jonna wrote:Lets start with Genesis.
In the beginning, there was Adam and Eve who went on to give birth to Cain and Abel. And then there was the rest of the population.
Expound on those events.
The bible supposedly has the facts misrepresented. Part of the answer lies in mitochondrial DNA and i will just copy paste what others have written.
Well, put it this way. You are a genetic mix of your parents, each of which contributed half of your genetic material. They, of course, have gone through the same process and share an equal split of their parent's DNA. This means if you stop this back-tracking process with your grandparents, you are already a genetic mix of six distinct individuals who may have come from different regions of the planet.
Why is Mitochondrial DNA important?
But one factor remains constant – the mitochondrial DNA hasn't altered at all – it remains intact through the female line. Male sperm contains only enough mitochondria to power the sperm to the surface of the egg – it does not enter the egg. The egg, however, contains mitochondria that have been passed from mother to daughter for countless generations. The only way for mitochondrial DNA to alter is by natural mutations, which occur very slowly when compared with the almost frantic gene mixing we and our parents take part in.
How Does This Relate to an 'Eve' Concept?
Because the rate of mitochondrial genetic mutation is slow, it can be used as a clock to turn back time to a period before the mutations had crept in. When mitochondrial DNA from certain populations in Africa are sampled, they can be compared with European mitochondrial DNA. The mutation difference between the two populations can then be compared, and a 'clock' can be produced, enabling the rate of mutation in mitochondria to be established. This produces a time-scale which indicates when modern Europeans first left Africa.
The genetic survey that produced the whole Mitochondrial Eve scenario didn't just sample Africans and Europeans – it sampled genes from people all over the planet. When mitochondrial DNA was compared, the survey discovered a startling result. Fundamental similarities in mitochondrial DNA in living humans suggested that we all contain genetic material from a single woman who was living in Africa around 200,000 years ago.
How Could a Single Being Populate a Planet?
And this is where the confusion sets in. A single organism can't populate a planet (arguments about amoeba aside). The evidence didn't suggest a single woman living in isolation from members of her own species. What it suggested was a genetic bottleneck – a period in human history when the population was so small that the genetic expressions of a single woman could have an impact on all humans living on the planet today.
She didn't live alone – she would have lived within a community. She didn't just pump babies out, either. There is no reason to suppose that she had more than one female child. But there is reason to suppose that whatever female children she had, they contained specific advantages for survival over the rest of the population.
Why Was She So Successful?
The reasons are all around you. What makes us so successful? An ability to share ideas, to help one another in dire circumstances, a certain creative flair to overcome everyday problems. Or perhaps she introduced the ability to slaughter those who came between us and required resources. We, as her children, display all of these traits. It could have been something as simple as wanderlust – a yearning to see what lay over the horizon. They were perhaps more fertile, were more agile, more resistant to disease, or could throw missiles more accurately than anyone else around at that time. If you want to find out, then next time you're on a bus, or train, or walking down the street, look around you – look at the behaviour of your extended family.
Is Any of This True?
Well, yes and no. To get a completely accurate result the tests would have to be performed on every single person living on the planet today. The dates are in dispute, but the date is perhaps the least important point. Broadly speaking, populations do pass through bottlenecks. Eve had many ancestors – it helps if you think about her as an hourglass – she was the pinch in the glass through which our genes ran. There had been many more Eves before her, she is just our most recent common ancestor. There will probably be more population bottlenecks and more Mitochondrial Eves in the future.
Adam's a different story, he lived many years after Eve and he is explained by the Human Y-chromosome DNA.
Each male receives his Y-chromosome from his father. As with mitochondrial DNA, we can trace back the Y-chromosome DNA to the one man from whom all Y-chromosomes came. This Y-Chromosome Adam is thought to have lived approximately 50,000 years ago.6 It is possible to use our knowledge of Y-chromosome diversity to study human migration in ancient history. For example, all Y-chromosomes of individuals outside of Africa carry a particular Y-chromosome mutation called M168. Hence, all of these variant Y-chromosomes are descended from the single male in which this mutation occurred. Some men of African descent have the M168 mutation and some do not. This is evidence that a small group of humans left Africa and, through succeeding millennia, spread around the globe. Genetic diversity studies estimate that the migration from Africa occurred approximately 50,000 years ago, not too long after the existence of Y-chromosome Adam.
Implications for Human Ancestry
Mitochondrial Eve and Y-chromosome Adam lived at different times, were probably separated by thousands of years and quite possibly were in different locations. Thus, a pictorial diagram tracking all men’s Y-chromosome DNA would not trace back to the spouse of Mitochondrial Eve. Although coalescence does not indicate that all humans descended from a single couple, Mitochondrial Eve and Y-chromosome Adam are nonetheless the source of a portion of our DNA, namely the Y-chromosome DNA and the mitochondrial DNA. The rest of our DNA, located in the nucleus, comes from a large number of other ancestors. Looking at the total variation in the DNA of humans around the world, scientists have estimated that all our DNA came from an original population of several thousand individuals.8 This relatively small population size suggests there was at least one bottleneck — a period of time where the population was reduced significantly — from which our current human population expanded.