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Author Topic:   All Human Beings Are Descendants of Adam
Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 100 of 118 (610170)
03-27-2011 7:03 AM
Reply to: Message 87 by Europa
03-26-2011 5:14 AM


Re: Becoming Human
So, ape-like primate to human being was a slow and gradual transition?
Yes, there may be specific features that we consider characteristic of humans that appeared rapidly in paleontological terms but the evolution of the whole suite of modern human characteristics would still have been gradual.
There was no single point at which we can mark the orgin of human beings?
As several people have pointed out there are probably several depending upon exactly what criteria you have for defining what constitutes a human being.
But suppose there was a single human being from which we all descended, will we not have an ME?
You still aren't adequately explaining what you actually mean by this. Are you suggesting a scenario where there was only one person alive on Earth, as has been pointed out sexual reproduction suggests this idea is wrong. Do you mean there were only 2 people as a founding breeding pair?
I have pointed out again and again that there are multiple sets of single human beings who can be traced as being ancestral to all modern humans. And as you go further back in time there will be similar sets for all of the preceding generations of humans, eventually you will reach a point where some of those common ancestors do no fit some definition of human.
Are these markers also present in everyone alive today?
Almost any gene can be used as such a marker. By looking at differences between currently extant alleles of a gene it's history can be reconstructed to determine the timing and sometimes the likely allelic type of the MRCA for that gene. This approach is based on Coalescent theory which I mentioned before.
I think you misinterpreted what i said. Yes I do mean we all descended from a single human being.
Again, as with everyone else, we don't want you just to keep repeating the same unclear statement over and over again, we want you to actually explain what you mean! By 'we all' do you mean all humanity forever or just all modern humanity?
Please try and explain yourself clearly. I understand you probably think you are already doing this but the fact that pretty much everyone else on this thread apparently misunderstands you suggests that this not the case.
TTFN,
WK
Edited by Wounded King, : No reason given.

This message is a reply to:
 Message 87 by Europa, posted 03-26-2011 5:14 AM Europa has seen this message but not replied

  
Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 101 of 118 (610172)
03-27-2011 7:18 AM
Reply to: Message 88 by Europa
03-26-2011 5:22 AM


Re: Becoming Human
If all human beings alive today have a particular gene (marker) and if this can be traced back to a point where it originated, it is only obvious that we all descended from that individual. No?
I think the problem is that you still don't really understand how this works. WE are all descendants of ME, but we don't all have the same mitochondrial genome as ME had. Instead we all have variants of that genome that have undergone distinct sequences of mutation.
What is done when calculating an MRCA is to use these differences to estimate how far back in time was the point at which the original allele from which all the variants originated existed. This doesn't identify any individual organism and it doesn't necessarily tell us what the ancestral allele or mitochondrial genotype actually was. It just gives us a time for when that particular allele existed.
You are correct though that the individual that possessed that allele would be a common ancestor of everyone alive today. This certainly doesn't mean that they were the sole common ancestor of everyone alive today.
This doesn't discount the possibility that the same allele wasn't prevalent in other individuals in the same population, just that if it was none of those individuals contributed their copy of that allele to the current gene pool. In the same way that none of ME's female contemporaries ended up contributing their mitochondrial genomes to today's gene pool.
TTFN,
WK

This message is a reply to:
 Message 88 by Europa, posted 03-26-2011 5:22 AM Europa has seen this message but not replied

  
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