As far as I know a lot of vegans for example draw the line at a specific set of complexity of the being. Usually the property “has a central nervous system” is sufficient, which is why some vegans even eat oysters. The wording “sentience” is also used often.
The argumentation is also that emotions are tied to higher processing capabilities. A lot of animals fear joy, pain can get sad etc… Plants don’t. Reactions of plants to external stimuli are rather very primitive reflexes than the result of active processing and reflection about stimuli, i.e. thinking, which is something only observed in animals with brains.
Don’t pin me down on that, I’m not a vegan. That’s just something I picked up through discussions with them.
I simply don’t know enough about nutrition to understand whether or not humans can be ‘maximally healthy’ on a vegetarian or vegan or pescatarian or w/e diet
Idk what a “w/e diet” is, nor can I speak about pescetarians. But from what I’ve read it is perfectly possible to live a long and healthy life on a purely plant-based diet (respectively non-animal-based, bc mushrooms are not plants).
I can point you towards scientific literature on that topic if you would like to have some assistance.
It makes sense if you think about it that way:
What do we get from eating meat for example? What is it, that makes it somehow valuable for our bodies? What stuff is inside food in general which makes us need to eat?
It’s a bunch of specific chemicals, which we have come to name “nutrients”. You don’t need the flesh of the animal per se, you need the iron, the fats, the proteins, vitamins, minerals et cetera. We humans need a specific set of those nutrients in a specific amount in order to maintain a healthy and functioning body (also influenced by individual factors like whether someone has iron resorbtion issues or if someone is a child or old or pregnant or an athlete or whatever). Other animals require different amounts and possibly also different sets of nutrients.
The question for us is now whether we can get those nutrients from purely non-animal sources. And the answer is: yes, we can. That doesn’t mean eating only vegs will be healthy in the long run, as you probably need to supplement vitamin B12 and possibly more. But those supplements can be made from purely non-animal sources.
It does make me wonder if having some cows that wander around eating grass and killing one or two of the herd periodically is really worse from a moral standpoint than covering entire ecosystems in solar panels to run the scaled up meat labs.
If you are concerned about ecosystems, you know that the animal industry is one of the major contributors to climate change, right? And the fact that we use a huge chunk of agricultural land to grow animal food? In the EU alone about 71 % of agriculture is dedicated to feed animals. Source for the latter.
Furthermore, solar panels are not the only means of energy production. (And those are and should be regulated according to approrpiate environmental laws such that sensitive ecosystems are sufficiently protected.) There are also plenty of other renewables and concepts to meet demands such as rooftops covered in solar panels, wind turbines etc…
From an ecological perspective it would be best if we completely stopped producing animal based products.