Linkage Disequilibrium

  • Human chromosomesHumanity originated less than 50,000 ya

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A study published in 1996 (1) examined linkage disequilibrium at the human CD4 locus (a T-cell associated antigen) as a means to establish the date of modern human origins. This study determined a maximum origin date of 102,000 years ago based upon the assumption that the Alu (-) alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one).">allele arose 5 million years ago, or almost immediately after mankind's split from other primates. As they stated, "It is likely that the Alu deletion event occurred more recently, in which case our estimates for the date of founding of the non-African populations would also be more recent." Preliminary studies from chromosomes 19, 11 and 8 show similar results to that seen on chromosome 12 (the locus of the CD4 gene) (2).


References Top of page

  1. Tishkoff, S.A., E. Dietzsch, W. Speed, A.J. Pakstis, J.R. Kidd, K. Cheung, B. Bonn-Tamir, A.S. Santachiara-Benerecetti, P. Moral, M. Krings, S. Paabo, E. Watson, N. Risch, T. Jenkins, and K.K. Kidd. 1996. Global patterns of linkage disequilibrium at the CD4 locus and modern human origins. Science 271: 1380-1387.

  2. Fischman, J. 1996. Evidence mounts for our African origins - and alternatives. Science 271: 1364.


Last Modified June 21, 2006