The development of cumulative culture is due to climate instability?

Dated about 500 thousand years ago, we can find the first traces of tools much more complex of precedents, as consisting of several parts (like spears having the tip of stone or axes with an handle); these tools are also different according to the region and the time when they were produced and this shows that they were the result of a succession of changes made by different artisans. The accumulation of cultural mutations, a phenomenon first absent or exceptional, from then seems to become a fixed rule in human culture.
It  is ignored the cause of this very important change, but we know that hominids of this period show a further development of brain mass and changes at the base of the skull, making plausible a shift of the larynx and a modification of the voice.
 By an examination of the polar ice, it is also apparent with certainty that this historical period was characterized by great instability in the climate; relatively rapid changes alternated glacial to temperate periods and even within these periods there were great fluctuations in the average temperature; these sudden changes in the climate may have been a decisive impulse to fully exploit the cultural adaptability, much faster than genetic.
We can, however, note three important features of cumulative culture:
– it allows a more convenient and quick cultural adaptation, because changing existing instruments and customs is easier than creating new ones;
– the combination of simple cultural elements can form a wide variety of new solutions to new problems, just like the letters of the alphabet can compose a huge number of words, the evolutionary advantage is huge and brings cultural heritage to become, from a simple integration of the genetic heritage, the basis of later evolution;
– cumulative cultural innovations depend less and less by genetic mutations and increasingly from the accumulated previous cultural history; there is a tendency to greater autonomy compared to genetic heritage.
All this also had a cost: from the study of the bones we know that in the considered historical period, the time needed to reach maturity further lengthened to reach, with the Neanderthal man and today man, twenty years or so. This long period of apprenticeship requires to parents a greater sacrifice in terms of time and energy.

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