Born in Chicago, he received a bachelor of science in chemistry from Illinois Institute of Technology and his masters and doctorate in anthropology from University of California, Berkeley. He was a member of the Department of Anthropology at Stanford from 1967 to 1981, and taught at UC Berkeley from 1966 through 1994.
Along with his PhD supervisor Allan Wilson, Sarich measured the strength of immunological cross-reactions of blood serum albumin between pairs of creatures, including humans and African Apes (chimpanzees and gorillas). The strength of the reaction could be expressed numerically as an Immunological Distance, which was in turn proportional to the number of amino acid differences between homologous proteins in different species. By constructing a calibration curve of the ID of species' pairs with known divergence times in the fossil record, the data could be used as a "molecular clock" to estimate the times of divergence of pairs with poorer or unknown fossil records. In 1967, Sarich and Wilson published a seminal paper in "Science" that estimated the divergence time of humans and apes as 4 to 5 million years ago, at a time when standard interpretations of the fossil record gave this divergence as at least 10 to as much as 30 million years. Subsequent fossil discoveries, notably "Lucy", and reinterpretation of older fossil materials, notably Ramapithecus, showed the younger estimates to be correct and validated the albumin method. Application of the molecular clock principle revolutionized the study of molecular evolution.
Sarich's later work on race strengthened his reputation as a controversial figure. He applied his earlier work to racial differentiation, which he sees as the beginnings of speciation, arguing that the smaller the amount of time required to create a given number of morphological difference, the more selectively significant the differences become.
Sarich is a major proponent of sociobiology, evolutionary psychology, and the idea that racial differences represent the beginnings of speciation, which often caused him to be the subject of controversy by left-wing activists at Berkeley.
In 1994, Sarich was a signatory of a collective statement titled "Mainstream Science on Intelligence", written by Linda Gottfredson and published in the Wall Street Journal. Sarich also wrote a favorable review of The Bell Curve.
He currently lectures in anthropology at the University of Auckland, New Zealand.