Kurdt said:
I do remember several months ago, a documentary concerning the missing link and current accepted theory (correct me if I am wrong) is that human ancestors developed the brain capacity we have now from the switch to consuming mainly plant life to a mix between meat and plant life.
At the end of this post is some information from another thread on the idea some people propose regarding increased protein causing increase brain capacity (not that this is what you or the documentary is suggesting). The essence of it is that increased caloric density (available through grains for instance) was what contributed to increased brain size.
I also seem to remember that the human body isn't completely incapable of dealing with meat. herbivores have a tough time digesting any meat, carnivores have similar trouble with vegetation omnivores can do both but aren't brilliant at either. I was under the distinct impression that we were the latter category of animal.
the key point you make is the "omnivores can do both but aren't brilliant at either". humans can eat meat, just as cats can manage vegetables and fruits, and factory farmed animals often end up being fed animal proteins in the form of 'rendered flesh', feces etc. every creature can be said to be omnivorous to some extent - but that doesn't mean it is a good idea. as for humans eating meat, the evidence accummulated over the past half century certainly indicates that it is a very bad idea.
Another thing that caught my attention is if we eventually deem it immoral to cull animals for food then what can we say about carnivores. Round them all up and feed them three bean soup?
the issue here is 'should we eat meat?' not 'should we allow any creature to eat meat'. i do not think the matter is simply one of morality though meat and dairy production can certainly be deemed to be immoral considering what goes on. the point is that since humans have no need to kill other animals for food (except in places where it is not possible to grow food), therefore eating meat can certainly be considered immoral given the circumstances.
in friendship,
prad
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the idea of large brain development being a result of the free hours for creative thought which became available as a result of the high caloric intake that meat supposedly provided is at best speculation.
However, the rationale behind some of this is perhaps interesting at least.
The idea is derived from the topic of encephalization reviewed (albeit somewhat biasedly) here:
http://www.beyondveg.com/billings-t/comp-anat/comp-anat-4a.shtml.
Essentially, the correlation between DQ (diet quality specifically the caloric intake) and brain size led to the hypothesis that in order to get all this energy, we needed to eat meat otherwise our brains wouldn't have ever developed. In fact, Leonard and Robertson claim that
What made meat an important resource to exploit was not its high protein content, rather, its high caloric return ... the early hunting-gathering life-way associated with H. erectus was a more efficient way of getting food which supported a 35-55% increase in caloric needs (relative to australopithecines)...
(If you recall, I mentioned the 2 human 'strains' earlier in the thread)
Their entire thrust appears based on dense caloric intake (as opposed to just meat) for later they write (Leonard and Robertson 1994, p. 79)
Even in human populations where meat consumption is low, DQ is still much higher than in other large-bodied primates because grains are much more calorically dense than foliage.
Having said all this, they conclude:
These results imply that changes in diet quality during hominid evolution were linked with the evolution of brain size. The shift to a more calorically dense diet was probably needed in order to substantially increase the amount of metabolic energy being used by the hominid brain. Thus, while nutritional factors alone are not sufficient to explain the evolution of our large brains, it seems clear that certain dietary changes were necessary for substantial brain evolution to take place.
Notice that they say that nutritional factors alone are not sufficient to explain brain development.
Note: there are several other theories such as the rather interesting one put forth by william calvin in the Ascent of Man deals with the ice ages and how human intelligence evolved as a result of having to deal with resulting challenges:
Three things apparently started 2.5 million years ago: the ice ages, toolmaking, growth in brain size.
Indeed, switches in climate may promote a jack-of-all-trades set of capabilities under some conditions. The rapidity of the climate change would appear to be more important than its magnitude.
Climate Instability and Hominid Brain Evolution
http://www.williamcalvin.com/1990s/1998AGU.htm
as well as the more 'political' effort (quite remarkable for its time) by Engels on the importance of labor on human brain development, developed with minimal fossil evidence, but still "a masterpiece of the dialectical method"
http://www.marxist.com/scienceandtech/HumanDevelopment.html