If peoples of same race, because great disaster, are isolated in different continents, how long shoud be...?

Question

necessary to their descendents become different races?

Answer 1

Speciation is similar to races developing.  For a species to split into two species, generally what is necessary is for them to be divided into at least two populations.  That way, they can develop separately. If there was a factor such as intense heat and sun, developing darker skin might be relatively quickly evolved (maybe a couple thousand years to make some noticeable change).  Things that have a very marginal benefit might take an extremely long time, upwards of hundreds of thousands of years or more.

Answer 2

very long for skin pigment to change due to genetic mutations

Answer 3

There is no answer to that question!  It's like asking how long a piece of string is!

Answer 4

There is no such thing as race.

In the case of a specific gene, for example, eye colour... it would depend on the size of the initial colonists and the diversity of genes for this attribute.

In the case of say 4 colonists, inbred for approx 3-6 generations, you would expect that they would lose a lot of their genetic diversity and have certain characteristics in common... trouble is that they would be based on the characteristics of the initial colonists, plus any mutations - which are very rarely beneficial and more likely to give them a problem.

Answer 5

Native Americans are pretty distinctive to Asians after about 10,000 years.

Yadda yadda race doesn't exist. If it doesn't exist, how come they can tell you your ancient geographic race with a DNA test? They can even nail the country of origin in many cases.

You'd need a small founder group, say at least 30 breeding pairs, and 50 to be sure to keep going.  It would also depend on how different this random group was from the norm, as a 'founder effect' can quickly cause a difference to the other people.

If you had two massive groups of genetically similar people in a similar but separate environment, I'd be looking at hundreds of thousands of years before any significant differences.

AND RACE DOESN'T MEAN SPECIES! AARGH!

Look it up, it means a noticably different inbreeding population of the same species.