Thursday, August 08, 2013

Human Evolution: Neither Extreme Makes Sense

So what are we to believe concerning the origin of mankind?   What I see are two versions that don't seem to fit what we think we know about ourselves and the evidence.

The Bishop-Ussher Young Earth interpretation of Genesis and Numbers would have us believe that mankind is less than 10,000 years old, with a further constricting event (the flood) bottle-necking the population less than 5,000 years ago.   That's one extreme of course.  There are other ways of looking at those passages, and the meaning of ancient Hebrew words that would point to a somewhat older mankind, but not a million years older, nor even half-a-million.

This position does not fit a lot of historical evidence, and I don't feel like I even need to go into it here.  What I want to point out in this space is that the secular alternative on human origins seems to me, and many others, to be just as implausible.   For examples of why genetically their story does not make sense, see here.  Also consider this report, which says that the old figure of sharing 98% of our genes with chimps is off because it turns out we have hundreds of genes they don't have, and they have "lost" (if they ever had them) hundreds of genes which we have.   Not just new alleles in an existing gene mind you, but new genes.   How does that happen in the six or eight million years supposedly between us and chimps when we don't have even one solid instance of it happening in the history of modern humans ( a new gene - not just allele - being spread to every member of our species)?

Scientists tried to push the "multi-regional" model for human origins for a long time.  That is, humans evolved in several places at once over a long period of time from pre-human ancestors.   Once we learned how to do genetic testing, the evidence blew that one away in favor of the "Out of Africa Model" which said that humanity had a single point of origin in a time period that was too old for Young Earth Creationists to be comfortable with and too young for many evolutionary scientists to be comfortable with, say 120,000 years ago.

I think it part it was due to this discomfort that scientists made a major push to try and discover some ancient introgression of genes from non-humans into the human genome.  The very latest is that they have found some statistical evidence that such non-human hominids made a minor genetic contribution to our species, but only after we existed as a separate species.    This is not the same as the multi-regional hypothesis because mankind was a distinct group for quite a while before the genes from "near humans" made a limited insertion into our genes rather early in our history.  This part of the story is so recent that the jury is still out on the details.

They have closely examined the human genome and what they tell us about it boils down to this- all or virtually all of humanity can be divided into two distinct groups.   The founder group, the oldest and most genetically varied group, is best represented by the San or Kho-san of southern and eastern Africa.  There is the San, and then there is everyone else.  Sometime in the past three small groups of the San branched out and became everyone else.   One of those three groups, called L3, was the east African groups which today includes the Kenyans.   All the rest of the non-African populations are held to be subsets or offshoots of L3.

Here is the problem as I see it.  To calculate the time since all of these divergences, with the first divergence happening maybe 60-70 thousand years ago, they have to use a mutation rate.   The higher the mutation rate, the more recently all of these genetic splits occurred.    I have yet to see a study which uses current observed mutation rates as the standard.   They use mutation rates which are LOWER than the directly estimated rate we get when we compare a great-grand child today to his or her great-grand father.  

Why use lower rates than those which we actually observe, unless it is to push the estimated dates further back into the past to advance some other agenda?   If anything, I would think rates of mutation in the past would be HIGHER, not lower, because we are not out baking in the solar radiation all day like our ancestors and our time between generations is probably longer than it has been for most of human history.  But doing this would compress the time scale of the arrival of humans to a time so recent (still well beyond 10,000 years though) that there really would be nothing for them to evolve from.   That's kind of hard to get around, and we are not that far from that now.

But here is the kicker.  Think about the way humans get around.   Think about what has happened in the world in all of known history.    The current scientific model would have us believe the San bounced around south and east Africa with groups L1, L2, and L3 (who split off from the original San population) for 60,000 years before they started limited interbreeding again just a few thousand years ago.    That makes no sense whatsoever.   Especially if they are going to try and claim our ancestors had limited breeding with non-humans like Neanderthals at basically the same time.  Sixty thousand years is a long time for groups of modern humans to wander around the same continent and never re-connect.   It definitely does not fit what we know about humans in any way, and is frankly not believable.   The dates don't make sense, and I suspect they are wrong.


Blogger Mark Moore (Moderator) said...

That is an example of the schizophrenia in archeogeneology right now. That study claims the ancestors of modern Europeans came "after the last glacial maximum but before the Neolithic." OK, that is between 20 K years ago and 10,200 years ago- about half what the previous studies have said. Move that part of the picture up that much then why not move the whole picture up? Because it leaves modern humans coming from nowhere 50 or 60 K years ago when all possible things they could have evolved from were gone.

4:03 PM, August 12, 2013  

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