Written in 2003; 1,354 words; 26 sources; APA; $ 45.95
Paper Summary:
This paper highlights difficulties with using sequence data to estimate parameters about human ancestral populations, particularly times of speciations (when new species evolved). The Y chromosome has been analyzed to infer various parameters about human ancestral populations and to provide clues as to human origins. The paper argues that the individual properties of this data source combined with a burgeoning list of refutable assumptions make any and all of these results utterly spurious. The paper argues that molecular experts claim that the old and imprecise science of paleontology has been superseded by their far more mathematically precise methods. These experts sideline the fact that all their estimates are fundamentally based on paleontologically acquired data. The paper includes illustrations and table.
From the Paper:
"The Y-linked SRY gene triggers mammalian male-determining processes when expressed in the embryonic bipotential gonad. Sex chromosomes are thought to have evolved ~300Mya, probably replacing a mechanism based on gestational ambient temperature. Current opinion is that the Y-chromosomal SRY gene and its X-chromosome homologue (SOX3) are variants diverged from an ancestral non-sex-determining gene. When the ancient SRY-precursor gene gained a dominant and penetrant male-determining function the homologues became sex chromosomes and the process of dramatic degeneration and specialisation of the Y began. Pseudoautosomal regions (PARs) located at the tips of X and Y recombine at high frequency during male meiosis. Consequently, these regions are similar to autosomal sequences in base composition and gene diversity. PARs comprise 5% of the Y and the other 95% makes up the non-recombining region of the Y (NRY). Recombination deficiency of the NRY is thought to result from lack of homology with the X, due to several large inversions. Null mutations accumulate in NRY genes as they are "sheltered" by X-chromosome homologues."
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