Interesting topic.
We humans tend to value the life of a creature based on (i) its size, (ii) its intelligence, (iii) life-time expectancy, (iv) its appearance/shape/"looks", (v) how much we (humans) are able to relate to this creature, and (vi) what purpose in nature this creature has.
So, first, imagine a creature with the following features;
- About the same size as a human.
- Highly intelligent creature
- This creature is expected to have a very long life (~ 100 years)
- Humans think this creature has a somewhat cute/attractive appearance.
- Humans can relate to this creature, it's behavior has similarities etc...
- This creature is of important to nature.
Then, imagine a creature with these features;
- A very little creature, say a 1x1x1cm.
- Not at all intelligent, and not really aware of its environment.
- Expected life-time is less than 6 months.
- Humans think of this creature as gross/ugly/disgusting/unattractive.
- Humans cannot relate to this creature, it's behavior is distinctively different...
- This creature is not of important to nature.
... Which life do you value more?
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In the end though, it's all about the "compassion & sympathy for our own", and being able to relate. We value human life more than animal life simply because we are human. It's WE, and it's THEM.
/thread