Evolution
The early evolution of the Hepatitis B, like that of all viruses, is difficult to establish.
The divergence of orthohepadnavirus and avihepadnavirus occurred ~125,000 years ago (95% interval 78,297–313,500). Both the Avihepadnavirus and Orthohepadna viruses began to diversify about 25,000 years ago. The branching at this time lead to the emergence of the Orthohepadna genotypes A-H. Human strains have a most recent common ancestor dating back to 7,000 (95% interval: 5,287–9,270) to 10,000 (95% interval: 6,305–16,681) years ago.
The Avihepadnavirus lack a X protein but a vestigial X reading frame is present in the genome of duck hepadnavirus. The X protein may have evolved from a DNA glycosylase.
The rate of nonsynonymous mutations in this virus has been estimated to be about 2×10−5 amino acid replacements per site per year. The mean number of nucleotide substitutions/site/year is ~7.9 x 10-5.
A second estimate of the origin of this virus suggests a most recent common ancestor of the human strains evolved ~1500 years ago. The most recent common ancestor of the avian strains was placed at 6000 years ago. The mutation rate was estimated to be ~10-6 substitutions/site/year.
Read more about this topic: Hepatitis B Virus
Famous quotes containing the word evolution:
“The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (1820–1903)
“Analyze theory-building how we will, we all must start in the middle. Our conceptual firsts are middle-sized, middle-distanced objects, and our introduction to them and to everything comes midway in the cultural evolution of the race.”
—Willard Van Orman Quine (b. 1908)
“Like Freud, Jung believes that the human mind contains archaic remnants, residues of the long history and evolution of mankind. In the unconscious, primordial “universally human images” lie dormant. Those primordial images are the most ancient, universal and “deep” thoughts of mankind. Since they embody feelings as much as thought, they are properly “thought feelings.” Where Freud postulates a mass psyche, Jung postulates a collective psyche.”
—Patrick Mullahy (b. 1912)