Y Chromosome Data

Study Total
Base
Pairs 
95% CI Mean Est.
Pop.
Size
Lower  Upper
Dorit,
et al.
27,702  0 800,000  270,000  7,500
Hammer 39,000  51,000  411,000 188,000 5,000
Whitfield,
et al.
91,500  37,000 49,000 43,000 N/A
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Slide 31 of 109


In 1995, scientists have examined human origins from the perspective of male genetics (1, 2). Scientists have examined a gene (ZFY), which being on the Y chromosome, is passed down only from father to son. Thirty-eight men were chosen from all over the world (Africa, Asia, Australia, Europe, and Northern, Central, and South America). Scientists determined the actual genetic sequence in each man for this gene, which is 729 base pairs long. To their surprise, all men had identical genetic sequences (over 27,000 base pairs analyzed). Scientists have calculated the most probable date for the last common ancestor of modern man, given the sequence diversity from modern apes. Using two different models this date is either 270,000 or 27,000 years ago. However, both these models assume that the male population during this entire period of time consisted of only 7,500 individuals. The date estimates from these models would be significantly reduced if the male population were higher than 7,500, which is very likely. Two separate studies using similar techniques looked at larger pieces of the Y chromosome, which would reduce the uncertainty in the calculation of dates. One study examined a gene which was 2,600 base pairs and determined a last common ancestor date of 188,000 year ago (minimum of 51,000 and maximum of 411,000 years ago) (3). The other study used a very large piece of the Y chromosome (18,300 base pairs) and calculated a last common ancestor date of modern man of 43,000 years ago (minimum of 37,000 and maximum of 49,000 years ago) (4).


Definitions

CI (Confidence Interval)
A statistical measure of the certainty of a value. 95% CI means that there is a 95% probability that the true result lies between the CI values.

References Top of page

  1. S. Paabo. 1995. The Y chromosome and the origin of all of us (men). Science 268: 1141.

  2. R.L. Dorit, H. Akashi, W. Gilbert. 1995. Absence of polymorphism at the ZFY locus on the human Y chromosome. Science 268: 1183.

  3. Hammer, M.F. 1995. A recent common ancestry for human Y chromosomes. Nature 378: 376-378.

  4. Whitfield, L.S., J.E. Suston, and P.N. Goodfellow. 1995. Sequence variation of the human Y chromosome. Nature 378: 379-380.


Last Modified June 21, 2006