Common Parent

by gravedancer 5 Replies latest jw friends

• 

  gravedancer

  I was driving home today and I had a thought (a totally new experience I admit). I think I can reconcile some of the answers to the thought but for some discussion here it is:

  Assumptions and logic chain

  • The population of humans is growing
  • The population of humans has gorwn over time
  • We could study history and create a growth curve over time to extrapolate a consistent growth rate
  • From that we could take the current human population of the planet and work backwards to the START of mankind

  Questions

  • Well, are these assumptions correct?
  • Which can be challeneged?
  • If we challenged some of them how would we ammend them?
  • If we acknowledge a START of mankind what does that mean?
  • Who were the immediate ancestors of the first person?
  • What about the first person would we classify to call them the first person vs a prehistoric being?

  While the questions seemingly pose an issue to an evolutionist, such as mine, I am not so sure they do yet.

  What are your thoughts?
• 

  JanH

  gd,

  Such an approach will not do.

  There has been no constant growth in the human population over time. Surely, in the last centuries there has been a steady increase, but not so in earlier times.

  As an example, from 1000BC to 1000AD the human population was more or less stable at around 300 million. It was kept in check by a very high child mortality, famine, diseases, wars and other causes of early death.

  When the population did start to increase, it was not because the birth rate went up, but because the survival rate increased, partly due to progress in agriculture. It's the same with the population increase in the last centuries, which really is exceptional in a historical perspective.

  - Jan
• 

  gravedancer

  Jan,

  Thanks for the chat earlier tonight. As we discussed Mitochondria Eve lies at the core of my answer.

  What does this mean? The premise of Mitochondria Eve is that we can all be traced back to a single woman about 200,000 years ago (probably in Africa).

  What are Mitochondria?Mitochondria power cells. Mitochondria are considered separate from the cell because they have their own DNA which is unaffected by other genetic exchanges.

  What are Mitochondrial DNA and why are they important?
  We are conceived by the combination of our parental genetic material (in equal proportion from each parent). Our paren'ts were conceived in the same manner from their parents contributing genetic material in equal proportions...and so on...in essence making us a "soup" of genetic material through multiple repeated patterns.
  
  However, the Mitochondrial DNA remain relatively consistent through the female line. Male sperm cells have only enough mitochondria to power them to the egg....but not enough to enter and mix with the mitochondria from the female egg. Thus the only possible way for mitochondria to change in makeup is through mutation (a slow drawn out process)

  What does this have to do with "Eve"?
  By comparing the Mitochondrial DNA from different groups, from different regions we can construct a "molecular clock". For example if we pattern the Mitochondrial DNA (MDNA) from someone in Africa and then compare it to the MDNA of someone say from Europe we can ascertain when the Europeans left Africa. The sampling as part of the survey to construct this theory occurred from hunderds of groups from all over the planet. When the data was analysed it pointed to a common ancestor living in Africa about 200,000 years ago.

  This points to a glut in human genetics at which point the earthly population was so tiny that the genetics of one woman could affect all future population. She must have had genetic advantages which enabled her offspring to survive while all other offspring from other parents died over time thus leaving her MDNA as the consistent fabric across time.

  She may not have been the last Mitochondrial Eve....
• 

  funkyderek

  This points to a glut in human genetics at which point the earthly population was so tiny that the genetics of one woman could affect all future population. She must have had genetic advantages which enabled her offspring to survive while all other offspring from other parents died over time thus leaving her MDNA as the consistent fabric across time.

  No gravedancer, that's not the case. She was not the only female of her time to have surviving offspring; she was the most recent female ancestor of everyone alive today in a purely matrilineal line. That such a person must have existed is mathematically provable, but that in itself tells us nothing about when she existed or how many humans were alive at that time.

  The differences in MDNA in the population tell us that she lived between 100,000 and 200,000 years ago, most probably in Africa at which time she would not have stood out in any way from the population. At the time, a different long-dead person would have carried the title of "Mitochondrial Eve."

  Most of the confusion lies in the moniker given this woman. She was not the only woman alive at the time, or in any significant way different from her contemporaries, except in retrospect. She was certainly not the wife of "Y-chromosome Adam", our common ancestor in a purely patrilineal line, who appears to have lived many tens of thousands of years later.
• 

  gravedancer

  FD - thanks for responding. I never meant to imply that she was the only living woman at the time...

  Its an interesting thought though:

  How could someone else have preceded her as Mitochondrial Eve? Where would the current title holder have obtained her MDNA from?

  I have studied the theory but still have some issues making sense of it.
• 

  funkyderek

  How could someone else have preceded her as Mitochondrial Eve? Where would the current title holder have obtained her MDNA from?

  Mitochondrial Eve is the most recent ancestor in the purely female line. She is not the only one. (Her mother, grandmother etc.) At the time she was alive, she was obviously not an ancestor of everyone living, one of her female ancestors would have held the title. She got her MDNA from her mother, same as the rest of us. Remember, the title of "Mitochondrial Eve" is a retrospective one. There must be a most recent common matrilineal ancestor of everyone alive, who it is depends on who is alive at the time.

  I have studied the theory but still have some issues making sense of it.

  It's a difficult one, and the name Eve probably only adds to the confusion, as do press reports that the idea of Mitochondrial Eve is somehow startling or in itself newsworthy. That such a person existed is a certainty. The only question is where and when.

  Here's a useful web site on the subject:

  http://www.talkorigins.org/faqs/homs/mitoeve.html

  and believe it or not:

  http://www.answersingenesis.org/docs/4055.asp also provides a very good explanation although, unsurprisingly, questions the accepted dates.