# A Mathematical Analogy to the Genetic Inheritance of Intelligence

by David Sims

LET ME INDULGE in a bit of math to show how a normal distribution can arise from biological inheritance.

Suppose that there are ten locations on the human DNA that pertain to intelligence. I don’t know how many such locations actually exist, but for the purpose of illustration, let’s assume that there are ten.

Suppose, further, that there are 11 different alleles (variants of a gene) that would be candidates to fit on each of those ten locations on a strand of human DNA. I don’t know how many such alleles actually exist, but we’ll assume for the sake of argument that there are eleven of them for each location.

We’ll imagine that some of these alleles are more potent in creating an intelligent brain than are some of the others. Indeed, we’ll assume that one of the alleles that can occur in a location will contribute no IQ points at all. This allele is a dud.

The second of the alleles that can occur at the same location provides 2 IQ points; the third provides 4 points; the fourth contributes 6 points; the fifth contributes 8 points; the sixth contributes 10 points; the seventh provides 12 points; the eighth grants 14 points; the ninth applies 16 points, the tenth bestows 18 points, and the eleventh and strongest allele kicks in 20 points.

If, by an amazing coincidence, a person inherited at conception the most potent allele at all of the intelligence spots on his DNA, he’d have an IQ of 200 and be a super-genius. But, of course, that isn’t very likely.

Just for example, suppose that, at conception, a member of Race A has a 9% chance of getting any of alleles #1-#5 or #7-#11 and a 10% chance of getting allele #6 at each of the ten locations. A random sample of one million individuals from Race A might have this spread of IQ:

Race A.
n=1000000
average IQ = 100.0
IQ range, number individuals in range:
0 to 10, 0
10 to 20, 7
20 to 30, 55
30 to 40, 671
40 to 50, 3724
50 to 60, 14606
60 to 70, 40997
70 to 80, 87945
80 to 90, 114389
90 to 100, 187760
100 to 110, 191867 ← biggest bin
110 to 120, 155869
120 to 130, 98898
130 to 140, 48651
140 to 150, 18460
150 to 160, 5012
160 to 170, 969
170 to 180, 113
180 to 190, 7
190 to 200, 0

That was from an actual computer run using a random number generator. The random numbers were without weighting, but the way they add up produces a normal distribution.

Suppose again that members of Race B has an 11% chance of getting any of alleles #1-#6, a 10% chance of getting allele #7, and a 6% chance of getting any of alleles #8-#11 at each of the ten locations. A random sample of one million individuals from Race B might have this spread of IQ:

Race B.
n = 1000000
average IQ = 85.8
IQ range, number individuals in range:
0 to 10, 1
10 to 20, 21
20 to 30, 456
30 to 40, 3709
40 to 50, 17788
50 to 60, 53662
60 to 70, 113931
70 to 80, 176219
80 to 90, 205926 ← biggest bin
90 to 100, 186466
100 to 110, 129347
110 to 120, 70351
120 to 130, 29718
130 to 140, 9648
140 to 150, 2313
150 to 160, 394
160 to 170, 47
170 to 180, 3
180 to 190, 0
190 to 200, 0

Now, of course, this is a very simplistic representation of genetic inheritance, using numbers instead of atoms and molecules. But the principle is about the same.

When leftists declare that all races share all alleles, they’re right. (Or almost right.) But then the lefties try to make that fact appear to mean more than it really does. The races share alleles for intelligence, but they don’t share them all equally. Some races have more of the premium quality alleles than other races do.

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