> Yep, if you can make them "aliens" ....
> then the barriers to killing them seem to fall quite rapidly. Presumably
> this is due to our omnivore heritage where if there weren't enough
> edible plants around, we ate meat to survive. There is even an
> argument (I'm not sure how well founded), that access to high density
> energy sources (such as bone marrow) was a requirement for a high
> energy consumption brain to evolve.
Anthropological theories suggest that a high quality diet was/is essential for the evolution of the Homo brain. Doubling of brain volume (800ml to ~1700ml) with maintenance of body mass and concomitant loss of gut size accompanied several dietary adaptations. Brain tissue comprises ~ 2% of body weight, however it consumes ~20% of total energy costs. I believe that heart, liver and testicular tissue are also high energy consumption organs.
High caloric density of diet was achieved by changing from a diet high in
leaves and woody plants to one of vertebrates, seeds and nuts. This met the
increased energy needs of the brain and increased digestibility demands of a
Food preparation and cooking are also thought to have compensated for the diminished gut capacity.
Dietary manipulation whether for weight control, longevity, body building or other goals, should therefore give consideration to both short term and long term costs.