ABSTRACT
Diversity, made up of the number of taxa found in a dened area, is usually measured by counting species (species richness). In similar fashion, the diversity of genera or even families within a given area can be measured, and all of these are used as descriptors for what is called “the diversity of life.” Here I will describe another kind of diversity of life-not the number of species, but the number of separate chemistries of potentially viable life. It has been taken for granted, ever since Darwin said that it was so, that there is only one kind of life on Earth, even if it is subdivided into millions of species. That is our familiar DNA-life, which uses the same genetic code and same twenty amino acids to build the proteins for all species. Thus, if the diversity of life is based on a particular chemistry of life, it can be said that the diversity of life on Earth is one. A still unanswered question is whether Earth life is the only way, or but one way, to achieve a living status and, in reality, we do not know if DNA life is the unique chemistry of life on Earth. Thus, if there is other life in the cosmos (or even undiscovered here on Earth), how similar will it be to Earth life? All Earth life found to date is united in having DNA, a specic genetic code for the same twenty amino acids, and is water based. But is our life typical of all living cells throughout the universe, or just one way to construct a living cell?
