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Evolution/Human Migration

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Question
Hi,
  I have a question I am hoping you can help me with. If you do don't have a definitive answer, no problem, I will be just as perfectly happy to get your educated opinion on the matter.
Ok my question has to do with ancient human settlement and migration of South America.
I do not believe in most of the "Ancient Alien" Stuff and conspiracy theories. However I do believe that in the many different Ancient Alien theories out there and on the Tv Show there a bits and pieces of real possibilities of things that have a ring of truth. Not that they really are connected to aliens but that the actual history is different than what we currently tend to believe. The problem is that those few things are scattered throughout a bunch of nonsense. they link things together that dont make sense.. So the good is lumped in with the bad.
Anyway my point in stating all that is that I believe that South America and central America at least parts of it was then had humans long before commonly thought. How long before, well not sure. However
So everytime I hear someone say that just for example that boats werent advanced enough to sail the pacific say 20,000 years ago, it bugs me. I get their point but my thoughts are what if for example a tribe of humans  from the japan area or Malaysia or something are out fishing or whatever they would use their boats forin simple boats and a storm takes them out to sea. Is it really so hard to believe that some could just by luck end up crossing the Pacific and settling in South America? I mean even today you hear about the fisherman or tragedy survivor who survives for many months just floating till they hit shore.
Maybe some set out not knowing what was out there, thinking it would come sooner and then having to just carry on till they find shore.
Anyway that long winded rant was to ask what may be a very simple question.
How many people would be needed in a village or settlement in order to not eventually go extinct?
Did the humans back then care about inbreeding?
Anyway I was just thinking that if too many people are needed then that may shoot that theory right to heck, so I am curios to know how low the number is. Thanks

Answer
Dear Jason,

Though there will always eventually be inbreeding with a small founder population, that won't necessarily be a problem if harmful alleles are weeded out of the population through natural selection.  Purifying selection can drive even a very small population to survive, if conditions are right and the members of the population are lucky.

Theoretically, all you need is two founders:  a male and a female.  Yes, the offspring will be inbred.  But that is not necessarily fatal, as long as there are sufficient offspring to allow for fatalities.

It would not be very LIKELY that two humans could start an entire civilization, but it's not impossible.

Dana

Evolution

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Dana Krempels

Expertise

I can answer questions about evolutionary mechanisms and theory, including genetic drift, mutation, natural selection, etc. I also can clear up misconceptions about evolution as it's sometimes talked about by those not well-versed in the subject (e.g., some politicians and many religious fundamentalists).

Experience

I have a Ph.D. in Biology, and presently teach Evolution and Biodiversity, Genetics, Botany, and Zoology at the University of Miami.

Organizations
House Rabbit Society Beta Beta Beta Biological Honor Society

Publications
Exotic DVM Magazine (veterinary journal)

Education/Credentials
B.S. in Biology B.A. in English Ph.D. in Biology

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