Archaeological evidence regarding the health and population density of human beings and their dietary habits. Inference from surviving examples.
This isn't necessarily evidence against a Malthusian equilibrium. It could be that the subsequent farmer lifestyle enabled survival for people with much poorer health and physical fitness, thus lowering the average health and fitness of those who managed to survive in the Malthusian equilibrium.
Can you give a reference that specifically discusses how a non-Malthusian situation of the foragers can be inferred from the existing archaeological evidence?
The observatiion that the traits generally associated with the Malthusian trap are common experiences of agricultural societies and dependent upon conditions that don't obtain in predominantly and purely hunter-gatherer societies.
This is not true. Humans are (more or less) the only species that practices agriculture, but the Malthusian trap happens to non-human animals too. As long as reproduction above the replacement rate is possible, it will happen until the resource limit is reached. (Admittedly, for animals that aren't apex predators, the situation is more complicated due to the predator-prey dynamics.)
Regarding the foragers' supposed cooperation on keeping the population stable, I honestly don't see how what you write makes sense, for at least two reasons:
The defectors would not need to reproduce in blatantly extraordinary numbers. It would be enough to reproduce just slightly above the replacement rate, so slightly that it might be unnoticeable for all practical purposes. The exponential growth would nevertheless explode their population in not very many generations and lead to them overwhelming others. So even if we assume that blatantly excessive reproduction would be punished, it would still leave them more than enough leeway for "cheating."
How did this punishment mechanism evolve, and how did it remain stable? You can postulate any group selection mechanism by assuming altruistic punishment against individuals who deviate from the supposed group-optimal behavior. But you can't just assert that such a mechanism must have existed because otherwise there would have been defection.
Moreover, you are now talking about group selection with altruistic punishment. There's nothing inherently impossible or absurd about that, but these are very strong and highly controversial claims, which you are asserting in a confident and authoritative manner as if they were well-known or obvious.
Estimates of world population growth come from:
http://faculty.plattsburgh.edu/david.curry/worldpop.htm
Essentially human for our first 2 million years of existence, human population worldwide went from about 10,000 to 4 million. Given that virtually all major models of long-run human population converge very closely, and they all assume a relatively steady growth rate, we're talking a doubling period of 250,000 years.
Malthus' estimates assume a doubling rate of 25 years, or a single human generation. The difference is a factor of 10,000. World population s...
From Mike Darwn's Chronopause, an essay titled "Would You Like Another Plate of This?", discussing people's attitudes to life:
Conclusion, graphs, and references in article. As usual, I recommend reading Chronopause.com as Darwin has many good articles; to quickly link a few: