Archive | August, 2012

Implications of mitochondrial Eve for Human Evolution

9 Aug

It has been suggested that mitochondrial Eve is the most recent common matrilineal ancestor of all modern humans. This means to me that the mitochondrial genome of a single individual who lived 200,000 years ago is being put forward as the origin of all the patterns of mitochondrial DNA that are currently found in the human population worldwide. What are the implications of this statement?

My problem in grappling with this ‘computational discovery’ is that it seems to mean that the genetic pattern that this individual (mitochondrial Eve) represented went on to replace all other existing human genetic patterns worldwide, through outcompeting those variants to assert a kind of super-dominance, rather than doing the natural thing of choosing to interbreed with those other variants. This follows because interbreeding would have spread mitochondrial Eve’s particular DNA-sequence pattern among the rest of the Homo populations that existed such that the methodology for detemining the common ancestor would inevitably have lead to an earlier common matrilineal individual. And it is relevant to consider also that a replacement of other genetic patterns by the mitochondrial Eve pattern could only have been brought about physically by a sudden massive jump in evolutionary fitness 200,000 years ago which led to a vicious Homo lineage emerging that may be said to be the precursor of the modern Homo sapiens of 70,000 years ago. This lineage did not wish to breed with the rest of the existing Homo populations and may have set out to wipe out those parts of humanity through aggressive competition. What is the fossil evidence for this event? Secondly, there is not much apparent remnant of such an annihilistic behaviour in Homo sapiens in present day humanity which, on the other hand, demonstrates an overwhelming common culture of sympathy and goodwill for other sections of humanity and a demonstrable ready willingness to interbreed with other races and faces; this civility represents a distinguishing characteristic of most human beings that has highly selected for in the complexity of genetic speciation and selection pressures that is evident in human evolution.

An alternative explanation of human evolution deriving from the concept of mitochondial Eve is that no other human populations existed up to 200,000 years ago except for the genomics represented by this single individual. Does it make any evolutionary sense to state that the humanity of 200,000 years ago was of only a single DNA pattern, whatever this pattern was? If it was located in North or East Africa, what happened to the rest of the Homo ergaster-derived human populations that from fossil evidence we know had ‘speciated’ into Homo erectus and living between the Middle East to East Asia? Did all existing Homo species from 1.5 million years, excepting Homo floresiensis converge genetically into the DNA-pattern that is represented by mitochondrial Eve?

Accordingly, my question in this post concerns the tenability of these alternative scenarios as represented by the mitochondrial Eve ‘discovery’ (which in itself is a highly tenuos science in conception as already discussed). My aim in this blog is to stimulate contributions on what the standard (consensus) model, that is apparently mitochondrial Eve-based, means for how human evolution took place to bring about the ensuing population dynamics.

Is there anyone out there left who is willing to engage in this discussion?

The following was added to this post on 14 August 2012:

Further resources to be assessed in the light of what has been discussed in this blog are

(1) http://www.ncbi.nlm.nih.gov/pubmed/9468796

(2) http://www.ncbi.nlm.nih.gov/pubmed/16369961

(3) http://www.bbc.co.uk/news/science-environment-19423147

(4) http://www.nature.com/news/new-dna-analysis-shows-ancient-humans-interbred-with-denisovans-1.11331

Any review accordingly will be gratefully received at this blogsite.

The ‘founder effect’ for prehistoric human migration, colonisation and evolutionary descendence

1 Aug

My conclusion on the evidence submitted thus far is that Jokodo did not provide us with convincing reasons, given what Biologists know about how mutations take place in reality and how natural selection is supposed to have acted upon it in human history, that mitochondrial DNA and nuclear DNA generate a theoretical mechanism-based framework for designing genetic clocks that can reliably be used as models for ascertaining when prehistoric migration, colonisation and lineage descendance of humans took place over the past 2 million years through the so-called ‘founder effect’. Until such evidence is forthcoming the circumstantial evidence that East Asian Homo erectus survived and led to the modern Han Chinese population cannot be dismissed – this also despite the lack of the discovery of human fossils in China during 100,000-40,000 years ago that some might cite as evidence that an extinction of all existing humans had taken place around 100,000 years ago.