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Mitochondrial Eve lived only 6500 years ago (Talk.Origins)

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Response Article
This article (Mitochondrial Eve lived only 6500 years ago (Talk.Origins)) is a response to a rebuttal of a creationist claim published by Talk.Origins Archive under the title Index to Creationist Claims.

Claim CB621.1:

Recent research shows the mutation rate in mitochondria much higher than previously thought [Loewe and Scherer 1997; Gibbons 1998]. The date of "Mitochondrial Eve," the common maternal ancestor of all humankind, was based on that mutation rate. The revised molecular clock indicates that she lived about 6500 years ago, not about 200,000 years ago as previously claimed.

Source: Wieland, Carl, 1998. A shrinking date for 'Eve'. Creation Ex Nihilo Technical Journal 12(1):1-3.

CreationWiki response:

(Talk.Origins quotes in blue)

1. The claim is founded primarily on the work of Parsons et al. [1997], who found that the substitution rate was about 25 times higher in the mitochondria control region, which is less than 7% of the mitochondrial genome (mtDNA). Revised studies of all of the mtDNA find that the control region varies greatly in substitution rates in different populations, but that the rest of the mtDNA shows no such variation [Ingman et al. 2000]. Using mtDNA excluding the control region, they placed the age of the most recent common mitochondrial ancestor at 171,500 +/- 50,000 years ago

What Talk.Origins is conveniently leaving out is that studies, like Ingman's, that yield dates for "Mitochondrial Eve" of about 200,000 years all base their mutation rates on the assumption that humans had a common ancestor 5 million years ago.

From the mean genetic distance between all the humans and the one chimpanzee sequence (0.17 substitutions per site) and the assumption, based on palaeontological and genetic evidence, of a divergence time between humans and chimpanzees of 5 Myr, the mutation rate (μ) for the mitochondrial molecule, excluding the D-loop, is estimated to be 1.70Times.gif10-8 substitutions per site per year. [Ingman et al. 2000]

This clearly shows that such dates are calculated by assuming evolution.

  • Gibbons [1998] refers to mutations that cause heteroplasmy (inheritance of two or more mtDNA sequences). This does not apply to mitochondrial Eve research, which is based only on substitution mutation rates

WRONG! Gibbons (1998) only indicates that the discovery of high heteroplasmy rates led to the study. It is clear from the description of the measurements that it was substitution mutation rates that were being directly measured.

2. A study similar to the mtEve research was done on a region of the X chromosome which does not recombine with the smaller Y chromosome; it placed the most recent common ancestor 535,000 +/- 119,000 years ago [Kaessmann et al. 1999].

Kaessmann's date is once again based on the assumption that humans had a common ancestor 5 million years ago.

Assuming a divergence between chimpanzees and humans of 5 million years, a date based on both molecular and palaeontological evidence, approximately 1 substitution per 100,000 years will accumulate in these sequences. (Kaessmann et al. 1999)

  • Since the population size of X chromosomes is effectively three times larger than mitochondria (two X chromosomes from women and one from men can get inherited), the most recent common ancestor should be about three times that of the Mitochondrial Eve, and it is.

This assumes that all X chromosomes came from one X chromosome, but given the fact that all women have two and all men have one, it is more likely that they came from at least three original X chromosomes. This is what the Bible would indicate since Adam would have had one X chromosome and Eve would have had two X chromosomes.

When this is considered, the dates for these two most recent common ancestors becomes about the same as that for Mitochondrial Eve. So all this shows is that the error produced by using evolutionary assumptions is roughly proportional for both Mitochondrial DNA and X chromosome DNA. This would simply suggest that human and chimp mutation rates are similar for both Mitochondrial DNA and X chromosome DNA.

Reference: Mitochondrial Eve

When all of this is put together, the measured change in Mitochondrial DNA gives a date of the origin of man of about 6000 years. It is only by assuming evolution that one gets 100,000-200,000 or more years