The statement of theory: {Evolution of organisms and biodiversity depends mainly on gene evolution through the appearance of novel genes. Biodiversity results from the DNA modifications induced by visible and non-visible environmental effects, the variation of gene expression, stresses, mutation, and invasion of genetic materials. Each individual belongs to the same species of living organisms has its own identity of DNA fingerprint}. The principles of theory:  Gene evolution depends mainly on gene duplication, a variety of environmental conditions, mutation, transposable elements, horizontal gene transfer (HGT). Also, de nove genes originated from non-coding DNA which mainly comes from retroviruses, exosome, micro-RNA, and invader nucleic acids from viruses, bacteria, or any parasite. Similarity and variations are the principles of life. In the same species, similarity produced from coding DNA while, individual variations arise from non-coding DNA. Aim and applications of theory:  The main prediction of this theory is not only each individual of human beings have his unique DNA fingerprint, but also any individual in the same species has also a unique identity in DNA fingerprint. Any living organism acquires genetic materials through their intimate contacts with other organisms and environmental DNA.  If the acquired genetic material reaches germ cells, it could transfer to the next generation giving new traits. Viruses considered the main source of genetic transformation in all living organisms. The genomic materials of some viruses could integrate inside the human genome like hepatitis B and HIV. The human genome has about 5 % viral genetic material, especially from retroviruses. This theory could explain the appearance of new individuals according to the transfer of genetic materials during intimate contact between different species and support many researchers who discovered new species.  Also, this theory may explain and will answer different questions; why husband and wife after some time, nearly acquire some similarities? Why people in the same geographical area nearly have a similar pattern? Why don't siblings match their DNA fingerprint? Also, it explains the host-parasite relationship depending upon the transfer of DNA and RNA in between.