In quantitative traits we have many loci affecting a trait. If we took a bunch of parents where all mothers and fathers were of a certain value at the upper end of a trait range, and then looked at the offspring would we expect offspring from pairs of parents from more divergent populations to be even more extreme variance in their traits?

For example: if we look at 2 men from East Africa, both 190 cm tall. They each have children with women who are 180 cm, one of whom is from East Africa and the other from Canada. We could assume that the Canadian woman is probably more unrelated to her male than the East African woman. I would therefore expect that it is quite likely that the East Africans in the example are tall because of "tall-alleles" in many of the same loci, whereas there is a greater probability that the Canadian female is tall thanks to mutations at different loci. Therefore would it be reasonable to expect greater variation in the offspring of the Canadian woman?

Is there any evidence of this phenomenon?

Note: Ignore environmental and gene * environment interaction variance, just go with a simple additive model, and assume populations have had some barriers to migration for some time

  • 1
    $\begingroup$ If I get you right, you might be looking for something like heterosis (en.wikipedia.org/wiki/Heterosis)? Although mostly described for animals and plants, the principle should basically apply to sufficiently distinct human lineages as well. $\endgroup$
    – ChrKoenig
    Oct 23, 2014 at 7:37
  • $\begingroup$ Yes, the MHC example there is quite relevant @Hav0k $\endgroup$
    – rg255
    Oct 23, 2014 at 7:45
  • $\begingroup$ If being tall is beneficial, the "tall" loci are probably (partially) dominant and therefore, two tall parents from different origin may be expected to have taller offspring than two parents from the same origin. It seems hard to me to draw such general conclusion as it really depends on the number of loci under consideration, on the pattern of dominance and on whether the parents are homo or hetero zygous (and on epistasis). $\endgroup$
    – Remi.b
    Oct 24, 2014 at 18:20
  • $\begingroup$ If we assume that the parents are both heterozygous (for all loci under consideration) and all loci are bi-allelic and allele are additive, and parents are of any size, then indeed I would expect that the offspring from the parents form different origin will have higher range o possible genotypes. I am not sure my comments can help :) The question is very interesting +1 $\endgroup$
    – Remi.b
    Oct 24, 2014 at 18:20

1 Answer 1


Yes, it would be reasonable to expect greater variation in the offspring of the Canadian woman.

Human genetic variation is the genetic differences among populations. Populations have access a pool of genes and over-time polymorphisms may arise to create greater variation.

Human populations within a species are defined by, divergence times and rates of gene flow - From mitochondrial, X and Y chromosome re-sequencing data.

Genetic Distance is the genetic divergence between species or between populations within a species (as in your example above). Populations with many similar alleles have small genetic distances. This indicates that they are closely related and have a recent common ancestor.

E.g. Height as you use for your example is a polygene. The inheritance of many genes alter phenotypic height of offspring.

Thus, it would be reasonable to expect a difference in allelic variations pertaining to height from the Canadian woman. The offspring may have a different height profile of alleles, and thus a different phenotypical height.

I should mention that:

"individuals from different populations can be genetically more similar than individuals from the same population"

But the above example - should not be expected.


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