natural history of ashkenazi intelligence - Henry C Harpending ...

Ashkenazi intelligence 15
The standard errors of all the values on the diagonal, estimated by bootstrapping, are
slightly less than 4.
The off-diagonal entries in Table 1 are genetic distances, statistics describing how
different the pairs of populations are from each other. The biased distances were
computed as:
dij � �alleles (pi�pj )2
p(1�p)
�
alleles
where the p i and p j are allele frequencies in the two populations and p=(p i+p j)/2
(Cavalli-Sforza et al., 1994). These distances are biased because of the binomial
variance associated with finite samples from the populations: two samples from the
same population would yield a positive distance. The unbiased distances in the lower
triangle of the table were computed by subtracting the average of 1/2N i+1/2N j, where
the Ns are the sample sizes from each population. The unbiased distances should be
used to compare these data with theory or with distances from other populations, but
the biased distances are of more interest in this paper. They can be compared with
the results of our simulations, since the simulations are of the same number of loci
and the same sample sizes as the data. Bootstrapping shows that the standard errors
of the biased distances in the table are about 2.
The important datum for evaluating the bottleneck hypothesis in Table 1 is the
genetic distance between mixed Europeans and Ashkenazim: Ashkenazim are nearly
as similar to mixed Europeans as Russians are, and the differences are easily within
the range of sampling error. From the perspective of a large collection of largely
neutral genetic variation Ashkenazim are essentially European, not Middle Eastern.
This small genetic distance from a large collection of markers is crucial evidence
that denies the bottleneck hypothesis for the Ashkenazi disorders. Simulations (below)
show that either there was low gene flow into the Ashkenazim and no bottleneck else,
if there was a significant bottleneck, subsequent gene flow was so high that it erased
the effects of the bottleneck. In either case drift could not have been strong enough
to allow deleterious mutants to increase to high frequencies.
The small genetic distance between Ashkenazim and other Europeans also shows
that patterns in neutral markers may not be informative about biologically meaningful
differences among populations. The genetic distance between Ashkenazim and
other Europeans computed from IQ is roughly one hundred times greater than the
distance from polymorphic markers.
Evidence from rare genes
Even though gene frequencies in Ashkenazim are nearly indistinguishable from
mixed Europeans overall, there are clear genetic signatures of the Middle Eastern
ancestry of the population and of shared history with other Jewish groups.
Factor XI deficiency is a bleeding disorder. Usually mild, it can become serious
after injury, surgery or childbirth. It is partially dominant: 20–50% of carriers (not
just homozygotes) also experience excessive bleeding. It is rare in most populations
but quite common among Ashkenazi Jews: the gene frequency is about 5%.