Among my main assertions: humanity might change the environment, but we do not fundamentally change; at least no quicker than any other species.
Add to the evidence a new study regarding the sleep patterns of hunter/gatherers compared to those of us enjoying the benefits of "progress."
From the Economist:
In total, the researchers collected 1,165 days’ worth of data. They found that people from all three groups slept for between 5.7 and 7.1 hours a day, with an average that hovered around 6.5 hours. Far from exceeding those of a modern city-dweller, these values are near the low end of the range found in industrial societies. An average 7.5 hours a night is the norm there.
Nor did the Hadza, the Ju/’hoansi San or the Tsimané retire shortly after the sun went down. Rather, they stayed awake for an average of 3.3 hours after nightfall, much as people in the developed world do. Their bedtimes appeared to be regulated by the temperature, rather than by daylight, and it takes several hours after the sun has set for things to cool down.
The study also calls into question the idea that siestas are a feature of human behaviour that has been suppressed by modern ways of life. The volunteers rarely napped in summer (doing so on about one day in five), and almost never in winter.
One difference they did find was that the pre-industrial people studied rarely suffered from insomnia.
So much for progress.