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Evolution 2nd Edition

Evolution (2nd Edition)

Book Edition2nd Edition
Author(s)Bergstrom, Dugatkin
PublisherW. W. Norton
Section 19.3: The Emergence of Anatomically Modern Humans
Section 19.5: Migration of Modern Humans

Chapter 19, Section 19.3, KEY CONCEPT QUESTION, Exercise 19.1

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It can certainly not be concluded that the sole reproductive female that has given rise to the entire population was individual mt. E. Through the maternal line, the mtDNA [mitochondrial deoxyribonucleic acid] passes down the generations [from one to another; mother passes mtDNA to the offspring, that is, both females and males; the females further pass the mtDNA to their offspring, but males cannot]. The mitochondrial locus [a particular position on the chromosomes where specific gene is present] in itself is a single non-recombining [does not undergo recombination, that is, a process in which the genetic material is exchanged either between separate regions in the same chromosome or among different chromosomes] locus via which the complete [whole] genome of an individual cannot be considered or examined.


According to the coalescence theory, all the alleles present currently at a given locus merge down to a single allele or an ancestral copy present at a certain point in the history, irrespective of the growth or size of the population. mt. E remains to be the only female individual in whom all the human being's [living] mtDNA merged, which is why mt. E became the recent common ancestor for that particular locus. However, this does not remove the possibility of the existence of other reproductive females in the ancestral period. It is possible that their mitochondrial genes just could not pass constantly or uninterruptedly in the future generations [referring to those living in present times].

Verified Answer

The individual mt. E can only be considered as all human being's maternal recent common ancestor at a single locus [refers to a particular position on the chromosomes where specific gene is present], that is, mitochondrial gene locus [because all mitochondrial genes originate from one locus], but not the other genes [including nuclear genes]. According to the coalescent theory, mt. E was the individual that harbored the coalescence. Indeed, there would have been other reproductive females also, but they are out of picture because of the failure in continuously passage of the mitochondrial chromosomes down the generations that live in the present times. 

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