America Will Never Be A Secular Society

real life wrote:

Do you agree with the science that indicates all living humans are descended from the same line?

What do you think I think RL? (I just thought I would play your game for a while. Let me know when you get tired of it)

I don't think ros is upset. He simply misunderstood what my question was referring to.

Yes, we all come from the same line. Now, the tricky part is defining what "line" is. I think of it as a single small tribe/family unit.

As far as the MRCA thing is concerned, could someone please post a link or article explaining this?

MRCA of all living humans

The existence of an MRCA does not imply existence of a population bottleneck or first couple[/i]. The MRCA of everyone alive today could have co-existed with a large human population, most of whom either have no living descendants today or else are ancestors of a subset of people alive today. This seemingly paradoxical phenomenon can be easily explained, if the nature of lineage is taken into account.

When tracing human lineage back in time, most people look at parents, grandparents, great-grandparents and so on. The same approach is often taken when tracing descendants via children and grandchildren. This approach is misguided, as the numbers of ancestors and descendants grows exponentially as generations are added to the lineage tree. In 80 generations, the number of ancestors is 280, more than a trillion trillion.

This simple calculation does not take into account the fact that every fertilization is really a fertilization between distant cousins. The ancestry tree is not really a tree, but a directed, acyclic graph. One can place all living people at the bottom of the graph and ancestors above their descendants. Starting with the bottom row of living people, one can add their parents on top of the existing row. Some parents have more than one child, thus some people become connected via a common ancestor, their parents. As each generation of ancestors is added at the top of the graph, more and more people become related to one another (first cousins, second cousin, third cousins and so on). Eventually, one of the many top-level ancestors will eventually become the MRCA from whom it is possible to trace a path of direct descendants all the way down to every living person at the bottom of the graph.

It is incorrect to assume that the MRCA passed all (or indeed any) of his or her genes down to every person alive today. Because of sexual reproduction, at every generation, an ancestor only passes half of his or her genes to the next generation. The percentage of genes inherited from the MRCA becomes smaller and smaller at every successive generation, as genes inherited from contemporaries of MRCA are interchanged via sexual reproduction.[2]

Yes, we all come from the same line. Now, the tricky part is defining what "line" is. I think of it as a single small tribe/family unit.

As far as the MRCA thing is concerned, could someone please post a link or article explaining this?

There's no particular reason the laws of nature that we find on Earth should also govern a star billions of light years away.

Ummm... no?

Your claim that science is coming around to the view that all living humans are descendants of one person is patently absurd. No scientist worthy of the title would make that claim. From what I've read of MRCA since this topic came up, it seems to me like science is slowly agreeing that modern humans all came from a single group or tribe at some point in the past

fungotheclown wrote:

Ummm... no?

Your claim that science is coming around to the view that all living humans are descendants of one person is patently absurd. No scientist worthy of the title would make that claim. From what I've read of MRCA since this topic came up, it seems to me like science is slowly agreeing that modern humans all came from a single group or tribe at some point in the past

http://en.wikipedia.org/wiki/Mitochondrial_Eve

The existence of Mitochondrial Eve and Y-chromosomal Adam does not imply the existence of population bottlenecks or a first couple. They each lived within a large human population at a different time. Some of their contemporaries have no living descendants today, and others are ancestors of all people alive today. No contemporary of Mitochondrial Eve or Y-chromosomal Adam is an ancestor of only a subset of people alive today, because both of them lived much longer ago than the identical ancestors point.

real life wrote:

fungotheclown wrote:

Ummm... no?

Your claim that science is coming around to the view that all living humans are descendants of one person is patently absurd. No scientist worthy of the title would make that claim. From what I've read of MRCA since this topic came up, it seems to me like science is slowly agreeing that modern humans all came from a single group or tribe at some point in the past

http://en.wikipedia.org/wiki/Mitochondrial_Eve

The link RL posted wrote:

The existence of Mitochondrial Eve and Y-chromosomal Adam does not imply the existence of population bottlenecks or a first couple. They each lived within a large human population at a different time. Some of their contemporaries have no living descendants today, and others are ancestors of all people alive today. No contemporary of Mitochondrial Eve or Y-chromosomal Adam is an ancestor of only a subset of people alive today, because both of them lived much longer ago than the identical ancestors point.

... just so we're all clear on what and MRCA means...

Science is coming round to the view that all living humans are descendants of one person that lived fairly recently.