[Effect of secular acceleration on the human brain weight and its changes during aging].

The presented examinations on humans are based on 26 publications regarding the secular acceleration and 16 regarding the brain weight (each of the latter containing at least 500 values). The secular acceleration of the body length was only insignificant up to 1800 AD (about 1 mm per 100). From 1800 to 1900, the size of the length increased steadily and reached finally a size of 1 to 1.2 mm/a which is probably unchanged at present. This behaviour can be observed in every country in which such data were sampled. A positive correlation between brain size and body length can be found in a sample of about 11,000 values. An increase of 10 cm body-length corresponds to an increase of 59 g in brain weight, respectively 10 g brain weight are equal to 1.7 cm body-length. 21,300 values of 15 transversal examinations regarding brain weight and age compare the brains of the older and smaller generation having primarily smaller brains with those of the younger generation having primarily larger brains. Therefore the observed diminution of the brain weight during ageing is partly fictitious. With the help of correlation between brain weight and body length on the one hand and the secular acceleration of the body length on the other hand it is possible to correct the fictitious part of this diminishing. The result can state that the real diminution of the brain begins around the 60th year of age. However, it is probable that a high individual variability concerning time and speed exists. At present, the ideas regarding the sources of the secular acceleration are highly speculative.