Until now, the genomes of only two individuals -- James Watson, who co-determined DNA's double-helix structure, and maverick biotech entrepreneur Craig Venter -- have been unravelled.
Both men are of European descent, which leaves gaps in knowledge about how people of different ethnic backgrounds could be susceptible, or alternatively immune, to inherited diseases or respond to medicine.
Two studies, released on Wednesday by the British-based journal Nature, aim to fill in some of those blanks, with the genomes of a Han Chinese male and a man from the Yoruba ethnic group in West Africa.
The two teams describe the methods they used to expose the three billion base pairs of code in the anonymous individuals' DNA.
Later work, analysing the genomes of the four men, will compare and contrast changes in the code that could be linked to disease.
The two new genomes were compiled using sequencers made by Illumina Inc., a San Diego, California, biotech firm, which with rival firms 454 Life Sciences and Applied Biosystems has been credited with slashing the cost of genomics.
The first complete human genome was published in 2003, by the Human Genome Project, at an estimated cost of around 300 million dollars.
The sequence came from samples taken from several anonymous donors in Buffalo, New York, and is thus a composite of the human code for life rather than an individual picture.
In 2007, Venter's and Watson's genomes were unveiled within a short time of each other, at a reported cost of around a million dollars a piece.
Ultimately, biotech firms hope to sequence individual genetic codes for perhaps a couple of thousands of dollars.
Venter gave his own DNA as a sample for a race between the Human Genome Project and the firm of which he was president at the time, Celera Corp.
After being published as a draft in 2001, the genome was not completed in a polished version by Celera.
An international consortium called the 1,000 Genomes Project seeks to build the current library of four individual genomes to at least 1,000 people from around the world, in order to get the broadest possible view of the genetic mosaic.