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![]() ![]() ![]() ![]() ![]() ![]() ![]() First | Previous | Next | Last | | Index | Home 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
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Last Modified June 21, 2006