Jensen, A. R. (1969). Reducing the heredity-environment uncertainty. Harvard Educational Review, 39, 449—483. Reprinted in: Environment, heredity, and intelligence. Harvard Educational Review, Reprint Series No. 2, 1969. Pp. 209—243.
Crow states that because of unidentified environmental influences height has increased by a “spectacular amount.” And Hunt, on the basis of what he heard from guides at Jamestown’s Festival Park and aboard the U. S. Constitution, states that height “appears to have increased nearly a foot without benefit of selective breeding or natural selection.” Presumably Hunt is referring to the increase in adult height since about the 17th century. The implication is that all of this increase in height is strictly the effect of environmental and not genetic factors.
Let us see what more dependable authorities than tourist guides have to say about this subject. I have obtained my information from a book on human genetics by a noted British geneticist (Carter, 1962), and from comprehensive articles on this subject by J. M. Tanner (1965, 1968), the world’s leading researcher on human growth. Here is what I find:
First of all, it is essential to distinguish between growth rate and final (adult) level. Adult height has increased little over the past century or so. Carter (p. 102) says that skeletal remains suggest there has been little appreciable change in height in Britain over the past 5000 years. “If there has been any increase [in adult height in Britain] it is only of the order of 1 inch. What environmental improvements appear to be doing is, in the main, to accelerate growth, so that full adult height is being reached earlier. Records from the armed services, prisons, and anthropological surveys suggest that full adult height has not changed by more than i-/2 inches for the past century” (p. 102). Other countries have shown slightly higher increases than in Britain, and Tanner (1968) concludes that adult height has increased 2-1/2 to 3-1/2 inches in the past century. Increases before the last century were relatively minute. While the increase in height since about 1700 was a positively accelerated curve, it has become negatively accelerated in the 20th century, and the trend is leveling off, especially in the United States. Growth rate, and consequently children’s height, has shown much greater increases. Children now attain their full adult height by 18 or 19, on the average, rather than at 26, as was the case only 50 years ago. The trend toward earlier maturation shows up most dramatically in the lower age of menarche, or first menstrual period, which has declined from 17 to 13 years of age since 1840.
Jensen seems to be wrong. http://en.wikipedia.org/wiki/Human_height
However, if that was right, it might have relevance for the discussion of the FLynn effect, since e.g. Lynn likes to draw parallels to the concurrent growth in height.
Thoughts?
