genetic drift

[knabe]

Do you have a reference?

For the knot reference, read Thor_Heyerdahl's book.

He was sort of an amateur anthropologist so his claim may be suspect.

 

[librarian]

aj, I was reading about something and tripped on the unfamiliar term " genetic load".
It's another interesting thing to try to understand.
https://en.m.wikipedia.org/wiki/Genetic_load

 

[aj]

Cool......thanks

 

[knabe]

Inbreeding

Inbreeding increases genetic load in the short run, but actually decreases genetic load in the long run. Overall, inbreeding increases the rates of homozygosity. In the short run, this means that offspring are more likely to get two recessive and deleterious alleles, so they will have lower fitnesses and experience an inbreeding depression. The result is that you could begin to weed out deleterious alleles, some scientists have gone so far as to claim that if a population begins to decline because of higher mutation rates then getting the remaining organisms to breed with their relatives will help push out some of the more harmful mutations. [/size]However, once the rate of the allele gets high enough the pairing frequency will get so high that it will start to weed out those alleles at a high rate since the organisms which get them will die before reproducing. This is referred to as a purging of the population as a result of inbreeding.

 

[librarian]

What doesn't kill us makes us stronger, I guess. But nature does not seem to favor inbred populations other than in dire circumstances. The human applications, sooner or later, have dire results.
Back to aj, I was in a World History class long ago and the main idea that held my interest was that the lasting contribution of Vikings was, that while viking around, they added a lot of outcross genetics to local populations and generally left a wake of heterosis behind them.

 

[aj]

It is fascinating to me to run the numbers on how the Americas were populated. Could say......100 people coming over the Bering strait 15,000 years ago......been the base for the native American population?

 

[knabe]

It is fascinating to me to run the numbers on how the Americas were populated. Could say......100 people coming over the Bering strait 15,000 years ago......been the base for the native American population?

did you do the calculation?

 

[aj]

I've seen models in various models on how it could have happened. I've got around 200 anthropological books here in the basement. If the environment was good and people were healthy with good longevity they could move south at say 70 miles a year and spread out over the continent surprising fast. There is the small problem with time frames because of the site in South America though.

 

[aj]

BOOK........Method and theory for investigating the peopling of the Americas.........edited by Robson Bonnichsen and D. Gentry Steele. Another good book by Dennis J. Stanford and Bradley........Across Atlantic Ice.

 

[librarian]

https://m.facebook.com/Palaeoblog

http://palaeoblog.blogspot.com/2012/05/book-review-across-atlantic-ice-origin.html?m=1

 

[aj]

There is thought that the early people of the America' and anywhere.......were bearing children at the age of 13 with women dying at the age of 30 and men 45. I would argue that there was natural selection for pelvic area in humans over time. I talked to guy who was a medic in Vietnam way back when in the war. He decided to help the locals there by putting them on a vitamin program. Much to his dismay....the women actual encountered child birth problems because the babies were all just a little bigger. I think populations adjust through local environments through always being able to adjust through constant small mutations in genetics.