Space universe. The Pak first appeared in "The Adults," which appeared in Galaxy in 1967; this story was expanded into the novel Protector by Larry Niven...

s, as a result of a symbiotic

Symbiosis

Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

 that grows in the root; however, the virus requires enough thallium

Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...

to develop, which is why it failed to grow on Earth. To those too young to develop into Protectors, Tree of Life smells repugnant, while the virus is fatal to those too old.